CMP Journal 2025-03-01
Statistics
arXiv: 63
arXiv
Dispersion and losses of plasmons along simple metasurfaces: the analysis of dispersion equations
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-28 20:00 EST
The flat metasurfaces described by tensor surface conductivity, the transverse size of which is small compared to the wavelength, are considered. In this case, we introduce two-dimensional surface conductivity for them, as well as for infinitely thin conductive sheets of graphene type. The method of Green's tensor functions of electrodynamics connecting fields and current densities, as well as the mode matching technique, are used. Conductive films on substrates are considered, including layered substrates of finite thickness with periodic layers and infinite substrates, as well as gradient substrates with a dependence of the dielectric constant on the thickness. Two-dimensional periodic structures of conductive films and dielectric films doped with nanoparticles are also analyzed. The possibility of applying the method to diffraction of surface plasmons on metasurface inhomogeneities is analyzed.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
On nonlinear graphene response on monochromatic electromagnetic wave in the form as generation of harmonics
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-28 20:00 EST
We consider the linear and nonlinear response of a weighted graphene sheet under the normal incidence of a plane electromagnetic wave in the form of a quasi-monochromatic pulse of long duration with a sharp edge and harmonic filling. The generation of odd harmonics in the reflected and transmitted spectra is obtained. The coefficient of transformation of the first harmonic into the third harmonic at a frequency of 10 Hz is of the order of 10-3. We use perturbative theory based on the quantum Wallace strong coupling model with field amplitude expansion and integration over the entire Brillouin zone (BZ), solving the kinetic Boltzmann equation with a collision integral in the Bhatnagar-Gross-Crook (BGK) form. The electromagnetic field is considered classically, while its vector potential changes the quasi-pulse in the dispersion equation.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
The Strain Impact on Weyl Semimetals
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Weyl semimetals are a class of topological semimetals defined by a Chern number as their topological invariant. These materials exhibit unique properties, such as transverse topological currents and anomalous magnetoelectric responses, making them promising candidates for device this http URL thesis explores the effects of strain on the electronic properties of Weyl semimetals using both toy models and first-principles calculations, specifically density functional theory (DFT) combined with the Wannier method. We investigated the strain effects on two-band tight-binding toy models by tuning their hopping integrals. To connect these models to real materials, we derived a tight-binding Hamiltonian from DFT combined with Wannier functions and analyzed the surface states and density of states under varying strain conditions. Our results reveal that both tensile and compressive strains significantly alter the electronic structure of TaAs, potentially inducing topological phase transitions. Specifically, tensile strain along the [100] direction leads to the transformation and eventual disappearance of Fermi arcs, while compressive strain results in the formation of complex surface states, suggesting the emergence of a new phase at higher strain levels.
Materials Science (cond-mat.mtrl-sci)
14 figures, 56 pages
Effects of Galactic Irradiation on Thermal and Electronic Transport in Tungsten
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
C.Ugwumadu, D. A. Drabold, R. Tutchton
The impact of irradiation on the thermal and electronic properties of materials is a persistent puzzle, particularly defect formation at the atomic and nanoscales. This work examines the nanoscale effects of low-energy irradiation on tungsten (W), focusing on defect-induced modifications to thermal and electronic transport. Using the Site-Projected Thermal Conductivity (SPTC) method [A. Gautam et al. PSS-RRL, 2400306, 2024], we analyze bulk and twin-grain boundary W with vacancy defects based on the Norgett-Robinson-Torrens displacements per atom (NRT-dpa) model. SPTC provides a detailed prediction of post-cascade spatial thermal conductivity distribution. We estimate electronic conductivity activity using the "N2 method" [K. Nepal et al. Carbon, 119711, 2025] to explore the consequences of vacancies and grain boundaries, highlighting the defect-dependent nature of charge transport behavior. These findings offer high-resolution insights into irradiation-driven transport phenomena, with implications for space-exposed materials and nanoscale thermal/electronic management.
Materials Science (cond-mat.mtrl-sci), Disordered Systems and Neural Networks (cond-mat.dis-nn)
't Hooft anomalies in metals
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-28 20:00 EST
I review some recent results on understanding the physics of metals in an exact non-perturbative way through the powerful field-theoretic concepts of emergent symmetries and 't Hooft anomalies. A 't Hooft anomaly is a discrete topological property that quantum field theories with global symmetries can have. I explain how many of the properties of metals can in fact be viewed as direct consequences of the anomaly. This allows a structural understanding of metals, including non-Fermi liquids, to be obtained even in the absence of any exact solution for the strongly coupled dynamics. I then outline the main limitations and outstanding questions.
Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Theory (hep-th)
Review article, to appear in "Annual Review of Condensed Matter Physics". Comments welcome. 21 pages
Band Renormalization, Quarter Metals, and Chiral Superconductivity in Rhombohedral Tetralayer Graphene
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-28 20:00 EST
Guillermo Parra-Martinez, Alejandro Jimeno-Pozo, Vo Tien Phong, Hector Sainz-Cruz, Daniel Kaplan, Peleg Emanuel, Yuval Oreg, Pierre A. Pantaleon, Jose Angel Silva-Guillen, Francisco Guinea
Recently, exotic superconductivity emerging from a spin-and-valley-polarized metallic phase has been observed in rhombohedral tetralayer graphene. To explain this finding, we study the role of electron-electron interactions in determining flavor symmetry breaking, using the Hartree Fock (HF) approximation, and also superconductivity driven by repulsive interactions. Though mean field HF correctly predicts the isospin flavors and reproduces the experimental phase diagram, it overestimates the band renormalization near the Fermi energy and suppresses superconducting instabilities. To address this, we introduce a physically motivated scheme that includes internal screening in the HF calculation. Superconductivity arises in the spin-valley polarized phase for a range of electric fields and electron doping. Our findings reproduce the experimental observations and reveal a \(p\)-wave, finite-momentum, time-reversal symmetry broken superconducting state, encouraging further investigation into exotic phases in graphene multilayers.
Strongly Correlated Electrons (cond-mat.str-el)
7 pages, 4 figures, supplementary material. Comments are welcome
Probing Green's Function Zeros by Co-tunneling through Mott Insulators
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-28 20:00 EST
Carl Lehmann, Lorenzo Crippa, Giorgio Sangiovanni, Jan Carl Budich
Quantum tunneling experiments have provided deep insights into basic excitations occurring as Green's function poles in the realm of complex quantum matter. However, strongly correlated quantum materials also allow for Green's functions zeros (GFZ) that may be seen as an antidote to the familiar poles, and have so far largely eluded direct experimental study. Here, we propose and investigate theoretically how co-tunneling through Mott insulators enables direct access to the shadow band structure of GFZ. In particular, we derive an effective Hamiltonian for the GFZ that is shown to govern the co-tunneling amplitude and reveal fingerprints of many-body correlations clearly distinguishing the GFZ structure from the underlying free Bloch band structure of the system. Our perturbative analytical results are corroborated by numerical data both in the framework of exact diagonalization and matrix product state simulations for a one-dimensional model system consisting of a Su-Schrieffer-Heeger-Hubbard model coupled to two single level quantum dots.
Strongly Correlated Electrons (cond-mat.str-el)
22 pages, 7 figures
Theta electromagnetism in quantum spin ice: Microscopic analysis of improper symmetries
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-28 20:00 EST
Gautam K. Naik, Jonathan N. Hallén, Chris R. Laumann
\(U(1)\) gauge theories, including conventional Maxwell electromagnetism, allow \(\theta\)-terms when parity and time-reversal symmetry are broken. In condensed matter systems, the physics of \(\theta\) as a magnetoelectric response has been explored extensively within the context of topological insulators and multiferroics. We show how \(\theta\)-terms can arise in the internal dynamics of the emergent electromagnetism in a \(U(1)\) quantum spin liquid. In its Coulomb phase, the minimal model of pyrochlore quantum spin ice is governed by a six-spin ring exchange Hamiltonian. We identify the next-order contribution to the microscopic Hamiltonian when parity, time-reversal, and all improper spatial symmetries are broken -- a seven-spin term which leads to a two-parameter lattice gauge theory with a \(\theta\)-electromagnetic phase. We derive how the seven-spin term is generated perturbatively within each of the three symmetry classes of short-range pyrochlore spin ice. Within a complete microscopic symmetry analysis, we find that the most general nearest-neighbor Hamiltonians fail to generate the seven-spin term, and one must include next-nearest-neighbor interactions to obtain an emergent \(\theta\). Using gauge mean-field theory we compute additional contributions to the \(\theta\)-term from the spinon sector. Finally, we determine the conditions required for an internal \(\theta\)-term to generate a significant external magnetoelectic response.
Strongly Correlated Electrons (cond-mat.str-el)
26 pages, 5 figures
Single-band square lattice Hubbard model from twisted bilayer C568
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-28 20:00 EST
Zhu-Xi Luo, Ashvin Vishwanath, Toshikaze Kariyado
We propose twisted homobilayer of a carbon allotrope, C\(_{568}\), to be a promising platform to realize controllable square lattice single-band extended Hubbard model. This setup has the advantage of a widely tunable \(t'/t\) ratio without adding external fields, and the intermediate temperature \(t\ll T\ll U\) regime can be easily achieved. We first analyze the continuum model obtained from symmetry analysis and first-principle calculations, and calculate the band structures. Subsequently, we derive the corresponding tight-binding models and fit the hopping parameters as well as the Coulomb interactions. When displacement field is applied, anisotropic nearest neighbor hoppings can further be achieved. If successfully fabricated, the device could be an important stepping stone towards understanding high-temperature superconductivity.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Superconductivity (cond-mat.supr-con)
9 pages, 10 figures
Signatures of collective photon emission and ferroelectric ordering of excitons near their Mott insulating state in a WSe\(_2\)/WS\(_2\) heterobilayer
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-28 20:00 EST
Luka Matej Devenica, Zach Hadjri, Jan Kumlin, Runtong Li, Weijie Li, Daniel Suarez Forrero, Valeria Vento, Nicolas Ubrig, Song Liu, James Hone, Kenji Watanabe, Takashi Taniguchi, Thomas Pohl, Ajit Srivastava
Spontaneous symmetry breaking, arising from the competition of interactions and quantum fluctuations, is fundamental to understanding ordered electronic phases. Although electrically neutral, optical excitations like excitons can interact through their dipole moment, raising the possibility of optically active ordered phases. The effects of spontaneous ordering on optical properties remain largely unexplored. Recent observations of the excitonic Mott insulating state in semiconducting moiré crystals make them promising for addressing this question. Here, we present evidence for an in-plane ferroelectric phase of dipolar moiré excitons driven by strong exciton-exciton interactions. We discover a surprising speed-up of photon emission at late times and low densities in excitonic decay. This counterintuitive behavior is attributed to collective radiance, linked to the transition between disordered and symmetry-broken ferroelectric phases of moiré excitons. Our findings provide first evidence for strong dipolar inter-site interactions in moiré lattices, demonstrate collective photon emission as a probe for moiré quantum materials, and pave the way for exploring cooperative optical phenomena in strongly correlated systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
Evidence for strongly correlated superconductivity in La\(_3\)Ni\(_2\)O\(_7\) from first principles
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-28 20:00 EST
Daan Verraes, Tom Braeckevelt, Nick Bultinck, Veronique Van Speybroeck
We conduct first-principles simulations of pressurized La\(_3\)Ni\(_2\)O\(_7\), a material in which a recent series of experiments has found signs of high-temperature superconductivity. In the pressure range where superconductivity is observed, we find a significant increase in the Hubbard U parameter (i.e. the strength of on-site repulsion) for the maximally localized Wannier states comprising the density functional theory (DFT) bands crossing the Fermi energy. We attribute this increase in U to reduced screening by the nearby La 5d bands - an effect that is sensitive to the pressure-driven crystal structure. Our results therefore indicate that the superconducting region in the La\(_3\)Ni\(_2\)O\(_7\) phase diagram coincides with a region of enhanced electronic correlations. Ab initio molecular dynamics simulations extend these trends to finite temperatures, providing insights into the experimentally observed transition lines. Finally, we explore intrinsic chemical pressure using DFT simulations of Ac\(_3\)Ni\(_2\)O\(_7\).
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
Intercalated structures formed by platinum on epitaxial graphene on SiC(0001)
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Letizia Ferbel, Stefano Veronesi, Antonio Rossi, Stiven Forti, Camilla Coletti, Stefan Heun
Graphene on SiC intercalated with two-dimensional metal layers, such as Pt, offers a versatile platform for applications in spintronics, catalysis, and beyond. Recent studies have demonstrated that Pt atoms can intercalate at the heterointerface between SiC(0001) and the C-rich \((6\sqrt{3}\times6\sqrt{3})\)R30° reconstructed surface (hereafter referred as the buffer layer). However, key aspects such as intercalated phase structure and intercalation mechanisms remain unclear. In this work, we investigate changes in morphology, chemistry, and electronic structure for both buffer layer and monolayer graphene grown on SiC(0001) following Pt deposition and annealing cycles, which eventually led to Pt intercalation at temperatures above 500°C. Atomic-resolution imaging of the buffer layer reveals a single intercalated Pt layer that removes the periodic corrugation of the buffer layer, arising from partial bonding of C-atoms with Si-atoms of the substrate. In monolayer graphene, the Pt-intercalated regions exhibit a two-level structure: the first level corresponds to a Pt layer intercalated below the buffer layer, while the second level contains a second Pt layer, giving rise to a \((12\times12)\) superstructure relative to graphene. Upon intercalation, Pt atoms appear as silicides, indicating a reaction with Si atoms from the substrate. Additionally, charge neutral \(\pi\)-bands corresponding to quasi-free-standing monolayer and bilayer graphene emerge. Analysis of multiple samples, coupled with a temperature-dependent study of the intercalation rate, demonstrates the pivotal role of buffer layer regions in facilitating the Pt intercalation in monolayer graphene. These findings provide valuable insight into Pt intercalation, advancing the potential for applications.
Materials Science (cond-mat.mtrl-sci)
Carbon 234 (2025) 119989
A generalized calculation of the rate independent single crystal yield surface
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Matthew Kasemer, Paul R. Dawson
In this paper, we discuss a method to calculate the topology of the rate independent single crystal yield surface for materials with arbitrary slip systems and arbitrary slip strengths. We describe the general problem, as motivated by Schmid's law, and detail the calculation of hyperplanes in deviatoric stress space, \(\mathbb{D}^5\), which describe the criteria for slip on individual slip systems. We focus on finding the intersection of five linearly independent hyperplanes which represent stresses necessary to satisfy the criteria for general plastic deformation. Finally, we describe a method for calculating the inner convex hull of these intersection points, which describe the vertices of the five dimensional polytope that represents the single crystal yield surface. Our method applies to arbitrary crystal structure, allowing for an arbitrary number and type of slip systems and families, considers plastic anisotropy via inter- and intra-family strength anisotropy, and further considers strength anisotropy between slip in the positive and negative direction. We discuss the calculation and possible applications, and share a computational implementation of the calculation of the single crystal yield surface.
Materials Science (cond-mat.mtrl-sci)
19 pages, 10 figures
Comment on "InAs-Al hybrid devices passing the topological gap protocol", Microsoft Quantum, Phys. Rev. B 107, 245423 (2023)
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-28 20:00 EST
The topological gap protocol (TGP) is presented as "a series of stringent experimental tests" for the presence of topological superconductivity and associated Majorana bound states. Here, we show that the TGP, 'passed' by Microsoft Quantum [PRB 107, 245423 (2023)], lacks a consistent definition of 'gap' or 'topological', and even utilises different parameters when applied to theoretical simulations compared to experimental data. Furthermore, the TGP's outcome is sensitive to the choice of magnetic field range, bias voltage range, data resolution, and number of cutter voltage pairs - data parameters that, in PRB 107, 245423 (2023), vary significantly, even for measurements of the same device. As a result, the core claims of PRB 107, 245423 (2023) are primarily based on unexplained measurement choices and inconsistent definitions, rather than on intrinsic properties of the studied devices. As such, Microsoft Quantum's claim in PRB 107, 245423 (2023) that their devices have a "high probability of being in the topological phase" is not reliable and must be revisited. Our findings also suggest that subsequent studies, e.g. Nature 638, 651-655 (2025), that are based on tuning up devices via the TGP are built on a flawed protocol and should also be revisited.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Superconductivity (cond-mat.supr-con), Quantum Physics (quant-ph)
Comment on arXiv:2207.02472. 9 Figures, 1 Table, several code excerpts. Feedback welcome
Anisotropy-Driven Quantum Level-Crossing in Spin-1 Heisenberg Dimers: Applications in Quantum Stirling Machines
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-28 20:00 EST
Bastian Castorene, Vinicius Gomez de Paula, Francisco J. Peña, Clebson Cruz, Mario Reis, Patricio Vargas
This work explores the thermodynamic performance of a quantum Stirling heat engine implemented with an anisotropic spin-1 Heisenberg dimer as the working medium. Using the Hamiltonian of the system, we analyze the interplay of anisotropy, magnetic field, and exchange interactions and their influence on the energy spectrum and the quantum level crossing. Our results reveal that double-degenerate point (DDP) and a triple-degenerate point (TDP) play pivotal roles in shaping the operational regimes and efficiency of the quantum Stirling engine. At those points, the Carnot efficiency reaches higher work output and enhanced stability, making it a robust candidate for optimal thermodynamic performance. These findings highlight the potential of anisotropic spin systems as viable platforms for quantum heat engines and contribute to advancing the field of quantum thermodynamics.
Statistical Mechanics (cond-mat.stat-mech)
6 Figures
An Analysis of First- and Second-Order Optimization Algorithms in Variational Monte Carlo
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-28 20:00 EST
Ruojing Peng, Garnet Kin-Lic Chan
Many quantum many-body wavefunctions, such as Jastrow-Slater, tensor network, and neural quantum states, are studied with the variational Monte Carlo technique, where stochastic optimization is usually performed to obtain a faithful approximation to the ground-state of a given Hamiltonian. While first order gradient descent methods are commonly used for such optimizations, recent second order optimization formulations offer the potential of faster convergence under certain theoretical conditions, but with a similar cost per sample to first order methods. However, the relative performance of first order and second order optimizers is influenced in practice by many factors, including the sampling requirements for a faithful optimization step, the influence of wavefunction quality, as well as the wavefunction parametrization and expressivity. Here we analyze these performance characteristics of first order and second order optimization methods for a variety of Hamiltonians, with the additional context of understanding the scaling of these methods (for good performance) as a function of system size. Our findings help clarify the role of first order and second order methods in variational Monte Carlo calculations and the conditions under which they should respectively be used. In particular, we find that unlike in deterministic optimization, where closeness to the variational minimum determines the suitability of second order methods, in stochastic optimization the main factor is the overall expressivity of the wavefunction: second order methods lead to an overall reduction in cost relative to first order methods when the wavefunction is sufficiently expressive to represent the ground-state, even when starting away from the ground state. This makes second order methods an important technique when used with wavefunctions with arbitrarily improvable accuracy.
Strongly Correlated Electrons (cond-mat.str-el), Disordered Systems and Neural Networks (cond-mat.dis-nn)
21 pages, 17 figures
Odd Active Solids: Vortices, Velocity Oscillations and Dissipation-Free Modes
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-28 20:00 EST
Lorenzo Caprini, Umberto Marini Bettolo Marconi
A wide range of physical and biological systems, including colloidal magnets, granular spinners, and starfish embryos, are characterized by strongly rotating units that give rise to odd viscosity and odd elasticity. These active systems can be described using a coarse-grained model in which the pairwise forces between particles include a transverse component compared to standard interactions due to a central potential. These non-potential, additional forces, referred to as odd interactions, do not conserve energy or angular momentum and induce rotational motion. Here, we study a two-dimensional crystal composed of inertial Brownian particles that interact via odd forces and are in thermal contact with their environment. In the underdamped regime, the energy injected by odd forces can counteract dissipation due to friction, leading to quasi-dissipation-free excitations with finite frequency and wavelength. In the resulting non-equilibrium steady state, the system exhibits angular momentum and velocity correlations. When the strength of the odd forces exceeds a certain threshold or friction is too low, a crystal with only harmonic springs becomes linearly unstable due to transverse fluctuations. This instability can be mitigated by introducing nonlinear central interactions, which suppress the divergence of short-wavelength velocity fluctuations and allows us to numerically explore the linearly unstable regime. This is characterized by pronounced temporal oscillations in the velocity featuring the existence of vortex structures and kinetic temperature values larger than the thermal temperature.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
Anomalous Long-range Hard-wall Repulsion between Polymers in Solvent Mixtures and Its Implication for Biomolecular Condensates
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-28 20:00 EST
The system of polymers in solvent mixtures is a widely-used model to represent biomolecular condensates in intracellular environments. Here, we apply a variational theory to control the center-of-mass of two polymers and perform the first quantification of their interactions in solvent mixtures. Even both solvent and cosolvent are good to the polymer, we demonstrate that strong polymer-cosolvent affinity induces the formation of a single-chain condensate. Even though all the molecular interactions are soft, the potential of mean force between two condensates exhibits an anomalous feature of long-range hard-wall repulsion, which cannot be categorized into any existing types of inter-chain interactions. This repulsion is enhanced as either the affinity or the bulk cosolvent fraction increases. The underlying mechanism is cosolvent regulation manifested as a discontinuous local condensation of cosolvent. The hard-wall repulsion provides a kinetic barrier to prevent coalescence of condensates and hence highlights the intrinsic role of proteins as a cosolvent in stabilizing biomolecular condensates.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech), Chemical Physics (physics.chem-ph)
Quantitative description of strongly correlated materials by combining downfolding techniques and tensor networks
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-28 20:00 EST
Daan Vrancken, Simon Ganne, Daan Verraes, Tom Braeckevelt, Lukas Devos, Jutho Haegeman, Veronique Van Speybroeck
We present a high-accuracy procedure for electronic structure calculations of strongly correlated materials. The approach involves downfolding the full Hilbert space into a low-energy subspace that captures the most significant electron correlations, leading to an effective Hubbard model. This generalized model is then solved using tensor network methods. Our work focuses on one-dimensional and quasi-one-dimensional materials, for which we employ the machinery of matrix product states. We apply this framework to the conjugated polymers trans-polyacetylene and polythiophene, as well as the quasi-one-dimensional charge-transfer insulator Sr2CuO3. The predicted band gaps exhibit quantitative agreement with state-of-the-art computational techniques and experimental measurements. Beyond band gaps, tensor networks provide access to a wide range of physically relevant properties, including spin magnetization and various excitation energies. Their flexibility supports the implementation of complex Hamiltonians with longer-range interactions, while the bond dimension enables systematic control over accuracy. Furthermore, the computational cost scales efficiently with system size, demonstrating the framework's scalability.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
29 pages, 13 figures, 11 tables
Anomalous spin-optical helical effect in Ti-based kagome metal
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-28 20:00 EST
Federico Mazzola, Wojciech Brzezicki, Chiara Bigi, Armando Consiglio, Luciano Jacopo D' Onofrio, Maria Teresa Mercaldo, Adam Kłosiński, François Bertran, Patrick Le Fèvre, Oliver J. Clark, Mark T. Edmonds, Manuel Tuniz, Alessandro De Vita, Vincent Polewczyk, Jeppe B. Jacobsen, Henrik Jacobsen, Jill A. Miwa, Justin W. Wells, Anupam Jana, Ivana Vobornik, Jun Fujii, Niccolò Mignani, Narges Samani Tarakameh, Alberto Crepaldi, Giorgio Sangiovanni, Anshu Kataria, Tommaso Morresi, Samuele Sanna, Pietro Bonfá, Brenden R. Ortiz, Ganesh Pokharel, Stephen D. Wilson, Domenico Di Sante, Carmine Ortix, Mario Cuoco
The kagome lattice stands as a rich platform for hosting a wide array of correlated quantum phenomena, ranging from charge density waves and superconductivity to electron nematicity and loop current states. Direct detection of loop currents in kagome systems has remained a formidable challenge due to their intricate spatial arrangements and the weak magnetic field signatures they produce. This has left their existence and underlying mechanisms a topic of intense debate. In this work, we uncover a hallmark reconcilable with loop currents: spin handedness-selective signals that surpass conventional dichroic, spin, and spin-dichroic responses. We observe this phenomenon in the kagome metal CsTi\(_3\)Bi\(_5\) and we call it the anomalous spin-optical helical effect. This effect arises from the coupling of light' s helicity with spin-orbital electron correlations, providing a groundbreaking method to visualize loop currents in quantum materials. Our discovery not only enriches the debate surrounding loop currents but also paves the way for new strategies to exploit the electronic phases of quantum materials via light-matter interaction.
Strongly Correlated Electrons (cond-mat.str-el)
In-plane Ising superconductivity revealed by exchange interactions
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-28 20:00 EST
Junyi Yang, Changjiang Liu, Xianjing Zhou, John Pearson, Alexey Suslov, Dafei Jin, Jidong S. Jiang, Ulrich Welp, Michael R. Norman, Anand Bhattacharya
Two-dimensional superconductors with spin-textured Fermi surfaces can be a platform for realizing unconventional pairing and are of substantial interest in the context of quantum information science, and superconducting spintronics/orbitronics. We find that the superconducting 2D electron gas (2DEG) formed at EuOx/KTaO3 (110) interfaces, where the EuOx is magnetic, has a spin-texture with an unusual in-plane Ising like uniaxial anisotropy that is revealed in measurements of the in-plane critical field in the superconducting state, as well as from quantum corrections to the magnetoresistance in the normal state. This spin texture is not evident in AlOx/KTaO3 (110) where the overlayer is non-magnetic. Our results are consistent with a highly anisotropic spin-textured Fermi surface in 2DEGs formed at the KTaO3 (110) interface that is hidden from external magnetic fields due to a near cancellation between orbital and spin moments but revealed by exchange interactions of the electrons in the 2DEG with Eu moments near the EuOx/KTaO3 (110) interface. Our findings demonstrate that magnetic overlayers provide a unique probe of spin textures and related phenomena in heterostructures.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
17 pages, 5 figures
Confined colloidal droplets dry to form circular mazes
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-28 20:00 EST
Ilaria Beechey-Newman, Natalia Kizilova, Andreas Andersen Hennig, Eirik Grude Flekkøy, Erika Eiser
During drying, particle-laden sessile droplets will leave so-called coffee-stain rings behind. This phenomenon is well-known and well-understood (Deegan et al., Nature {},827-829 (1997)). Here we show that when particle-laden droplets confined in a slit are allowed to evaporate very slowly, they do not deposit coffee rings, but form a surprisingly intricate, circular maze-like pattern. We present experiments that illustrate this pattern formation and discuss the factors that determine when such patterns can form. We are not aware of reports of natural examples of the formation of such beautiful patterns under confinement, although it seems likely that they exist.
Soft Condensed Matter (cond-mat.soft)
Translational diffusion in supercooled water at and near the glass transition temperature -- 136 K
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-28 20:00 EST
Greg A. Kimmel, Megan K. Dunlap, Kirill Gurdumov, R. Scott Smith, Bruce D. Kay
The properties of amorphous solid water at and near the calorimetric glass transition temperature, \(T_{g}\), of 136 K have been debated for years. One hypothesis is that water turns into a "true" liquid at \(T_{g}\) (i.e., it becomes ergodic) and exhibits all the characteristics of an ergodic liquid, including translational diffusion. A competing hypothesis is that only rotational motion becomes active at \(T_{g}\), while the "real" glass transition in water is at a considerably higher temperature. To address this dispute, we have investigated the diffusive mixing in nanoscale water films, with thicknesses up to ~100 nm, using infrared (IR) spectroscopy. The experiments used films that were composed of at least 90% \(H_{2}O\) with \(D_{2}O\) making up the balance and were conducted in conditions where H/D exchange was essentially eliminated. Because the IR spectra of multilayer \(D_{2}O\) films (e.g., thicknesses of ~3 - 6 nm) embedded within thick \(H_{2}O\) films are distinct from the spectrum of isolated \(D_{2}O\) molecules within \(H_{2}O\), the diffusive mixing of (initially) isotopically layered water films could be followed as a function of annealing time and temperature. The results show that water films with total thicknesses ranging from ~20 to 100 nm diffusively mixed prior to crystallization for temperatures between 120 and 144 K. The translational diffusion had an Arrhenius temperature dependence with an activation energy of 40.8 kJ/mol, which indicates that water at and near \(T_{g}\) is a strong liquid. The measured diffusion coefficient at 136 K is 6.25 x 10\(^{-21} m^{2}/s\).
Soft Condensed Matter (cond-mat.soft)
Atomistic insights into solid solution strengthening: size misfit versus stiffness misfit
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Aoyan Liang, Nicolas Bertin, Xinran Zhou, Sylvie Aubry, Vasily V. Bulatov
Used for centuries to enhance mechanical properties of materials, solid solution strengthening (SSS) is a classical metallurgical method in which small amounts of impurity elements are added to a base metal. Developed for dilute alloys, classical theories of SSS are presently challenged by the ongoing explosive development of complex concentrated alloys (CCA) in which all component elements are present in nearly equal fractions. Here we develop a method of computational alchemy in which interatomic interactions are modified to continuously and systematically vary two key parameters defining SSS, atomic size misfit and elastic stiffness misfit, over a maximally wide range of misfit values. The resulting model alloys are subjected to massive Molecular Dynamics simulations reproducing full complexity of plastic strength response in concentrated single-phase body-centered cubic solid solutions. At variance with views prevailing in the literature, our computational experiments show that stiffness misfit can contribute to SSS on par if not more than size misfit. Furthermore, depending on exactly how they are combined, the two misfits can result in synergistic or antagonistic effect on alloy strengthening. In contrast to real CCAs in which every constituent element comes with its specific combination of atomic size and elastic stiffness, our alchemical model alloys sample the space of misfit parameters continuously thus augmenting the much more constrained and inevitably spotty experimental exploration of the CCA design space. Taking advantage of unique to our approach ability to define alloy misfit parameters, our computational study demonstrates how useful insights can be gained from intentionally unrealistic alchemical models. Rather than practical recommendation for alloy design, our computational experiments should be regarded as a proving ground for further SSS theory development.
Materials Science (cond-mat.mtrl-sci)
23 pages, 9 figures, submitted to Matter
Spectral Analysis of Representational Similarity with Limited Neurons
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-02-28 20:00 EST
Hyunmo Kang, Abdulkadir Canatar, SueYeon Chung
Measuring representational similarity between neural recordings and computational models is challenging due to constraints on the number of neurons that can be recorded simultaneously. In this work, we investigate how such limitations affect similarity measures, focusing on Canonical Correlation Analysis (CCA) and Centered Kernel Alignment (CKA). Leveraging tools from Random Matrix Theory, we develop a predictive spectral framework for these measures and demonstrate that finite neuron sampling systematically underestimates similarity due to eigenvector delocalization. To overcome this, we introduce a denoising method to infer population-level similarity, enabling accurate analysis even with small neuron samples. Our theory is validated on synthetic and real datasets, offering practical strategies for interpreting neural data under finite sampling constraints.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Machine Learning (cs.LG), Neurons and Cognition (q-bio.NC)
First-Principles Framework for the Prediction of Intersystem Crossing Rates in Spin Defects: The Role of Electron Correlation
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Yu Jin, Jinsoo Park, Marquis M. McMillan, Daniel Donghyon Ohm, Corrie Barnes, Benjamin Pingault, Christopher Egerstrom, Benchen Huang, Marco Govoni, F. Joseph Heremans, David D. Awschalom, Giulia Galli
Optically active spin defects in solids are promising platforms for quantum technologies. Here, we present a first-principles framework to investigate intersystem crossing processes, which represent crucial steps in the optical spin-polarization cycle used to address spin defects. Considering the nitrogen-vacancy center in diamond as a case study, we demonstrate that our framework effectively captures electron correlation effects in the calculation of many-body electronic states and their spin-orbit coupling and electron-phonon interactions, while systematically addressing finite-size effects. We validate our predictions by carrying out measurements of fluorescence lifetimes, finding excellent agreement between theory and experiments. The framework presented here provides a versatile and robust tool for exploring the optical cycle of varied spin defects entirely from first principles.
Materials Science (cond-mat.mtrl-sci), Quantum Physics (quant-ph)
First-principles study on Pr-doped Bilayer Nickelate La3Ni2O7
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-28 20:00 EST
Zihao Huo, Peng Zhang, Haoliang Shi, Xiaochun Yan, Defang Duan, Tian Cui
Recently, the Pr-doped Ruddlesden-Popper phase of bilayer nickelate La3Ni2O7 has been reported to exhibit a superconducting transition temperature (Tc) of 82.5 K and superconducting volume fraction of about 57 % at high pressure. However, the effect of Pr-doping on La3Ni2O7 remains unclear. Here, we studied the crystal structures and electronic properties of Pr-doped La3Ni2O7 at 0 and 15 GPa based on the first-principles calculations to explore the doping effect of Pr. Our findings indicate that the praseodymium atoms prefer to occupy the outer La-O layers site. We then investigated the evolution of crystal structures in both the ambient pressure phase and high pressure phase of La3Ni2O7 as a function of doping concentration, revealing inconsistent trends in their evolution with increasing doping levels. Finally, by fitting the bilayer two-orbital model, we propose that doping Pr may benefit for superconductivity of La3Ni2O7. These results not only can help the further experimental search of RP phase nickelate at lower pressure, but also provide helpful guide for understanding the effect of chemical pressure in isovalent doped RP phase nickelate superconductor.
Superconductivity (cond-mat.supr-con)
Manipulation of topological phase transitions and the mechanism of magnetic interactions in Eu-based Zintl-phase materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Bo-Xuan Li, Ziyin Song, Zhong Fang, Zhijun Wang, Hongming Weng
Various topological phases, including topological insulators, topological semimetals, and topological superconductors, along with the controllable topological phase transitions, have attracted considerable attention due to their promising applications in spintronics and quantum computing. In this work, we propose two distinct methods for manipulating topological phase transitions in magnetic materials. First, by varying the strength of electron correlation effects, we induce a series of topological state transitions within the EuM\(_2\)X\(_2\) (M = Zn, Cd; X = P, As, Sb) family of Zintl materials, including magnetic topological crystalline insulators (TCIs) and magnetic Dirac semimetals. Our findings indicate that strong electron correlation effects tend to influence the emergence of topological phases. Second, by reducing the electronegativity of the pnictogen X (from P to As and Sb), we observe a similar transition from trivial insulator to magnetic Dirac semimetal or magnetic TCI. This suggests that weaker electronegativity favors the emergence of topological phases. Furthermore, we establish a Heisenberg model to describe the magnetic interactions of the EuM\(_2\)X\(_2\) system, based on which we perform Monte Carlo simulations of specific heat and magnetic susceptibility, yielding Néel temperatures that perfectly match experimental data. This suggests that the local magnetic moment framework provides an accurate description of the magnetization behavior in this family of materials. This work provides the potential for the experimental manipulation of topological phase transitions and their possible applications, while also enhancing the understanding of the magnetic interactions within the EuM\(_2\)X\(_2\) system and offering a theoretical foundation for future applications in magnetism.
Materials Science (cond-mat.mtrl-sci)
13 pages, 9 figures
Realizing stable zig-zag polymeric nitrogen chains in P-N compounds
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Chengfeng zhang, Guo Chen, Yanfeng Zhang, Jie Zhang, Xianlong Wang
The zig-zag Nitrogen (N) chain similar to the Ch-N structure has long been considered a potential high energy density structure. However, all previously predicted zig-zag N chain structures similar to Ch-N exhibit imaginary frequencies in their phonon spectra at 0 GPa. Here, we conducted a systematic investigation of P-N compounds using first-principles calculations, uncovering a series of structurally similar stable phases, C2/m-PNx (x = 6, 8, 10, 12, 14), in which N forms zig-zag N chains similar to those in Ch-N. In P-N compounds, the longest zig-zag N chain that can theoretically remain stable under ambient pressure is the N chain composed of 14 N atoms in C2/m-PN14. If the N chain continues to grow, inter-chain vibrational imaginary frequencies will arise in the system. Notably, N chains with an even number of atoms are more likely to be energetically favorable. The five C2/m-PNx phases and one metastable phase (R-PN6) exhibit both remarkable stability and excellent detonability at ambient pressure, positioning them as promising candidates for high-energy-density materials. In addition, the R-PN6 is the first structure to stabilize the N6 ring through covalent bonding, with the covalent network contributing to its high hardness (47.59 GPa).
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
19 pages, 7 figures
Extracting intrinsic superconducting properties in intercalated layered superconductors using an extended 2D Tinkham model
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-28 20:00 EST
Yue Liu, Yuhang Zhang, Zouyouwei Lu, Dong Li, Yuki M. Itahashi, Zhanyi Zhao, Jiali Liu, Jihu Lu, Feng Wu, Kui Jin, Hua Zhang, Ziyi Liu, Xiaoli Dong, Zhongxian Zhao
Bulk two dimensional (2D) superconductivity has gained considerable attention due to its intricate interplay between symmetry breaking, nontrivial topology, 2D phase fluctuations, and unconventional superconductivity. However, certain intercalated layered superconductors, despite their short c-axis superconducting coherence length, have been misclassified as anisotropic three-dimensional (3D) superconductors. Here, we investigate (Li,Fe)OHFeSe superconductors with varying degrees of interlayer misalignment, revealing sample-dependent superconducting dimensionality while consistently observing Berezinskii Kosterlitz Thouless (BKT) transitions. To resolve this discrepancy, we develop an extended 2D Tinkham model that quantitatively captures the blurring effects induced by interlayer misalignment. We further demonstrate the validity of this model in both (Li,Fe)OHFeSe and cetyltrimethyl ammonium (CTA+) intercalated (CTA)0.5SnSe2 superconductors, highlighting its broad applicability. This work provides valuable insights into bulk 2D superconductivity and establishes an extended 2D Tinkham model for quantitatively extracting intrinsic superconducting properties in intercalated layered superconductors, particularly those exhibiting significant interlayer misalignments.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
Gate-Tunable Spin-to-Charge Conversion in Topological Insulator-Magnetic Insulator Heterostructures at Room Temperature
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-28 20:00 EST
Wenxuan Sun, Yequan Chen, Ruijie Xu, Wenzhuo Zhuang, Di Wang, Long Liu, Anke Song, Guozhong Xing, Yongbing Xu, Rong Zhang, Cui-Zu Chang, Xuefeng Wang
Over the past decade, topological insulators have received enormous attention for their potential in energy-efficient spin-to-charge conversion, enabled by strong spin-orbit coupling and spin-momentum locked surface states. Despite extensive research, the spin-to-charge conversion efficiency, usually characterized by the spin Hall angle ({}SH), remains low at room temperature. In this work, we employed pulsed laser deposition to synthesize high-quality ternary topological insulators (Bi0.1Sb0.9)2Te3 thin films on magnetic insulator Y3Fe5O12. We find that the value of {}SH reaches ~0.76 at room temperature and increases to ~0.9 as the Fermi level is tuned to cross topological surface states via electrical gating. Our findings provide an innovative approach to tailoring the spin-to-charge conversion in topological insulators and pave the way for their applications in energy-efficient spintronic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
19 pages, 11 figures, 1 table
Adv. Funct. Mater. 35, 2501880 (2025)
Ferroelectric Chirality-Driven Direction-Tunable and Spin-Invertible Corner States in 2D MOF-Based Magnetic Second-Order Topological Insulators
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Jialin Gong, Wei Sun, Yang Wu, Zhenzhou Guo, Shifeng Qian, Xiaotian Wang, Gang Zhang
Despite the rapid progress in predicting 2D magnetic second-order topological insulators (SOTIs), effective strategies for manipulating their spin-polarized corner states remain largely unexplored. The interplay between ferroelectricity, chirality, magnetism, and topology presents an untapped opportunity for controlling these corner states. Here, we propose a novel approach for tuning spin-polarized corner states in 2D magnetic SOTIs by inducing ferroelectric chirality in 2D metal-organic frameworks (MOFs) with intrinsic structural flexibility. Through symmetry analysis, we strategically replace pyrazine (pyz) ligands with 2-pyrazinolate (2-pyzol) ligands in the 2D MOF Cr(pyz)2, leading to the emergence of a new 2D magnetic SOTI, Cr(2-pyzol)2, which facilitates ferroelectric chirality controlled spin-polarized corner states in both spin channels. Through first-principle calculations, we demonstrate that Cr(2-pyzol)2 belongs to ferroelectric chiral systems, and its corner states can be directionally tuned in real space and spin-inverted in spin space upon ferroelectric chirality switching. Our work represents the first attempt to simultaneously manipulate corner states in both real space and spin space, offering a new strategy for integrating ferroelectric chirality into 2D MOF-based magnetic SOTIs.
Materials Science (cond-mat.mtrl-sci)
Machine-Learning Force Fields Reveal Shallow Electronic States on Dynamic Halide Perovskite Surfaces
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Frederico P. Delgado, Frederico Simões, Leeor Kronik, Waldemar Kaiser, David A. Egger
The spectacular performance of halide perovskites in optoelectronic devices is rooted in their favorable tolerance to structural defects. Previous studies showed that defects in these materials generate shallow electronic states that do not degrade device performance. However, how these shallow states persist amid the pronounced thermally-stimulated atomic dynamics on halide perovskite surfaces remains unknown. This work reveals that electronic states at surfaces of the prototypical CsPbBr\(_3\) variant are energetically distributed at room temperature, akin to well-passivated inorganic semiconductors, even when covalent bonds remain cleaved and undercoordinated. Specifically, a striking tendency for shallow surface states is found with approximately 70% of surface-state energies appearing within 0.2 eV or \({\approx}8k_\text{B}T\) from the valence-band edge. Furthermore, we show that even when surface states appear deeper in the gap, they are not energetically isolated and are less likely to act as traps. We achieve this result by accelerating first-principles calculations via machine-learning techniques and show that the unique atomic dynamics in these materials render the formation of deep electronic states at their surfaces unlikely. These findings reveal the microscopic mechanism behind the low density of deep defect states at dynamic halide perovskite surfaces, which is key to their exceptional performance in devices.
Materials Science (cond-mat.mtrl-sci)
Hysteretic responses of nanomechanical resonators based on crumpled few-layer graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-28 20:00 EST
Heng Lu, Chen Yang, Ce Zhang, YuBin Zhang, FengNan Chen, Yue Ying, Zhuo-Zhi Zhang, Xiang-Xiang Song, Guang-Wei Deng, Ying Yan, Joel Moser
Manipulating two-dimensional materials occasionally results in crumpled membranes. Their complicated morphologies feature an abundance of folds, creases and wrinkles that make each crumpled membrane unique. Here, we prepare four nanomechanical resonators based on crumpled membranes of few-layer graphene and measure their static response and the spectrum of their dynamic response. We tune both responses with a dc voltage applied between the membrane and an underlying gate electrode. Surprisingly, we find that all four resonators exhibit hysteretic responses as the gate voltage is increased and then decreased. Concomitant discontinuities in the static response and in the vibrational resonant frequencies indicate a sudden change in the shape and in the tensile strain of the membranes. We also find that the hystereses can be removed and regular responses can be restored by annealing the resonators. We hypothesize that the hysteretic nature of the responses may originate from an interplay between the rugged morphology of the membranes and adsorbates trapped within the confine of the folds.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
The following article has been submitted to Applied Physics Letters
Elongated vortex quantum droplets in binary Bose-Einstein condensates
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-02-28 20:00 EST
Guilong Li, Zibin Zhao, Rui Zhang, Zhaopin Chen, Bin Liu, Boris A. Malomed, Yongyao Li
Stability of elongated (``slender") quantum droplets (QDs) with embedded unitary and multiple vorticity is a problem that was not solved previously. In this work, we propose a solution which relies upon the use of the spatial modulation of the inter-species scattering length in the binary Bose-Einstein condensate, in the form of a two-dimensional axisymmetric Gaussian, shaped by means of the optical Feshbach resonance. The corresponding effective nonlinear trapping potential supports completely stable elongated QDs with vorticity \(S=0\) and partly stable families of elongated QDs with \(S=1,2,3,4\) (other nonlinear systems do not maintain stability of vortex droplets with \(\geq 2\)). We systematically analyze effects of the amplitude and width of the Gaussian modulation, as well as the total number of atoms, on the shape and stability of the QDs, some effects being explained analytically. Collisions between identical QDs with \(S=1\) moving in opposite directions along the central axis leads to their merger into still more elongated breathing QDs with the same vorticity, while collisions between QDs with \(S=\pm 1\) are quasi-elastic. Moving modulation profiles are able to adiabatically rotate the trapped elongated QDs. Application of a torque to the vector QD sets in the gyroscopic regime of robust precession, which realizes a macroscopic spin-orbit-coupling effect.
Quantum Gases (cond-mat.quant-gas)
7 pages, 90 References
Spontaneous magnon decay in two-dimensional altermagnets
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-28 20:00 EST
Niklas Cichutek, Peter Kopietz, Andreas Rückriegel
We show that magnons in two-dimensional altermagnets can spontaneously decay at zero temperature. The decay rate is determined by quantum fluctuations and scattering processes involving the decay of a single magnon into three. These processes are kinematically allowed due to the convexity of the altermagnetic magnon dispersion. For small wavevectors \(k\) the decay rate is proportional to \(k^5\) with a direction-dependent prefactor which is maximal along the diagonals of the Brillouin zone. Moreover, for a given momentum only magnons with one specific chirality can spontaneously decay.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
5 pages, 5 figures
Phonon anomalies within the polar charge density wave phase of superconductor Mo\(_3\)Al\(_2\)C with structural chirality
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-28 20:00 EST
Shangfei Wu, Xianghan Xu, Fei-Ting Huang, Turan Birol, Sang-Wook Cheong, Girsh Blumberg
We employ polarization-resolved Raman spectroscopy to study the lattice dynamics of the polar charge density wave phase of the superconductor Mo\(_3\)Al\(_2\)C with structural chirality. We show the phononic signatures of the charge density wave transition at \(T^\ast\)=155K in Mo\(_3\)Al\(_2\)C. The detailed temperature dependence of these phonon modes' frequency, half-width-at-half-maximum, and the integrated area below \(T^\ast\) reveal anomalies at an intermediate temperature $T'\(100K, especially for the low-energy modes at 130cm\)^{-1}$ and 180cm\(^{-1}\). Since these low-energy modes are dominated by Mo-related lattice vibration, we propose that lattice anomalies at \(T'\) within the charge density wave phase are related to a modification of the Mo displacements while preserving the crystal symmetry.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
9 pages, 6 figures. The supplemental materials are available upon request
Robust \(s_\pm\)-wave pairing in a bilayer two-orbital model of pressurized La\(_3\)Ni\(_2\)O\(_7\) without the \(γ\) Fermi surface
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-28 20:00 EST
We studied the superconducting pairing symmetry based on a newly constructed tight-binding model of La\(_3\)Ni\(_2\)O\(_7\) under pressure, where the \(\gamma\) band sinks below the Fermi level and does not form the Fermi surface. The superconducting pairing symmetry is \(s_\pm\)-wave and is robust against the variation of the interaction strength. In this model, although the \(\gamma\) and \(\delta\) bands are away from the Fermi level, the superconducting pairing function on them is not tiny. Instead, since the top of the \(\gamma\) band and bottom of the \(\delta\) band are both located at $$500 meV away from the Fermi level, and they are almost nested by the peak structure in the spin fluctuation, thus by forming an anti-phase pairing function on them, these two bands act constructively to superconductivity. Finally with detailed derivation and numerical calculation, we demonstrate that the Fermi surface approximated Eliashberg equation may lead to deviation of the pairing symmetry.
Superconductivity (cond-mat.supr-con)
arXiv admin note: text overlap with arXiv:2412.11429
Detecting Topological Phase Transition in Superconductor-Semiconductor Hybrids by Electronic Raman Spectroscopy
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-28 20:00 EST
Takeshi Mizushima, Yukio Tanaka, Jorge Cayao
In superconductor-semiconductor hybrids, applying a magnetic field closes a trivial bulk gap and causes a topological phase transition (TPT), resulting in the emergence of Majorana zero modes at both ends of the wires. However, trivial Andreev bound states formed at the interface with metallic leads mimic the local Majorana properties, making it difficult to detect the TPT through local conductance measurements. In this work, we investigate the detection of the bulk TPT by exploiting the static and dynamic density response of the hybrid system. In particular, we demonstrate that the dynamical renormalized responses reveal the characteristic electronic structure and detect the TPT, which we then show to produce strong intensities of Raman scattering. Furthermore, we find that gapless plasmons emerge in the normal state, signaling the bulk Lifshitz transition. Our results thus predict that the bulk response of superconducting nanowires is a powerful spectroscopic approach to detect the bulk topological phase transition.
Superconductivity (cond-mat.supr-con)
7 pages, 5 figures, and Supplemental Material
Dynamics of a Bottom-Heavy Janus Particle Near a Wall Under Shear Flow
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-28 20:00 EST
Zohreh Jalilvand, Daniele Notarmuzi, Ubaldo M. Córdova-Figueroa, Emanuela Bianchi, Ilona Kretzschmar
In this study, Brownian Dynamics simulations are implemented to investigate the motion of a bottom-heavy Janus particle near a wall under varying shear flow conditions and at small Péclet (Pe) numbers. The stochastic motion of the Janus particle impacted by surface forces is described using a set of coupled Langevin equations that takes into account the Janus particle orientation. Interactions arising from surface potentials are found to depend on the separation distance between the Janus particle and the wall, the properties of the surfaces involved, and the thickness of the Janus particle cap. When shear flow is introduced in the system, the dynamical behavior of the Janus particle is also governed by the strain rate. Furthermore, the effect of friction on the dynamical behavior of the Janus particle under shear flow is investigated and reveals that the rotational motion of the Janus particle slows down slightly when the particle is close to the surface. In summary, we demonstrate the ability to utilize Brownian Dynamics simulations to capture the rich dynamical behavior of a bottom-heavy Janus particle near a wall and under a range of shear flow conditions, cap thicknesses, and surface charges.
Soft Condensed Matter (cond-mat.soft)
Topological phase transitions in superconductors with chiral symmetry
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-28 20:00 EST
Kristian Løvås Svalland, Maria Teresa Mercaldo, Mario Cuoco
We study topological transitions in one dimensional superconductors that can harbor multiple edge Majorana bound states protected by chiral symmetry. The chiral symmetry arises due to the structure of the internal spin degrees of freedom of the superconductor and it can be guided by the coupling of the superconductor with sources of time-reversal symmetry breaking. We then consider distinct regions of the phase diagram in the parameters space that are marked by gapless excitations in the spectrum and evaluate the conditions for inducing a topological transition. We show that for gapless chiral symmetric superconductors one can identify a class of physical perturbations that enable a gap opening in the spectrum, without breaking chirality, and turn the system into a topological state. This type of superconductor is dubbed marginal topological superconductor because an infinitesimally small perturbation is able to induce a transition into a topological nontrivial phase. To explicitly demonstrate and evaluate the character of the transitions from gapless to topological gapfull phases we explore different physical cases including \(p\)-wave superconductor in the presence of an applied magnetic field or proximity-coupled to a ferromagnet, and \(s\)-wave superconductor in a noncollinear magnetic ordering.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
14 pages, 13 figures
Improvement of Morphology and Electrical Properties of Boron-doped Diamond Films via Seeding with HPHT Nanodiamonds Synthesized from 9-Borabicyclononane
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Stepan Stehlik, Stepan Potocky, Katerina Aubrechtova Dragounova, Petr Belsky, Rostislav Medlin, Andrej Vincze, Evgeny A. Ekimov, Alexander Kromka
Boron-doped diamond (BDD) films are becoming increasingly popular as electrode materials due to their broad potential window and stability in harsh conditions and environments. Therefore, optimizing the crystal quality and minimizing defect density to maximize electronic properties (e.g. conductivity) of BDD is of great importance. This study investigates the influence of different hydrogenated nanodiamond (H-ND) seeding layers on the growth and properties of BDD films. Three types of seeding H-NDs were examined: detonation (H-DND) and top-down high-pressure high-temperature NDs (TD_HPHT H-ND), and boron-doped NDs (H-BND) newly synthesized at high-pressure high-temperature from an organic precursor. Purified and oxidized BND (O-BND) samples yielded clear, blue, and stable colloidal dispersions. Subsequent thermal hydrogenation reversed their zeta potential from - 32 mV to + 44 mV and promoted the seeding of negatively charged surfaces. All three H-ND types formed dense seeding layers on SiO2 and Si/SiOx substrates, which enabled the growth of BDD films by chemical vapor deposition (CVD). Despite variations in initial surface coverage among the seeding layers (13-25%), all NDs facilitated the growth of fully closed BDD films approximately 1 {}m thick. Significant differences in film morphology and electrical properties were observed. H-BND nucleation yielded the BDD films with the largest crystals (up to 1 000 nm) and lowest sheet resistance (400 ohm/sq). This superior performance is attributed to the uniform particle shape and monocrystalline character of H-BND, as corroborated by FTIR, TEM, and SAXS measurements. These findings highlight the critical role of seeding layer properties in determining consequent diamond film evolution and establish H-BNDs as promising seeding material for the growth of high-quality BDD films suitable for electronic and electrochemical applications.
Materials Science (cond-mat.mtrl-sci)
Colossal Dielectric Response and Electric Polarization in Lithium Nitrate
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Na Du, Yan Zhao, Enting Xu, Jianwei Han, Peng Ren, Fei Yen
Materials with record-breaking properties are interesting as they can redefine existing models. Lithium nitrate LiNO\(_3\) is identified to possess a dielectric constant \(\epsilon\)' larger than 6x10\(^6\) at 1 kHz in powdered samples above the critical temperature \(T\)_W$ = 306 K. When cooling back from \(T\)_W$, if the temperature remains above 275 K, \(\epsilon\)' can be sustained above 10\(^4\) and the dissipation factor below 10\(^2\). Moreover, pyroelectric current measurements show LiNO\(_3\) to be ferroelectric with an electric polarization of \(P\) = 1,200 \(\mu\)C/cm\(^2\). Both \(\epsilon\)' and \(P\) are the highest amongst all known materials. We suggest the mechanism underlying the colossal magnitudes of \(\epsilon\)' and \(P\) to stem from a gearing-ungearing process of the planar NO\(_3\)^-$ at the macroscopic level. Our results potentially push the boundaries of ceramic capacitors.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph), Chemical Physics (physics.chem-ph)
13 pages, 5 figures, supplementary material available one paper is published
Effect of a uniaxial strain on optical spin orientation in cubic semiconductors
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-28 20:00 EST
The effect of a uniaxial strain on the optical spin orientation of a cubic semiconductor is investigated by calculating the valence wavefunctions, the optical oscillator strengths and the initial electron spin polarization for near resonant light excitation from heavy and light valence levels. A strain orientation along the [001], [111] or [-110] crystal direction and a circularly-polarized light excitation parallel or perpendicular to the strain are considered. For all these cases, the total conduction electron spin polarization has a universal character since i) the oscillator strengths do not depend on the magnitude of the strain but only on its sign. ii) Although the oscillator strengths strongly depend on the configuration, the conduction electron spin polarization generated by optical transitions from both the heavy and light valence levels induced by sigma + light excitation is in all cases equal to -0.5 as predicted by the simple atomic model. iii) The spin polarization generated by light excitation from heavy and light valence levels does not depend on the deformation tensor and on the valence deformation potential, except for a strain along [-110].
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Optical switching in a layered altermagnet
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-28 20:00 EST
Alessandro De Vita, Chiara Bigi, Davide Romanin, Matthew D. Watson, Vincent Polewczyk, Marta Zonno, François Bertran, My Bang Petersen, Federico Motti, Giovanni Vinai, Manuel Tuniz, Federico Cilento, Mario Cuoco, Brian M. Andersen, Andreas Kreisel, Luciano Jacopo D'Onofrio, Oliver J. Clark, Mark T. Edmonds, Christopher Candelora, Muxian Xu, Siyu Cheng, Alexander LaFleur, Tommaso Antonelli, Giorgio Sangiovanni, Lorenzo Del Re, Ivana Vobornik, Jun Fujii, Fabio Miletto Granozio, Alessia Sambri, Emiliano Di Gennaro, Jeppe B. Jacobsen, Henrik Jacobsen, Ralph Ernstorfer, Ilija Zeljkovic, Younghun Hwang, Matteo Calandra, Jill A. Miwa, Federico Mazzola
Altermagnetism defies conventional classifications of collinear magnetic phases, standing apart from ferromagnetism and antiferromagnetism with its unique combination of spin-dependent symmetries, net-zero magnetization, and anomalous Hall transport. Although altermagnetic states have been realized experimentally, their integration into functional devices has been hindered by the structural rigidity and poor tunability of existing materials. First, through cobalt intercalation of the superconducting 2H-NbSe\(_2\) polymorph, we induce and stabilize a robust altermagnetic phase and using both theory and experiment, we directly observe the lifting of Kramers degeneracy. Then, using ultrafast laser pulses, we demonstrate how the low temperature phase of this system can be quenched, realizing the first example of an optical altermagnetic switch. While shedding light on overlooked aspects of altermagnetism, our findings open pathways to spin-based technologies and lay a foundation for advancing the emerging field of altertronics.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Transmission through multiple Mott insulator - semiconductor wells
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-28 20:00 EST
Weakly and strongly interacting quantum many-body systems, namely semiconductors and Mott insulators, are combined into a layered heterostructure. Via the hierarchy of correlations, we derive and match the propagating quasi-particle solutions in the different regions and calculate the transmission coefficients through these layered structures. As a proof of principle, we find the well known transmission bands of a semiconductor heterostructure. Extending this idea to semiconductor and Mott insulator structures we calculate the transmittance and the resonance energies. Within a phase accumulation model we find analytical expressions for the scattering phase shift. Lastly, we find transmission curves with skewness for structures with applied voltage.
Strongly Correlated Electrons (cond-mat.str-el)
Computational Characterization of the Recently Synthesized Pristine and Porous 12-Atom-Wide Armchair Graphene Nanoribbon
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Djardiel da S. Gomes, Isaac M. Felix, Willian F. Radel, Alexandre C. Dias, Luiz A. Ribeiro Junior, Marcelo L. Pereira Junior
Recently synthesized Porous 12-Atom-Wide Armchair Graphene Nanoribbons Nano Lett. 2024, 24, 10718-10723 exhibit tunable properties through periodic porosity, enabling precise control over their electronic, optical, thermal, and mechanical behavior. This work presents a comprehensive theoretical characterization of pristine and porous 12-AGNRs based on density functional theory (DFT) and molecular dynamics (MD) simulations. DFT calculations reveal substantial electronic modifications, including band gap widening and the emergence of localized states. Analyzed within the Bethe-Salpeter equation (BSE) framework, optical properties highlight strong excitonic effects and significant absorption shifts. Thermal transport simulations indicate a pronounced reduction in conductivity due to enhanced phonon scattering at nanopores. At the same time, MD-based mechanical analysis shows decreased stiffness and strength while maintaining structural integrity. Despite these modifications, porous 12-AGNRs remain mechanically and thermally stable. These findings establish porosity engineering as a powerful strategy for tailoring graphene nanoribbons' functional properties, reinforcing their potential for nanoelectronic, optoelectronic, and thermal management applications.
Materials Science (cond-mat.mtrl-sci)
11 pages and 5 figures
Harnessing Layer-Controlled Two-dimensional Semiconductors for Photoelectrochemical Energy Storage via Quantum Capacitance and Band Nesting
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Praveen Kumar, Tushar Waghmare, Sudhir Kumar, Rajdeep Banerjee, Suman Kumar Chakraborty, Subrata Ghosh, Dipak Kumar Goswami, Sankha Mukherjee, Debabrata Pradhan, Prasana Kumar Sahoo
Two-dimensional (2D) transition metal dichalcogenides like molybdenum diselenide (MoSe\(_2\)) have shown great potential in optoelectronics and energy storage due to their layer-dependent bandgap. However, producing high-quality 2D MoSe\(_2\) layers in a scalable and controlled manner remains challenging. Traditional methods, such as hydrothermal and liquid-phase exfoliation, lack precision and understanding at the nanoscale, limiting further applications. Atmospheric pressure chemical vapor deposition (APCVD) offers a scalable solution for growing high-quality, large-area, layer-controlled 2D MoSe\(_2\). Despite this, the photoelectrochemical performance of APCVD-grown 2D MoSe\(_2\), particularly in energy storage, has not been extensively explored. This study addresses this by examining MoSe\(_2\)'s layer-dependent quantum capacitance and photo-induced charge storage properties. Using a three-electrode setup in 0.5M H\(_2\)SO\(_4\), we observed a layer-dependent increase in areal capacitance under both dark and illuminated conditions. A six-layer MoSe\(_2\) film exhibited the highest capacitance, reaching \(96 \mu\mathrm{F/cm^2}\) in the dark and \(115 \mu\mathrm{F/cm^2}\) under illumination at a current density of \(5 \mu\mathrm{A/cm^2}\). Density Functional Theory (DFT) and Many-Body Perturbation Theory calculations reveal that Van Hove singularities and band nesting significantly enhance optical absorption and quantum capacitance. These results highlight APCVD-grown 2D MoSe\(_2\)'s potential as light-responsive, high-performance energy storage electrodes, paving the way for innovative energy storage systems.
Materials Science (cond-mat.mtrl-sci)
28 pages, 6 figures (Main Manuscript) 8 figures (Supporting Information)
Simulating Bulk Gap in Chiral Projected Entangled-Pair States
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-28 20:00 EST
Ji-Yao Chen, Yi Tan, Sylvain Capponi, Didier Poilblanc, Fei Ye, Jia-Wei Mei
Projected entangled-pair states (PEPS) have proven effective in
capturing chiral spin liquid ground states, yet the presence of
long-range
gossamer'' correlation tails raises concerns about their ability to accurately describe bulk gaps. Here, we address this challenge and demonstrate that PEPS can reliably characterize gapped bulk excitations in chiral topological phases. Using a variational principle for excited states within a local mode approximation, we establish that correlation functions decaying faster than $r^{-2}$ are not necessarily related to gapless modes and thus long-rangegossamer''
correlation tails in chiral PEPS do not contradict the presence of a
bulk gap. This framework is validated in the spin-\(\frac{1}{2}\) Kitaev model with a chiral
term, where PEPS yields excitation gaps that agree well with exact
solutions. Extending our approach to the \(\mathbb{Z}_3\) Kitaev model, we present
compelling evidence for its chiral ground state and accurately resolve
its gapped excitations. These findings thus solidify PEPS as a powerful
tool for studying both ground and excited states in chiral topological
systems, thereby bridging a key gap in the understanding of their bulk
properties.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
4 figures in 6 pages
Spontaneous Magnon Decays from Nonrelativistic Time-Reversal Symmetry Breaking in Altermagnets
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-02-28 20:00 EST
Rintaro Eto, Matthias Gohlke, Jairo Sinova, Masahito Mochizuki, Alexander L. Chernyshev, Alexander Mook
Quasiparticles are central to condensed matter physics, but their stability can be undermined by quantum many-body interactions. Magnons, quasiparticles in quantum magnets, are particularly intriguing because their properties are governed by both real and spin space. While crystal symmetries may be low, spin interactions often remain approximately isotropic, limiting spontaneous magnon decay. Textbook wisdom holds that collinear Heisenberg magnets follow a dichotomy: ferromagnets host stable magnons, while antiferromagnetic magnons may decay depending on dispersion curvature. Up to now, relativistic spin-orbit coupling and noncollinear order that connect spin space to real space, were shown to introduce more complex magnon instability mechanisms. Here, we show that even in nonrelativistic isotropic collinear systems, this conventional dichotomy is disrupted in altermagnets. Altermagnets, a newly identified class of collinear magnets, exhibit compensated spin order with nonrelativistic time-reversal symmetry breaking and even-parity band splitting. Using kinematic analysis, nonlinear spin-wave theory, and quantum simulations, we reveal that even weak band splitting opens a decay phase space, driving quasiparticle breakdown. Additionally, d-wave altermagnets form a rare ``island of stability'' at the Brillouin zone center. Our findings establish a quasiparticle stability trichotomy in collinear Heisenberg magnets and position altermagnets as a promising platform for unconventional spin dynamics.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
14 pages
Geometry and Mechanics of Non-Euclidean Curved-Crease Origami
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-28 20:00 EST
Zhixuan Wen, Tian Yu, Fan Feng
Recently there have been extensive theoretical, numerical and experimental works on curved-fold origami. However, we notice that a unified and complete geometric framework for describing the geometry and mechanics of curved-fold origami, especially those with nontrivial Gaussian curvature at the crease (non-Euclidean crease), is still absent. Herein we provide a unified geometric framework that describes the shape of a generic curved-fold origami composed of two general strips. The explicit description indicates that four configurations emerge, determined by its spatial crease and configuration branch. Within this geometric framework, we derive the equilibrium equations and study the mechanical response of the curved-crease origami, focusing on Euler's buckling behavior. Both linear stability analysis and finite element simulation indicate that the overlaid configuration exhibits a lower buckling threshold. To further capture the large deformation behavior efficiently, we develop a bistrip model based on the anisotropic Kirchhoff rod theory, which predicts the main features successfully. This work bridges the geometry and mechanics of curved-crease origami, offering insights for applications in robotics, actuators, and deployable space structures.
Soft Condensed Matter (cond-mat.soft)
22 pages
Strong-damping limit of quantum Brownian motion in a disordered environment
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-28 20:00 EST
Arthur M. Faria, Marcus V. S. Bonanca, Eric Lutz
We consider a microscopic model of an inhomogeneous environment where an arbitrary quantum system is locally coupled to a harmonic bath via a finite-range interaction. We show that in the overdamped regime the position distribution obeys a classical Kramers-Moyal equation that involves an infinite number of higher derivatives, implying that the finite bath correlation length leads to non-Gaussian Markovian noise. We analytically solve the equation for a harmonically bound particle and analyze its non-Gaussian diffusion as well as its steady-state properties.
Statistical Mechanics (cond-mat.stat-mech)
7 pages, 3 figures
Nonequilibrium fluctuation relations for non-Gaussian processes
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-02-28 20:00 EST
Arthur M. Faria, Marcus V. S. Bonanca, Eric Lutz
Non-Gaussian noise is omnipresent in systems where the central-limit theorem is inapplicable. We here investigate the stochastic thermodynamics of small systems that are described by a general Kramers-Moyal equation that includes both Gaussian and non-Gaussian white noise contributions. We obtain detailed and integral fluctuation relations for the nonequilibrium entropy production of these Markov processes in the regime of weak noise. As an application, we analyze the properties of driven objects that are locally coupled to a heat bath via a finite-range interaction, by considering an overdamped particle that is pulled by a moving harmonic potential. We find that reducing the bath interaction range increases non-Gaussian features, and strongly suppresses the average nonequilibrium entropy production. We further discuss a generalized detailed-balance condition.
Statistical Mechanics (cond-mat.stat-mech)
12 pages, 4 figures
Homogeneous doping of epitaxial graphene by Pb(111) islands: A magnetotransport study
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-28 20:00 EST
Julian Koch, Sergii Sologub, Dorothee Sylvia Boesler, Chitran Ghosal, Teresa Tschirner, Klaus Pierz, Hans Werner Schumacher, Christoph Tegenkamp
Proximity coupling is an effective approach for the functionalization of graphene. However, graphene's inertness inhibits the adsorption of closed films, thus favoring island growth, whose inhomogeneity might be reflected in the induced properties. In order to study the homogeneity of the doping profile induced by an inhomogeneous coverage and the spin orbit coupling (SOC) induced in graphene, we deposited Pb(111) islands with an average coverage of up to 30 ML on monolayer graphene (MLG) on SiC(0001) at room temperature (RT). We investigated the transport properties and the structure using magnetotransport, and scanning tunneling microscopy and low energy electron deflection, respectively. The Pb(111) islands act as donors, increasing the electron concentration of graphene by about \(5\times10^{11}\;\text{ML}^{-1}\text{cm}^{-2}\). The doping was found to be homogeneous, in stark contrast to our previous results for Bi islands on MLG. Upon percolation of the Pb layer at around 5 ML, hole transport through the Pb islands has to be taken into account in order to describe the transport data. The Pb(111) islands do not induce any Rashba SOC, contrary to theoretical predictions for an interface between Pb(111) and graphene. Moreover, they seem to screen the defects in the graphene, resulting in a reduction of the intervalley scattering rate up to 5 ML.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
8 pages, 8 figures
Processing-dependent Chemical Ordering in a Metallic Alloy Characterized via Non-destructive Bragg Coherent Diffraction Imaging
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Nathaniel Warren, Chloe Skidmore, Katherine J. Harmon, Wonsuk Cha, Jon-Paul Maria, Stephan O. Hruszkewycz, Darren C. Pagan
Of current importance for alloy design is controlling chemical ordering through processing routes to optimize an alloy's mechanical properties for a desired application. However, characterization of chemical ordering remains an ongoing challenge, particularly when nondestructive characterization is needed. In this study, Bragg coherent diffraction imaging is used to reconstruct morphology and lattice displacement in model Cu\(_3\)Au nanocrystals that have undergone different heat treatments to produce variation in chemical ordering. The magnitudes and distributions of the scattering amplitudes (proportional to electron density) and lattice strains within these crystals are then analyzed to correlate them to the expected amount of chemical ordering present. Nanocrystals with increased amounts of ordering are found to generally have less extreme strains present and reduced strain distribution widths. In addition, statistical correlations are found between the spatial arrangement of scattering amplitude and lattice strains.
Materials Science (cond-mat.mtrl-sci)
Environment-friendly technologies with lead-free piezoelectric materials: A review of recent developments, applications, and modelling approaches
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Akshayveer Akshayveer, Federico C Buroni, Roderick Melnik, Luis Rodriguez-Tembleque, Andres Saez
Piezoelectric materials are widely used in several industries, including power sources, energy harvesting, biomedical, electronics, haptic, photostrictive, and sensor/actuator technologies. Conventional piezoelectric materials, such lead zirconate titanate (PZT), pose significant environmental and health risks due to lead content. Recent years have seen a growing need for eco-friendly alternatives to lead-based piezoelectric technologies. The drawback of lead-free piezoelectric materials is a reduced responsiveness. To enhance the performance of lead-free piezoelectric materials, substantial research is being undertaken using both experimental and numerical methods. The experimental studies provide a deep understanding of the process and are crucial for developing lead-free piezoelectric materials. Relying only on experimental research is not feasible due to high expenditures. To understand the piezoelectric properties of lead-free materials and enhance their efficiency, it is crucial to develop varied numerical models and computational methods. This paper is a comprehensive summary of lead-free piezoelectric technology breakthroughs. The study emphasizes numerical models that demonstrate enhanced piezoelectric behaviour and their use in eco-friendly technologies like energy harvesting, haptics, nano-electromechanical, photostrictive, and biomedical sensors and actuators using lead-free materials. The paper discusses the synthesis, properties, and applications of eco-friendly materials, highlighting their potential to revolutionize piezoelectric devices and promote sustainable development and conservation.
Materials Science (cond-mat.mtrl-sci), Mathematical Physics (math-ph)
48 pages, 3 figures
Carrier Localization and Spontaneous Formation of Two-Dimensional Polarization Domain in Halide Perovskites
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-02-28 20:00 EST
Andrew Grieder, Marcos Calegari Andrade, Hiroyuki Takenaka, Tadashi Ogitsu, Liang Z. Tan, Yuan Ping
Halide perovskites are known for their rich phase diagram and superior performance in diverse optoelectronics applications. The latter property is often attributed to the long electron-hole recombination time, whose underlying physical mechanism has been a long-standing controversy. In this work, we investigate the transport and localization properties of electron and hole carriers in a prototypical halide perovskite (CsPbBr3), through ab initio tight-binding non-adiabatic dynamics approach for large-scale (tens of nm size) supercell calculations. We found distinct structural, lattice polarization, and electron-phonon coupling properties at low (below 100 K) and high temperatures, consistent with experimental observations. In particular, at low temperature we find spontaneous formation of polar grain-boundaries in the nonpolar bulk systems, which result in two dimensional polarization patterns that serve to localize and separate electrons and holes. We reveal phonon-assisted variable-range hopping mostly responsible for low-temperature transport, and their characteristic frequency correlates with temperature-dependent phonon power spectrum and energy oscillation frequency in nonadiabatic dynamics. We answer the critical questions of long electron-hole recombination lifetime and offer the correlation among polarization domains, electron-phonon couplings, and photocarrier dynamics.
Materials Science (cond-mat.mtrl-sci)
Chaotic quantum transport through spatially symmetric microstructures in the symplectic ensemble
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-28 20:00 EST
Felipe Castañeda-Ramírez, Moisés Martínez-Mares
Quantum transport through left-right symmetric chaotic cavities in the presence of the symplectic symmetry, is studied through the statistical distribution of the dimensionless conductance. With this particular point symmetry, their associated scattering matrices are blocky diagonalized by a rotation by an angle of \(\pi/4\). Although the formulation is established for an arbitrary number channels N, we present explicit calculations for N=1 and N=2, the last one showing the weak anti-localization phenomenon due to the symplectic symmetry.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Submitted to Academia Quantum
Search for magnetic field expulsion in optically driven K\(_3\)C\(_{60}\)
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-28 20:00 EST
G. De Vecchi, M. Buzzi, G. Jotzu, S. Fava, T. Gebert, G. Magnani, D. Pontiroli, M. Riccò, A. Cavalleri
Photoexcited K\(_3\)C\(_{60}\) displays several properties reminiscent of equilibrium superconductivity, including transient optical spectra, pressure dependence, and I-V characteristics. However, these observations do not decisively establish non-equilibrium superconductivity, which would be conclusively evidenced by transient Meissner diamagnetism, as shown recently in driven YBa\(_2\)Cu\(_3\)O\(_{6.48}\). Here, we search for transient magnetic field expulsion in K\(_3\)C\(_{60}\) by measuring Faraday rotation in a magneto-optic material placed in its vicinity. Unlike in the case of homogeneous, insulating YBa\(_2\)Cu\(_3\)O\(_{6.48}\), inhomogeneous, metallic K\(_3\)C\(_{60}\) powders reduce the size of the effect. With the \(\sim50\) nT magnetic field resolution achieved in our experiments, we provide an upper limit for the photo-induced diamagnetic volume susceptibility (\(\chi_v>-0.1\)). On this basis, we conclude that the photo-induced phase has weaker diamagnetism than superconducting K\(_3\)C\(_{60}\) at zero temperature. Yet, from recent nonlinear transport measurements in this granular material, we expect a light-induced state similar to the equilibrium superconductor near 0.8 T\(_c\), for which \(\chi_v>-0.1\). A definitive conclusion on the presence or absence of Meissner diamagnetism cannot be made for K\(_3\)C\(_{60}\) with the current resolution.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
3 figures, 42 pages, including supplementary information. arXiv admin note: text overlap with arXiv:2408.05153
Topological altermagnetic Josephson junctions
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-28 20:00 EST
Grant Z. X. Yang, Zi-Ting Sun, Ying-Ming Xie, K. T. Law
Planar Josephson junctions are pivotal for engineering topological superconductivity, yet are severely hindered by orbital effects induced by in-plane magnetic fields. In this work, we introduce the generic topological altermagnetic Josephson junctions (TAJJs) by leveraging the intrinsic spin-polarized band splitting and zero net magnetization attributes of altermagnets. Our proposed TAJJs effectively mitigate the detrimental orbital effects while robustly hosting Majorana end modes (MEMs) at both ends of the junction. Specifically, we demonstrate that MEMs emerge in \(d_{x^2-y^2}\)-wave TAJJs but vanish in the \(d_{xy}\)-wave configuration, thereby establishing the crystallographic orientation angle \(\theta\) of the altermagnet as a novel control parameter of topology. The distinct spin-polarization of the MEMs provides an unambiguous experimental signature for the spin-resolved measurement. Furthermore, by harnessing the synergy between the \(d_{x^2-y^2}\)-wave altermagnet and its superconducting counterpart, our proposal extends to high-\(T_c\) platforms naturally. Overall, this work establishes altermagnets as a versatile paradigm for realizing topological superconductivity, bridging conceptual innovations with scalable quantum architectures devoid of orbital effects and stray fields.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 4 figures
Silver(I) complexes with nitrile ligands: new materials with versatile applications
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-02-28 20:00 EST
Karolina Gutmańska, Piotr Szweda, Marek Daszkiewicz, Konrad Szaciłowski, Tomasz Mazur, Anna Ciborska, Anna Dołęga
In the present study, the structure, thermal stability, conductive properties, and antimicrobial activity of silver(I) complexes with nitrile ligands were investigated. For the construction of the materials, 2 cyanopyridine (2-cpy), 4-cyanopyridine (4-cpy), 1,2-dicyanobenzene (1,2-dcb), and 1,3 dicyanobenzene (1,3-dcb) were used in addition to the silver nitrite and nitrate. Four new compounds were isolated and structurally characterized: one molecular complex [Ag4(1,2-dcb)4(NO3)4], two 1-D coordination polymers [Ag2(2-cpy)2(NO2)2], [Ag3(1,3-dcb)2(NO3)2] and one 3-D coordination polymer [Ag(4-cpy)(NO2)]. The results indicate that the nitrite complexes display good antimicrobial properties against the tested bacterial and fungal strains. The presence of weakly coordinating CN groups increases the release of silver ions into the bacterial and yeast cell environments. Moreover, these materials exhibit unusual electrical properties in thin-layer devices. On the other hand, the nitrite and nitrate counterions give rise to the low thermal stability of the complexes.
Soft Condensed Matter (cond-mat.soft)
Appl Organomet Chem. 2023;37:e7207
Half-Metallic Fe/MgO Superlattice: An Ideal Candidate for Magnetic Tunnel Junction Electrodes
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-02-28 20:00 EST
Nicholas A. Lanzillo, Sergey Faleev, Aakash Pushp
Magnetic Tunnel Junction (MTJ) based Spin-Transfer Torque Magnetic Random Access Memory (STT-MRAM) is poised to replace embedded Flash for advanced applications such as automotive microcontroller units. To achieve deeper technological adoption, MTJ needs to exhibit three key features: low magnetization (Ms), high perpendicular magnetic anisotropy (PMA) and high tunnel magnetoresistance (TMR). Here, we theoretically show that when Fe/MgO multilayers are inserted into the fixed and free layers of the MTJ, these three conditions are simultaneously met. As the number of Fe/MgO multilayers in MTJ electrodes is increased, we find that the electron transport evolves from direct barrier tunneling of majority spin states to the resonant tunneling of minority spin states. Remarkably, the projected density of states (PDOS) of Fe/MgO superlattice at the MgO tunnel barrier exhibits half-metallicity near the Fermi Energy, where the minority states exist while the majority states are gapped out, resulting in astronomically high TMR.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other), Applied Physics (physics.app-ph), Computational Physics (physics.comp-ph)
Superconductivity in doped planar Dirac insulators: A renormalization group study
New Submission | Superconductivity (cond-mat.supr-con) | 2025-02-28 20:00 EST
Sk Asrap Murshed, Sanjib Kumar Das, Bitan Roy
From a leading-order unbiased renormalization group analysis we here showcase the emergence of superconductivity (including the topological ones) from purely repulsive electron-electron interactions in two-dimensional doped Dirac insulators, featuring a Fermi surface. In the absence of chemical doping, such systems describe quantum anomalous or spin Hall and normal insulators. Otherwise a simply connected Fermi surface becomes annular deep inside the topological regime. By considering all symmetry allowed repulsive local four-fermion interactions, we show that the nature of the resulting superconducting states at low temperature follows certain Clifford algebraic selection rules, irrespective of the underlying Fermi surface topology. Within the framework of a microscopic Hubbard model, on-site repulsion among fermions with opposite orbitals (spin projections) typically favors topological \(p\)-wave (conventional \(s\)-wave) pairing. Theoretically predicted superconductivity can in principle be observed in experiments once the promising candidate materials for quantum anomalous and spin Hall insulators are doped to foster Fermi surfaces.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Theory (hep-th)
21 Pages, 9 Figures, and 4 Tables