CMP Journal 2025-04-07
Statistics
Nature Physics: 2
arXiv: 45
Nature Physics
Observation of polarization density waves in SrTiO3
Original Paper | Ferroelectrics and multiferroics | 2025-04-06 20:00 EDT
Gal Orenstein, Viktor Krapivin, Yijing Huang, Zhuquan Zhang, Gilberto de la Peña Muñoz, Ryan A. Duncan, Quynh Nguyen, Jade Stanton, Samuel Teitelbaum, Hasan Yavas, Takahiro Sato, Matthias C. Hoffmann, Patrick Kramer, Jiahao Zhang, Andrea Cavalleri, Riccardo Comin, Mark P. M. Dean, Ankit S. Disa, Michael Först, Steven L. Johnson, Matteo Mitrano, Andrew M. Rappe, David Reis, Diling Zhu, Keith A. Nelson, Mariano Trigo
The nature of the incipient ferroelectric transition in SrTiO3 has been a long-standing puzzle in condensed matter physics. One explanation involves the competition between ferroelectricity and an instability characterized by the mesoscopic modulation of the polarization. These polarization density waves, which should intensify near the quantum critical point, break local inversion symmetry and are difficult to characterize with conventional X-ray scattering methods. Here we probe inversion symmetry breaking at finite momenta and visualize the instability of the polarization at the nanometre scale in SrTiO3 by combining a femtosecond X-ray free-electron laser with terahertz coherent control methods. We found polar-acoustic collective modes that are soft, particularly at the tens of nanometre scale. These precursor collective excitations provide evidence for the conjectured mesoscopic-modulated phase in SrTiO3.
Ferroelectrics and multiferroics, Phase transitions and critical phenomena, Ultrafast photonics, X-rays
The strongly driven Fermi polaron
Original Paper | Atomic and molecular interactions with photons | 2025-04-06 20:00 EDT
Franklin J. Vivanco, Alexander Schuckert, Songtao Huang, Grant L. Schumacher, Gabriel G. T. Assumpção, Yunpeng Ji, Jianyi Chen, Michael Knap, Nir Navon
Quasiparticles are emergent excitations of matter that underlie much of our understanding of quantum many-body systems. Therefore, the prospect of controlling their properties has both fundamental and practical implications. However, in solid-state materials, it is often challenging to understand how quasiparticles are modified by external fields due to their complex interplay with other collective excitations. Here we demonstrate the manipulation of Fermi polarons–quasiparticles formed by impurities interacting with a Fermi gas–in a homogeneous atomic gas using fast radio-frequency control. Exploiting two internal states of the impurity species, we develop a steady-state spectroscopy, from which we extract the energy of the driven polaron. By varying the drive Rabi frequency, we measure the decay rate and the quasiparticle residue of the polaron in the weak-drive limit. At large Rabi frequencies, we observe signs that the drive causes a hybridization of the driven polaron with an incoherent background, leading to the breakdown of a description in terms of textbook quasiparticles. Our experiment establishes the driven Fermi polaron as a promising platform for studying controllable quasiparticles in strongly driven quantum matter and calls for a controlled theoretical framework to describe the dynamics of this strongly interacting quantum system.
Atomic and molecular interactions with photons, Quantum simulation, Ultracold gases
arXiv
Bootstrapping the Electronic Structure of Quantum Materials
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-07 20:00 EDT
Anna O. Schouten, Simon Ewing, David A. Mazziotti
The last several decades have seen significant advances in the theoretical modeling of materials within the fields of solid-state physics and materials science, but many methods commonly applied to this problem struggle to capture strong electron correlation accurately. Recent widespread interest in quantum materials – where strong correlation plays a crucial role in the quantum effects governing their behavior – further highlights the need for theoretical methods capable of rigorously treating such correlation. Here, we present a periodic generalization of variational two-electron reduced density matrix (2-RDM) theory, a bootstrapping-type method that minimizes the ground-state energy as a functional of the 2-RDM without relying on the wavefunction. The 2-RDM is computed directly by semidefinite programming with $ N$ -representability conditions, ensuring accurate treatment of strongly correlated electronic systems. By exploiting translational symmetry, we significantly reduce computational scaling, enabling applications to realistic materials-scale systems. Additionally, we introduce an alternative to conventional energy band structures: natural-orbital occupation-number bands, which, being independent of mean-field assumptions, offer deeper insights into electron correlation effects. We demonstrate the effectiveness of this approach by applying the theory to hydrogen chains, molybdenum disulfide, and nickel oxide, showing that natural-orbital occupation bands correctly capture electronic character in regimes where density functional theory fails. This work represents a major step toward accurately describing the electronic structure of quantum materials using reduced density matrices rather than wavefunctions.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph), Quantum Physics (quant-ph)
Excitonic and magnetic phases in doped WTe$_2$ monolayers: a Hartree-Fock approach
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-07 20:00 EDT
Guillermo Parra-Martínez, Daniel Muñoz-Segovia, Héctor Ochoa, Jose Angel Silva-Guillén
Transport and local spectroscopy measurements have revealed that monolayers of tungsten ditelluride ($ 1T’$ -WTe$ _2$ ) display a quantum spin Hall effect and an excitonic gap at neutrality, besides becoming superconducting at low electron concentrations. With the aim of studying the competition among different broken-symmetry phases upon electron doping, we have performed extensive Hartree-Fock calculations as a function of electron density and Coulomb interaction strength. At charge neutrality, we reproduce the emergence of a spin density wave and a spin spiral state surrounding a quantum spin Hall insulator at intermediate interaction strengths. For stronger interactions, the spin spiral is disrupted by a state breaking both inversion and time-reversal symmetries (but not their product) before the system becomes a trivial band insulator. With electron doping the quantum spin Hall insulator evolves into an easy-plane ferromagnet due to a Stoner-like instability of the conduction band. This phase competes energetically with the spin spiral state. We discuss how our results may help to interpret past and future measurements.
Strongly Correlated Electrons (cond-mat.str-el)
11 pages, 8 figures
Perfect supercurrent diode efficiency in chiral nanotube-based Josephson junctions
New Submission | Superconductivity (cond-mat.supr-con) | 2025-04-07 20:00 EDT
Joseph J. Cuozzo, François Léonard
The supercurrent diode effect (SDE) describes superconducting systems where the magnitude of the superconducting-to-normal state switching current differs for positive and negative current bias. Despite the ubiquity of such diode effects in Josephson devices, the fundamental conditions to observe a diode effect in a Josephson junction and achieve perfect diode efficiency remain unclear. In this work, we analyze the supercurrent diode properties of a chiral nanotube-based Josephson junction within a Ginzburg-Landau theory. We find a diode effect and anomalous phase develops across the junction when a magnetic field is applied parallel to the tube despite the absence of spin-orbit interactions in the system. Unexpectedly, the SDE in the junction is independent of the anomalous phase. Alternatively, we determine a non-reciprocal persistent current that is protected by fluxoid quantization can activate SDE, even in the absence of higher-order pair tunneling processes. We show this new type of SDE can lead to, in principle, a perfect diode efficiency, highlighting how persistent currents can be used to engineer high efficiency supercurrent diodes.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 2 figures
Quantum shockwave at the quasi-relativistic resonance
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-07 20:00 EDT
We analyze the electromagnetic field travelling on resonance with the limiting velocity of the quasi-relativistic particle. We show that a strong longitudinal field leads to the quantum wave function singularity in the form of a shockwave, accompanied by strong energy dissipation. We show that the effect is particularly strong in the case of Dirac electrons in graphene due to the small effective mass. We discuss several experimental tests of these predictions.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Composite Bosons Superposition Ansatz Approach to One-Dimensional Trapped Few-Fermion Systems
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-04-07 20:00 EDT
Francisco Figueiredo, Itzhak Roditi
Ultra-cold atomic systems provide a versatile platform for exploring quantum phenomena, offering tunable interactions and diverse trapping geometries. In this study, we investigate a one-dimensional system of trapped fermionic atoms using the composite boson formalism, which describes pairs of opposite-spin fermions as cobosons (short for composite bosons). By constructing a superposition ansatz of coboson states, we solve the Schrödinger equation for two fermion pairs under both attractive and repulsive interactions. We determine key observables such as particle density profiles and two-body correlations. Additionally, we compute the low-lying energy spectrum and estimate the pairing gap. Our results highlight the potential of the coboson formalism for exploring quantum phenomena in strongly correlated few-body systems, achieving results comparable to standard exact diagonalization techniques.
Quantum Gases (cond-mat.quant-gas), Strongly Correlated Electrons (cond-mat.str-el)
13 pages, 6 figures
Noise-Affected Dynamical Quantum Phase Transitions
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-07 20:00 EDT
R. Jafari, Alireza Akbari, Mehdi Biderang, Jesko Sirker
We investigate the effects of uncorrelated noise on dynamical quantum phase transitions (DQPTs) following a quantum ramp across critical points in two different scenarios. First, we show that for a slow ramp in the XY model caused by a stochastically driven field an intriguing and counterintuitive phenomenon arises where the Loschmidt amplitude vanishes in an entire critical region in time. At the boundaries of such a region, DQPTs in the return rate with diverging slopes appear in contrast to the regular DQPTs with finite slopes for a ramp without noise. We also show that the critical ramp velocity beyond which DQPTs disappear entirely, as well as the critical ramp velocity separating the regime with critical regions in time from the regime with standard DQPTs, are both described by universal scaling functions. Second, we study the impact of the environment on DQPTs based on the Kubo-Anderson spectral diffusion process, where the environmental effects on the system are simulated as stochastic fluctuations in the energy levels of the post-ramp Hamiltonian. In this framework, the noise master equation can be solved analytically both for uncorrelated and correlated noise. The obtained analytical expression for the return rate reveals that DQPTs in this case are always completely eliminated.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
Selective colloid transport across planar polymer brushes
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-07 20:00 EDT
Mikhail Y. Laktionov (1), Ekaterina B. Zhulina (1,2), Leonid Klushin (2,3), Ralf P. Richter (4), Oleg V. Borisov (1,2,5) ((1) <a href=”http://St.Petersburg“ rel=”external noopener nofollow” class=”link-external link-http”>this http URL</a> National Research University of Information Technologies Mechanics and Optics, (2) Institute of Macromolecular Compounds Russian Academy of Sciences, (3) Department of Physics American University of Beirut, (4) School of Biomedical Sciences University of Leeds, (5) CNRS Université de Pau et des Pays de l’Adour UMR 5254 Institut des Sciences Analytiques et de Physico-Chimie pour l’Environnement et les Matériaux)
Polymer brushes are attractive as surface coatings for a wide range of applications, from fundamental research to everyday life, and also play important roles in biological systems. How colloids (e.g., functional nanoparticles, proteins, viruses) bind and move across polymer brushes is an important yet under-studied problem. We present a mean-field theoretical approach to analyze the binding and transport of colloids in planar polymer brushes. The theory explicitly considers the effect of solvent strength on brush conformation and of colloid-polymer affinity on colloid binding and transport. We derive the position-dependent free energy of the colloid insertion into the polymer brush which controls the rate of colloid transport across the brush. We show how the properties of the brush can be adjusted for brushes to be highly selective, effectively serving as tuneable gates with respect to colloid size and affinity to the brush-forming polymer. The most important parameter regime simultaneously allowing for high brush permeability and selectivity corresponds to a condition when the repulsive and attractive contributions to the colloid insertion free energy nearly cancel. Our theory should be useful to design sensing and purification devices with enhanced selectivity and to better understand mechanisms underpinning the functions of biopolymer brushes.
Soft Condensed Matter (cond-mat.soft)
33 pages, 11 figures in the main text, 1 table of content figure, 1 figure in the supporting information. Published in Macromol. Rapid Commun. with open access
Macromol. Rapid Commun. 2023, 44, 2200980
Theory of polyelectrolyte dendrigrafts
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-07 20:00 EDT
Oleg V. Borisov (1), Oleg V. Shavykin (1,2), Ekaterina B. Zhulina (2) ((1) CNRS Institut des Sciences Analytiques et de Physico-Chimie pour l’Environnement et les Matériaux Université de Pau et des Pays de l’Adour, (2) Institute of Macromolecular Compounds of the Russian Academy of Sciences)
A mean-field approach is used to analyze equilibrium conformations of polyelectrolyte dendrigrafts comprising ionically charged dendrons attached by focal points to a flexible linear backbone. Power law dependences for local structural parameters, cross-sectional thickness and intergraft distance, are derived as a function of grafting density and degree of branching of the dendrons. The cases of quenched and pH-sensitive ionization of the dendrons are considered. The finite extensibility of the backbone is taken into account. It is demonstrated that an increase in the degree of branching of the dendrons leads to a decrease in the dendrigraft thickness compared with that of the polyelectrolyte molecular brush with the same degree of polymerization of the side chains, while intergraft distance either increases or stays close to counter length of fully extended backbone spacer. The analytical mean-field theory predictions are confirmed by results of numerical self-consistent field modelling.
Soft Condensed Matter (cond-mat.soft)
20 pages, 4 figures, published in Colloid Polym Sci
Colloid Polym Sci 298, 951-959 (2020)
Micelle Formation of Diblock Copolymers Driven by Cononsolvency Effect
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-07 20:00 EDT
Xiangyu Zhang, Jing Zong, Dong Meng
This study utilizes self-consistent field theory to characterize various features of cononsolvency-driven spherical micelles formed by double hydrophilic block copolymers (DHBCs). Micelles are observed only at an intermediate cosolvent fraction, forming abruptly at a specific solvent/cosolvent mixing ratio and gradually disappearing with further cosolvent addition. A stronger core-block - cosolvent attractive interaction leads to a lower critical micelle concentration and a higher aggregation number. The density profile of cononsolvency-driven micelles is compared with that of conventional micelles, which form due to core-block - solvent repulsive interactions. In conventional micelles, the core is primarily occupied by polymer segments, whereas in cononsolvency-driven micelles, the core consists mainly of solvents and cosolvents. This fundamental difference can be explained through thermodynamic analysis. Conventional micelle formation is driven by the reduction of core-block - solvent contact due to repulsive interactions. In contrast, cononsolvency-driven micelle formation is governed by an increase in core-block - cosolvent contact area, playing the major role to minimize the total free energy-an essential distinction from conventional micelles.
Soft Condensed Matter (cond-mat.soft)
Formation of multiple quantum dots in ZnO heterostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-07 20:00 EDT
Koichi Baba, Kosuke Noro, Yusuke Kozuka, Takeshi Kumasaka, Motoya Shinozaki, Masashi Kawasaki, Tomohiro Otsuka
In recent years, advancements in semiconductor manufacturing technology have enabled the formation of high-quality, high-mobility two-dimensional electron gases in zinc oxide (ZnO) heterostructures, making the electrostatic formation of quantum dots possible. ZnO, with its low natural abundance of isotopes possessing nuclear spin and its direct bandgap, is considered a potentially suitable material for quantum bit applications. In this study, we achieve the formation of triple quantum dots and the realization of a few-electron state in ZnO heterostructure devices. We also confirm that by varying the gate voltage between the quantum dots, it is possible to control the interdot spacing. Additionally, we observe a tunneling phenomenon called a quantum cellular automata effect, where multiple electrons move simultaneously, which is not seen in single or double quantum dots, due to Coulomb interactions. Our results demonstrate that ZnO nanostructures have reached a level where they can function as controllable multiple quantum dot systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
15 pages, 4 figures
Thermodynamic Properties and Magnetocaloric Effect in a Rotating 2DEG under the Sagnac Effect
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-07 20:00 EDT
Cleverson Filgueiras, Moises Rojas, Vinicius T. Pieve, Edilberto O. Silva
This work investigates the impact of the Sagnac effect on the thermodynamic properties of a non-interacting two-dimensional electron gas (2DEG) in a rotating sample under the influence of a uniform magnetic field. We analyze how rotation and the distinction between effective mass ($ m^\ast$ ) and gravitational mass ($ m_G$ ) affect the energy levels and resulting thermodynamic properties. The results show that rotation modifies the energy levels, the application of a magnetic field leads to the formation of Landau levels further altered by rotation and gravitational mass, and thermodynamic quantities (internal energy, specific heat, free energy, entropy, magnetization, and magnetocaloric effect) exhibit a strong dependence on these parameters. In particular, the difference between $ m^\ast$ and $ m_G$ influences magnetization and the magnetocaloric effect, with negative rotations potentially inducing a cooling effect when these masses are distinct. We conclude that rotational effects and effective mass properties are crucial for understanding the thermodynamics of electronic systems under magnetic fields, with implications for thermal modulation in semiconductor materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
21 pages, 44 figures
Typical reconstruction limit and phase transition of maximum entropy method
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-07 20:00 EDT
Masaru Hitomi, Masayuki Ohzeki
We investigate the dependence of the maximum entropy method (MEM) reconstruction performance on the default model. The maximum entropy method is a reconstruction technique that utilizes prior information, referred to as the default model, to recover original signals from observed data, and it is widely used in underdetermined systems. The broad applications have been reported in fields ranging from the analysis of observational data in seismology and astronomy, to large-scale computations in quantum chemistry, and even in social sciences such as linguistics. However, a known drawback of MEM is that its results depend on the assumed default model. In this study, we employ the replica method to elucidate how discrepancies in the default model affect the reconstruction of signals with specific distributions. We report that in certain cases, even small discrepancies can induce phase transitions, leading to reconstruction failure. Additionally, by comparing MEM with reconstruction based on L1-norm optimization, a method proposed in recent years, we demonstrate that MEM exhibits lower reconstruction accuracy under certain conditions.
Statistical Mechanics (cond-mat.stat-mech)
9 pages, 5 figures
Metastable short-range charge order in superconducting CuxTiSe2
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-07 20:00 EDT
Thomas Sutter, Colleen Lindenau, Shivani Sharma, Andrei Fluerasu, Lutz Wiegart, Goran Karapetrov, Anshul Kogar, Xiaoqian M Chen
In a vast array of materials, including cuprates, transition metal dichalcogenides (TMDs) and rare earth tritellurides, superconductivity is found in the vicinity of short-range charge density wave (CDW) order. The crossover from long-range to short-range charge order often occurs as quenched disorder is introduced, yet it is unclear how this disorder disrupts the CDW. Here, using x-ray photon correlation spectroscopy (XPCS), we investigate the prototypical TMD superconductor CuxTiSe2 and show that disorder induces substantial CDW dynamics. We observed the CDW phase fluctuation on a timescale of minutes to hours above the nominal transition temperature while the order parameter amplitude remains finite. These long timescale fluctuations prevent the system from finding the global free energy minimum upon cooling and ultimately traps it in a short-range ordered metastable state. Our findings demonstrate how correlated disorder can give rise to a distinct mechanism of domain formation that may be advantageous to the emergence of superconductivity.
Strongly Correlated Electrons (cond-mat.str-el)
Magnetic-field-tuned randomness in inhomogeneous altermagnets
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-07 20:00 EDT
Anzumaan R. Chakraborty, Jörg Schmalian, Rafael M. Fernandes
Altermagnetic (AM) states have compensated collinear magnetic configurations that are invariant under a combination of real-space rotation and time reversal. While these symmetries forbid a direct bilinear coupling of the AM order parameter with a magnetic field, they generally enable piezomagnetism, manifested as a trilinear coupling with magnetic field and strain. Here, we show that, because of this coupling, in an altermagnet subjected to random strain, the magnetic field triggers an effective random field conjugate to the AM order parameter, providing a rare realization of a tunable random-field Ising model. Specifically, we find two competing effects promoted by an external magnetic field: an increasing random-field disorder, which suppresses long-range AM order, and an enhanced coupling to elastic fluctuations, which favors AM order. By solving the corresponding random-field transverse-field Ising model via a mean-field approach, we obtain the temperature-magnetic field phase diagram of an inhomogeneous AM state for different strengths of random-strain disorder, unveiling the emergence of a field-induced reentrant AM phase. We also discuss the fingerprints of this rich behavior on several experimentally-accessible quantities, such as the shear modulus, the elasto-caloric effect coefficient, and the AM order parameter. Our results reveal an unusual but experimentally-feasible path to tune AM order with uniform magnetic fields.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Optical detection of charge defects near a graphene transistor using the Stark shift of fluorescent molecules
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-07 20:00 EDT
Carlotta Ciancico, Iacopo Torre, Bernat Terrés, Alvaro Moreno, Robert Smit, Kenji Watanabe, Takashi Taniguchi, Michel Orrit, Frank Koppens, Antoine Reserbat-Plantey
Two-dimensional crystals and their heterostructures unlock access to a class of photonic devices, bringing nanophotonics from the nanometer scale down to the atomic level where quantum effects are relevant. Single-photon emitters (SPEs) are central in quantum photonics as quantum markers linked to their electrostatic, thermal, magnetic, or dielectric environment. This aspect is exciting in two-dimensional (2D) crystals and their heterostructures, where the environment can be abruptly modified through vertical stacking or lateral structuring, such as moiré or nano-patterned gates. To further develop 2D-based quantum photonic devices, there is a need for quantum markers that are capable of integration into various device geometries, and that can be read out individually, non-destructively, and without additional electrodes. Here, we show how to optically detect charge carrier accumulation using sub-GHz linewidth single-photon emitters coupled to a graphene device. We employ the single molecule Stark effect, sensitive to the electric fields generated by charge puddles, such as those at the graphene edge. The same approach enables dynamic sensing of electronic noise, and we demonstrate the optical read-out of low-frequency white noise in a biased graphene device. The approach described here can be further exploited to explore charge dynamics in 2D heterostructures using quantum emitter markers.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
4 figures
Successive Antiferromagnetic Transition in the Frustrated Compound CeMgIn
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-07 20:00 EDT
Kou Onishi, Hitoshi Sugawara, Takahiro Sakurai, Hitoshi Ohta, Eiichi Matsuoka
We report on the magnetic, transport, and thermal properties of the hexagonal ZrNiAl-type compound CeMgIn with Ce atoms forming a distorted kagome network. This compound exhibits successive antiferromagnetic transition at $ T_\text{N1} =$ 2.1 K, $ T_\text{N2} =$ 1.7 K, and possibly $ T_\text{N3} =$ 1.3 K. The electrical resistivity exhibits a minimum at 11 K and a nonlogarithmic increase with decreasing temperature down to $ T_\text{N2}$ . We found that CeMgIn is the first ZrNiAl-type compound whose resistivity increase can be well explained by considering a model in which the electron-spin scattering is enhanced by the magnetic frustration and the Ruderman-Kittel-Kasuya-Yosida interaction. These results suggest that CeMgIn is a notable compound whose physical properties are strongly affected by geometrical frustration. Since the Sommerfeld coefficient is 97 mJ/mol K$ ^2$ , CeMgIn is classified as a moderate heavy-fermion compound.
Strongly Correlated Electrons (cond-mat.str-el)
5 pages, 6 figures
J. Phys. Soc. Jpn. 94, 044706 (2025)
The strain-stiffening critical exponents in polymer networks and their universality
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-07 20:00 EDT
Zibin Zhang, Eran Bouchbinder, Edan Lerner
Disordered athermal biopolymer materials, such as collagen networks that constitute a major component in extracellular matrices and various connective tissues, are initially soft and compliant but stiffen dramatically under strain. Such network materials are topologically sub-isostatic and feature strong rigidity scale separation between the bending and stretching response of the constituent polymer fibers. Recently, a comprehensive scaling theory of the athermal strain-stiffening phase transition has been developed, providing predictions for all critical exponents characterising the transition in terms of the distance to the critical strain and of the small rigidity scales ratio. Here, we employ large-scale computer simulations, at and away from criticality, to test the analytic predictions. We find that all numerical critical exponents are in quantitative agreement with the analytically-predicted ones. Moreover, we find that all predicted exponents remain valid whether the driving strain is shear, i.e., volume-preserving, or dilation, and independent of the degree of the network’s sub-isostaticity, thus establishing the universality of the strain-stiffening phase transition with respect to the symmetry of the driving strain and the network’s topology.
Soft Condensed Matter (cond-mat.soft), Disordered Systems and Neural Networks (cond-mat.dis-nn), Materials Science (cond-mat.mtrl-sci), Biological Physics (physics.bio-ph)
6 pages, 5 figures + Appendices + Refs
Transfer of active motion from medium to probe via the induced friction and noise
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-07 20:00 EDT
Can activity be transmitted from smaller to larger scales? We report on such a transfer from a homogeneous active medium to a Newtonian spherical probe. The active medium consists of faster and dilute self-propelled particles, modeled as run-and-tumble particles in 1D or as active Brownian particles in 2D. We derive the reduced fluctuating dynamics of the probe valid for arbitrary probe velocity, characterized by a nonlinear friction and a velocity-dependent noise. There appear several distinct regimes: a standard regime where the probe exhibits passive Brownian motion, and peculiar active regimes where the probe becomes self-propelled with high persistence, and its velocity distribution begets peaks at nonzero values. The resulting propulsion speeds and their persistence are quantitatively obtained and are confirmed by numerical simulations of the joint probe-medium system. The emergence of active regimes depends not only on the far-from-equilibrium nature of the medium but also on the probe-medium coupling. In 1D, a soft coupling is necessary, whereas in 2D, more realistic interactions, such as Lennard-Jones, suffice. Our findings thus reveal how, solely via the induced friction and noise, persistence can cross different scales to transfer active motion.
Statistical Mechanics (cond-mat.stat-mech), Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
Topological sorting of magnetic colloidal bipeds
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-07 20:00 EDT
Aneena Rinu Perayil, Piotr Kuświk, Maciej Urbaniak, Feliks Stobiecki, Sapida Akhundzada, Arno Ehresmann, Daniel de las Heras, Thomas M. Fischer
Topologically nontrivial adiabatic loops of the orientation of a homogeneous external magnetic field drive the walking of paramagnetic colloidal bipeds above a deformed quasi-periodic magnetic square pattern. Depending on the topological properties of the loop we can simultaneously control the walking directions of colloidal bipeds as a function of their size and as a function of the size of a deformed unit cell of the pattern. The bipeds walk performing steps with their two feet alternatingly grounding one foot and lifting the other. The step width of the bipeds is given by a set of winding numbers $ (w_x,w_{y})\in Z^2$ – a set of topological invariants – that can only change by integers as we continuously increase the length of the bipeds. We experimentally use this discrete size dependence for the robust sorting of bipeds according to their length.
Soft Condensed Matter (cond-mat.soft)
Soft Matter, 21, 2716-2722, (2025)
Spin-to-orbital angular momentum conversion in non-Hermitian photonic graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-07 20:00 EDT
Zhaoyang Zhang, Pavel Kokhanchik, Zhenzhi Liu, Yutong Shen, Fu Liu, Maochang Liu, Yanpeng Zhang, Min Xiao, Guillaume Malpuech, Dmitry Solnyshkov
Optical beams with orbital angular momentum (OAM) have numerous potential applications, but the means used for their generation often lack crucial on-demand control. In this work, we present a mechanism of converting spin angular momentum (SAM) to OAM in a non-structured beam. The conversion occurs through spin-orbit coupling in a reconfigurable photonic honeycomb lattice with staggering implemented by electromagnetically-induced transparency in an atomic vapor cell. The spin-orbit coupling allows to outcouple the OAM signal from a particular band in a given valley determined by the chirality of light or the lattice staggering, providing a non-zero Berry curvature for generating OAM. The dependence of the output OAM on the chirality of the input beam is the first control knob. The staggering works as a second control knob, flipping the sign of OAM for the fixed chirality. The demonstrated conversion between SAM and OAM is important for optical communications. Our results can be extended to other implementations of paraxial photonic graphene.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
Spin-orbit interactions, time-reversal symmetry, and spin selection
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-07 20:00 EDT
Amnon Aharony, Ora Entin-Wohlman
Spin selective transport is usually associated with spin-orbit interactions. However, these interactions are invariant under time-reversal symmetry, and the Onsager relations and Bardarson’s theorem imply that such interactions cannot yield spin selectivity for transport through a junction between two electronic reservoirs. Here, we review several ways to overcome this restriction, using a Zeeman magnetic field, the Aharonov-Bohm phase, time-dependent electric fields that generate time-dependent spin-orbit interactions, time-dependent transients, more than two terminals, leakage, and more than one level per ion on the junction. Our considerations focus on the transport of noninteracting electrons at low temperatures. A possible connection with the phenomenon of chiral-induced spin selectivity (CISS) is pointed out in one of the systems considered.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
To appear in J. Chem. Phys., special issue honoring Abraham Nitzan
Evaluation of strain and charge-transfer doping in wet-polymeric transferred monolayer MoS2: implications for field effect transistors
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-07 20:00 EDT
C. Abinash Bhuyan, Kishore K. Madapu, K. Prabhakar, Jagnaseni Pradhan, Arup Dasgupta, S R Polaki, Sandip Dhara
Two-dimensional materials offer exceptional tunability of electronic and optical properties via strain and doping engineering. However, the unintentional introduction of polymeric residues during wet chemical 2D film transfer processes such as wet chemical etching and surface energy assisted methods remains critical, yet unexplored. This study systematically investigates the impact of such residues on the optical and electrical properties of monolayer MoS\textsubscript{2} using Raman and photoluminescence spectroscopy. We reveal that polymer residues in transferred films from wet chemical etching induce distinct strain and doping behaviors: PMMA-existed regions exhibit biaxial tensile strain and \textit{p}-type doping, while PMMA-free regions show compressive strain. In contrast, the surface energy assisted transfer method introduces compressive strain and \textit{n}-type doping in the transferred film due to residue interactions. Field-effect transistor measurements corroborate these findings, showing polymer residue-influenced modulation of charge transport. Notably, the surface energy assisted technique minimizes transfer-induced defects, highlighting its superiority for fabricating high-performance 2D optoelectronic devices. These results underscore the critical role of transfer methodologies in tailoring optoelectronic properties and provide practical insights for optimizing 2D material integration in advanced technologies.
Materials Science (cond-mat.mtrl-sci)
20 Pages, 9 figures
Topological defects in polar active matter
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-07 20:00 EDT
Luiza Angheluta, Anna Lång, Emma Lång, Stig Ove Bøe
Polar active matter - including animal herds, aggregates of motile cells and active colloids - often forms coordinated migration patterns, such as flocking. This orderly motion can be disrupted by full-integer topological defects representing localized disturbances where polar alignment is lost. Such polar defects can serve as key organizing centers across scales, sustaining collective behavior, such as swirling motion and other large-scale coherent states. While significant progress in understanding active matter principles have been made in recent years, a quantitative understanding of how topological defects influence active polar matter is needed. We present a brief overview of recent experimental observations in synthetic active colloids and various biological systems. We describe how polar defects mediate dynamical transitions and contribute to the spontaneous emergence of large-scale coherent states. We also discuss theoretical advancements in physical modeling of coupled processes involving polar defects and collective behavior in active polar matter.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
Chemo-mechanical motility modes of partially wetting liquid droplets
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-07 20:00 EDT
We consider a simple thermodynamically consistent model that captures the interplay between autocatalytically reacting surfactants, the Marangoni effect and wetting dynamics. An ambient bath of surfactant acts as a chemostat and provides the system with chemical fuel, thereby driving it away from thermodynamic equilibrium. We find that a positive feedback loop between the local reactions and the Marangoni effect induces surface tension gradients that allow for self-propelled droplets. Besides simple directional motion, we find crawling and shuttling droplets as well as droplets performing random walks, thus exploring the entire substrate. We study the occurring dynamics and show how the observed states emerge from local and global bifurcations. Due to the underlying generic thermodynamic structure, we expect that our results are relevant not only to directly related biomimetic droplet systems but also to structurally similar systems like chemically active phase separating mixtures.
Soft Condensed Matter (cond-mat.soft), Adaptation and Self-Organizing Systems (nlin.AO), Fluid Dynamics (physics.flu-dyn)
Maximal critical temperature dependence on number of layers due to phonon d-wave pairing in hole doped cuprates
New Submission | Superconductivity (cond-mat.supr-con) | 2025-04-07 20:00 EDT
Baruch Rosenstein, B. Ya. Shapiro, Guy Leshem
Recently an apical oxygen atoms vibrations exchange mechanism of d-wave pairing in cuprates was proposed. The phonon mode in an insulating layer generates attraction of holes in metallic cuper oxygen planes. The pairing has a maximum at the crystallographic gamma point leading to d-wave channel. The idea is generalized here to include the in-plane breathers and half - breather modes in a multi-layer cuprate generating the pairing in an adjacent cuper oxygen layer of the same multi-layer. It is demonstrated that the phonon exchange and the spin fluctuation pairing constructively enhance each other since the paramagnon pairing peaks at crystallographic M point. The phonon contribution explains the maximal critical temperature dependence on the number of layers N. It rises equidistantly by 15K from N=1 to N=3 and then saturates. The strength of the onsite Coulomb on site repulsion at optimal doping is to obtain the observed values of maximal critical temperature in the intermediate range of the effective on-site repulsion U=(1.5-2) eV, smaller than commonly used in purely in-plane (spin fluctuation) theory of high temperature superconductivity.
Superconductivity (cond-mat.supr-con)
Accepted to PRB
Multicolor phonon excitation in terahertz cavities
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-07 20:00 EDT
Omer Yaniv, Dominik M. Juraschek
Driving materials using light with more than one frequency component is an emerging technique, enabled by advanced pulse-shaping capabilities in recent years. Here, we translate this technique to lattice vibrations, by exciting multicolor phonons using terahertz cavities. In contrast to light, phonon frequencies are determined by the crystal structure and cannot readily be changed. We overcome this problem by tuning the frequencies of phonon polaritons in terahertz cavities to achieve the desired frequency ratios necessary for phononic Lissajous figures. This methodology enables dynamical crystallographic symmetry breaking and the creation of staggered phonon angular momentum and magnetic moment patterns.
Materials Science (cond-mat.mtrl-sci), Optics (physics.optics)
Exotic Doublon-Holon Pairing State in Photodoped Mott Insulators
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-07 20:00 EDT
Ryota Ueda, Madhumita Sarkar, Zala Lenarčič, Denis Golež, Kazuhiko Kuroki, Tatsuya Kaneko
We demonstrate the existence of a unique pairing state in photodoped Mott insulators on ladder geometries, characterized by quasi-long-ranged doublon-holon correlations, using the density matrix renormalization group method. This phase exhibits doublon-holon pairing correlations with opposite signs along the rung and chain directions, reminiscent of d-wave pairing in chemically doped ladder systems. By constructing the phase diagram, we reveal that the doublon-holon pairing state emerges between the spin-singlet phase and the charge-density-wave/$ \eta$ -pairing phase. Our study suggests that the interplay of charge, spin, and $ \eta$ -spin degrees of freedom can give rise to exotic quantum many-body states in photodoped Mott insulators.
Strongly Correlated Electrons (cond-mat.str-el)
8+10 pages, 4+8 figures
Chiral phonons in polar LiNbO3
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-07 20:00 EDT
Hiroki Ueda, Abhishek Nag, Carl P. Romao, Mirian García-Fernández, Ke-Jin Zhou, Urs Staub
Quasiparticles describe collective excitations in many-body systems, and their symmetry classification is of fundamental importance because they govern physical processes on various timescales, e.g., excited states, transport phenomena, and phase transitions. Recent studies have revealed that quasiparticles can possess chirality and that this degree of freedom leads to various important phenomena. Among them, chiral phonons have recently attracted significant interest because of their intrinsic magnetism, which non-trivially bridges the spin system and the lattice. Here, we directly prove the presence of chiral phonons in a prototypical polar crystal LiNbO3. Our demonstration adds a polar crystal in the showcase of materials hosting chiral phonons and, furthermore, creates a substantial potential in chiral phononics because of its expected in-situ switchable phonon chirality and associated control of phonon angular momentum.
Strongly Correlated Electrons (cond-mat.str-el)
15 pages, 3 figures
A silicon spin vacuum: isotopically enriched $^{28}$silicon-on-insulator and $^{28}$silicon from ultra-high fluence ion implantation
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-07 20:00 EDT
Shao Qi Lim, Brett C. Johnson, Sergey Rubanov, Nico Klingner, Bin Gong, Alexander M. Jakob, Danielle Holmes, David N. Jamieson, Jim S. Williams, Jeffrey C. McCallum
Isotopically enriched silicon (Si) can greatly enhance qubit coherence times by minimizing naturally occurring $ ^{29}$ Si which has a non-zero nuclear spin. Ultra-high fluence $ ^{28}$ Si ion implantation of bulk natural Si substrates was recently demonstrated as an attractive technique to ultra-high $ ^{28}$ Si isotopic purity. In this work, we apply this $ ^{28}$ Si enrichment process to produce $ ^{28}$ Si and $ ^{28}$ Si-on-insulator (SOI) samples. Experimentally, we produced a $ ^{28}$ Si sample on natural Si substrate with $ ^{29}$ Si depleted to 7ppm (limited by measurement noise floor), that is at least 100 nm thick. This is achieved with an ion energy that results in a sputter yield of less than one and a high ion fluence, as supported by simulations. Further, our simulations predict the $ ^{29}$ Si and $ ^{30}$ Si depletion in our sample to be less than 1ppm. In the case of SOI, ion implantation conditions are found to be more stringent than those of bulk natural Si in terms of minimizing threading dislocations upon subsequent solid phase epitaxy annealing. Finally, we report the observation of nanoscopic voids in our $ ^{28}$ SOI and $ ^{28}$ Si samples located in the depth region between the surface and 70~nm. These voids appear to be stabilized by the presence of gold impurities and can be annealed out completely by a standard SPE annealing protocol at 620°C for 10 minutes in the absence of gold.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph), Quantum Physics (quant-ph)
12 pages, 4 figures
Magnetically Compensated Nanometer-thin Ga-Substituted Yttrium Iron Garnet (Ga:YIG) Films with Robust Perpendicular Magnetic Anisotropy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-07 20:00 EDT
Carsten Dubs, Oleksii Surzhenko
Magnetically full or partially compensated insulating ferrimagnets with perpendicular magnetic anisotropy (PMA) offer valuable insights into fundamental spin-wave physics and high-speed magnonic applications. This study reports on key magnetic parameters of nanometer-thin Ga substituted yttrium iron garnet (Ga:YIG) films with saturation magnetization 4PiMs below 200 G. Vibrating sample magnetometry (VSM) is used to determine the remanent magnetization 4PiMr and the polar orientation of the magnetic easy axis in samples with very low net magnetic moments. Additionally, the temperature dependence of the net magnetization of magnetically compensated Ga:YIG films, with compensation points Tcomp near room temperature is investigated. For films with remanent magnetization values below 60 G at room temperature, the compensation points Tcomp are determined and correlated with their Curie temperatures TC. Ferromagnetic resonance (FMR) measurements at 6.5 GHz show that the FMR linewidths Delta H FWHM correlate inversely proportional with the remanent magnetization. The reduced saturation magnetization in the Ga:YIG films leads to a significant increase in the effective magnetization 4PiMeff and thus enables films with robust PMA. This opens up a new parameter space for the fine-tuning of potential magnonic spin-wave devices on commonly used GGG substrates.
Materials Science (cond-mat.mtrl-sci)
main text: 18 pages, 6 figures, Supporting Information: 6 pages, 1 figure, 2 tables
Signatures of Orbital Order and Disorder in Fluoro-Perovskites with $t_{2g}$ Electronic Degeneracies
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-07 20:00 EDT
C. A. Crawford, C. I. Hiley, J. Gainza, C. Ritter, R. I. Walton, Mark S. Senn
A detailed high-resolution, variable temperature powder diffraction study of the fluoro-perovskites NaFeF$ _3$ and NaCoF$ _3$ is performed to probe their orbital ordering transitions. Through analysis of the symmetry adapted macrostrains and atomic distortions, we show that NaFeF$ 3$ undergoes a C-type orbital order transition associated with the $ t{2g}^4$ states of Fe$ ^{2+}$ . Counter-intuitively, the phase transition leading to the orbital order appears second order-like, which contradicts the thermodynamic requirements for electronic and isosymmeric phase transitions, implying that there must be an associated hidden symmetry breaking. On the other hand, for NaCoF$ _3$ , consideration of the symmetry adapted strains allows us to confidently rule out the occurrence of any long-range orbital orders down to 4 K. Since NaCoF$ 3$ is an insulator with quenched orbital angular momentum at this temperature, our findings point towards a novel kind of orbital disorder associated to the $ t{2g}^5$ electronic degeneracy.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
8 pages, 5 figures
Competition of light- and phonon-dressing in microwave-dressed Bose polarons
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-04-07 20:00 EDT
G. M. Koutentakis, S. I. Mistakidis, F. Grusdt, H. R. Sadeghpour, P. Schmelcher
We theoretically investigate the stationary properties of a spin-1/2 impurity immersed in a one-dimensional confined Bose gas. In particular, we consider coherently coupled spin states with an external field, where only one spin component interacts with the bath, enabling light dressing of the impurity and spin-dependent bath-impurity interactions. Through detailed comparisons with ab-initio many-body simulations, we demonstrate that the composite system is accurately described by a simplified effective Hamiltonian. The latter builds upon previously developed effective potential approaches in the absence of light dressing. It can be used to extract the impurity energy, residue, effective mass, and anharmonicity induced by the phononic dressing. Light-dressing is shown to increase the polaron residue, undressing the impurity from phononic excitations because of strong spin coupling. For strong repulsions-previously shown to trigger dynamical Bose polaron decay (a phenomenon called temporal orthogonality catastrophe), it is explained that strong light-dressing stabilizes a repulsive polaron-dressed state. Our results establish the effective Hamiltonian framework as a powerful tool for exploring strongly interacting polaronic systems and corroborating forthcoming experimental realizations.
Quantum Gases (cond-mat.quant-gas), Other Condensed Matter (cond-mat.other), Atomic Physics (physics.atom-ph), Quantum Physics (quant-ph)
35 pages. 6 figures, Submission to SciPost
Martingale approach for first-passage problems of time-additive observables in Markov processes
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-07 20:00 EDT
We develop a method based on martingales to study first-passage problems of time-additive observables exiting an interval of finite width in a Markov process. In the limit that the interval width is large, we derive generic expressions for the splitting probability and the cumulants of the first-passage time. These expressions relate first-passage quantities to the large deviation properties of the time-additive observable. We find that there are three qualitatively different regimes depending on the properties of the large deviation rate function of the time-additive observable. These regimes correspond to exponential, super-exponential, or sub-exponential suppression of events at the unlikely boundary of the interval. Furthermore, we show that the statistics of first-passage times at both interval boundaries are in general different, even for symmetric thresholds and in the limit of large interval widths. While the statistics of the times to reach the likely boundary are determined by the cumulants of the time-additive observables in the original process, those at the unlikely boundary are determined by a dual process. We obtain these results from a one-parameter family of positive martingales that we call Perron martingales, as these are related to the Perron root of a tilted version of the transition rate matrix defining the Markov process. Furthermore, we show that each eigenpair of the tilted matrix has a one-parameter family of martingales. To solve first-passage problems at finite thresholds, we generally require all one-parameter families of martingales, including the non-positive ones. We illustrate this by solving the first-passage problem for run-and-tumble particles exiting an interval of finite width.
Statistical Mechanics (cond-mat.stat-mech), Probability (math.PR)
45 pages, 6 figures
J. Phys. A: Math. Theor. 58, 145002 (2025)
Graph theory and tunable slow dynamics in quantum East Hamiltonians
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-07 20:00 EDT
Heiko Georg Menzler, Mari Carmen Bañuls, Fabian Heidrich-Meisner
We show how graph theory concepts can provide an insight into the origin of slow dynamics in systems with kinetic constraints. In particular, we observe that slow dynamics is related to the presence of strong hierarchies between nodes on the Fock-space graph in the particle occupation basis, which encodes configurations connected by a given Hamiltonian. To quantify hierarchical structures, we develop a measure of centrality of the nodes, which is applicable to generic Hamiltonian matrices and inspired by established centrality measures from graph theory. We illustrate these ideas in the quantum East (QE) model. We introduce several ways of detuning nodes in the corresponding graph that alter the hierarchical structure, defining a family of QE models. We numerically demonstrate how these detunings affect the degree of non-ergodicity on finite systems, as evidenced by both the time dependence of density autocorrelations and eigenstate properties in the detuned QE models.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
17 pages, 12 figures
Hierarchical woven fibrillar structures in developing single gyroids in butterflies
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-07 20:00 EDT
Anna-Lee Jessop, Peta L. Clode, Martin Saunders, Myfanwy E. Evans, Stephen T. Hyde, James N. McPherson, Kasper S. Pederson, Jacob J.K. Kirkensgaard, Nipam H. Patel, K.A. DeMarr, W. Owen McMillan, Bodo D. Wilts, Gerd E. Schroeder-Turk
Nature offers a remarkable diversity of nanomaterials that have extraordinary functional and structural properties. Intrinsic to nature is the impressive ability to form complex ordered nanomaterials via self-organization. One particularly intriguing nanostructure is the Gyroid, a network-like structure exhibiting high symmetry and complex topology. Although its existence in cells and tissues across many biological kingdoms is well documented, how and why it forms remains elusive and uncovering these formation mechanisms will undoubtedly inform bioinspired designs. A beautiful example is the smooth single gyroid that is found in the wing scales of several butterflies, where it behaves as a photonic crystal generating a vibrant green colour. Here, we report that the gyroid structures of the Emerald-patched Cattleheart, Parides sesostris, develop as woven fibrillar structures, disputing the commonly held assumption that they form as smooth constructs. Ultramicroscopy of pupal tissue reveals that the gyroid geometry consists of helical weavings of fibres, akin to hyperbolic line patterns decorating the gyroid. Interestingly, despite their fibrillar nature, electron diffraction reveals the absence of crystalline order within this material. Similar fibrillar structures are also observed in the mature wing scales of P. sesostris specimens with surgically altered pupal development, leading to a blue colouration. Our findings not only introduce a fundamentally new variation of the gyroid in biology but also have significant implications for our understanding of its formation in nature.
Soft Condensed Matter (cond-mat.soft)
Supersolid phase in two-dimensional soft-core bosons at finite temperature
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-04-07 20:00 EDT
Sebastiano Peotta, Gabriele Spada, Stefano Giorgini, Sebastiano Pilati, Alessio Recati
The supersolid phase of soft-core bosons in two dimensions is investigated using the self-consistent Hartree-Fock and quantum Monte Carlo methods. An approximate phase diagram at finite temperatures is initially constructed using the mean-field approach, which is subsequently validated through precise path-integral simulations, enabling a microscopic characterization of the various phases. Superfluid and melting/freezing transitions are analyzed through the superfluid density and the long-range behavior of correlation functions associated with positional and orientational order, in accordance with the general picture of Berezinskii-Kosterlitz-Thouless transitions. A broad region at low temperatures is identified where the supersolid phase exists, separating the uniform superfluid phase from the normal quasi-crystal phase. Additionally, a potential intermediate hexatic phase with quasi long-range orientational order is identified in a narrow region between the normal solid and fluid phases. These findings establish self-consistent Hartree-Fock theory beyond the local density approximation as an effective tool, complementary to computationally intensive quantum Monte Carlo simulations, for investigating the melting of the supersolid phase and the possible emergence of the hexatic superfluid phase in bosonic systems with various interaction potentials.
Quantum Gases (cond-mat.quant-gas), Statistical Mechanics (cond-mat.stat-mech), Computational Physics (physics.comp-ph), Quantum Physics (quant-ph)
23 pages, 11 figures
Mitigating boundary effects in finite temperature simulations of false vacuum decay
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-04-07 20:00 EDT
Kate Brown, Ian G. Moss, Thomas P. Billam
The physics of false vacuum decay during first-order phase transitions in the early universe may be studied in the laboratory via cold-atom analogue simulators. However, a key difference between analogue experiments and the early universe is the trap potential confining the atoms. Rapid seeded bubble nucleation has been shown to occur at the boundary of typical trap potentials, obscuring the bulk bubble nucleation rate. This difficulty must be overcome in order to reliably probe the bulk bubble nucleation rate in an analogue simulator experiment. In this paper we show that, at finite temperature, this deleterious boundary nucleation can be mitigated by adding a ‘trench’ to the potential, effectively screening the boundary with a region of higher atomic density. We show that this technique is effective in two different cold-atom analogue systems, but is not needed in ferromagnetic analogue simulators.
Quantum Gases (cond-mat.quant-gas)
8 pages, 7 figures
Multiscale Energy Spreading in Hard-Particle Chains
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-07 20:00 EDT
We consider a one-dimensional array of particles interacting via an infinite well potential. We explore the properties of energy spreading from an initial state where only a group of particles has non-zero velocities while others are resting. We characterize anomalous diffusion of the active domain via moments and entropies of the energy distribution. Only in the special cases of a single-well potential (hard-particle gas) and of the distance between the particles being half of the potential width does the diffusion have a single scale; otherwise, a multiscale anomalous diffusion is observed.
Statistical Mechanics (cond-mat.stat-mech), Cellular Automata and Lattice Gases (nlin.CG)
Dynamic Training Enhances Machine Learning Potentials for Long-Lasting Molecular Dynamics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-07 20:00 EDT
Ivan Žugec, Tin Hadži Veljković, Maite Alducin, J. Iñaki Juaristi
Molecular Dynamics (MD) simulations are vital for exploring complex systems in computational physics and chemistry. While machine learning methods dramatically reduce computational costs relative to ab initio methods, their accuracy in long-lasting simulations remains limited. Here we propose dynamic training (DT), a method designed to enhance model performance over extended MD simulations. Applying DT to an equivariant graph neural network (EGNN) on the challenging system of a hydrogen molecule interacting with a palladium cluster anchored to a graphene vacancy demonstrates a superior prediction accuracy compared to conventional approaches. Crucially, the DT architecture-independent design ensures its applicability across diverse machine learning potentials, making it a practical tool for advancing MD simulations.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
Observation of Temperature Effects in False Vacuum Decay
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-04-07 20:00 EDT
Riccardo Cominotti (1), Cosetta Baroni (1,2), Chiara Rogora (1), Diego Andreoni (1), Giacomo Guarda (1), Giacomo Lamporesi (1), Gabriele Ferrari (1), Alessandro Zenesini (1) ((1) Pitaevskii BEC Center, CNR-INO and Dipartimento di Fisica, Universita’ di Trento, Trento, Italy, and Trento Institute for Fundamental Physics and Applications, INFN, Trento, Italy (2) Institute for Quantum Optics and Quantum Information (IQOQI) and Institute for Experimental Physics, University of Innsbruck, Innsbruck, Austria)
Metastability is a phenomenon encountered in many different physical systems, ranging from chemical reactions to magnetic structures. The characteristic decay timescale from a metastable to a stable state is not always straightforward to estimate since it depends on the microscopic details of the system. A paradigmatic example in quantum field theories is the decay of the false vacuum, manifested via the nucleation of bubbles. In this paper, we measure the temperature dependence of the timescale for the false vacuum decay mechanism in an ultracold atomic quantum spin mixture which exhibits ferromagnetic properties. Our results show that the false vacuum decay rate scales with temperature as predicted by the finite-temperature extension of the instanton theory, and confirm atomic systems as an ideal platform where to study out-of-equilibrium field theories.
Quantum Gases (cond-mat.quant-gas), Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Phenomenology (hep-ph), High Energy Physics - Theory (hep-th), Quantum Physics (quant-ph)
10 pages, 8 figures
Splash in an inhomogeneous gas in one dimension: Exact analysis and molecular dynamics simulations
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-07 20:00 EDT
We investigate the splash phenomenon resulting from the energy input at the interface between a vacuum and an inhomogeneous gas with density profile $ \rho(r) = \rho_0 r^{-\beta}$ . The energy input causes the formation of ballistic spatters that propagate into the vacuum, leading to a decay of the total energy in the inhomogeneous medium following a power law, $ E(t) \sim t^{-\delta_s}$ . We determine exactly the exponents $ \delta_s$ by solving the Euler equation using a self-similar solution of second kind for different values of $ \beta$ . These exponents are further validated through event-driven molecular dynamics simulations. The determination of these exponents also allows us to numerically determine the spatio-temporal dependence of the density, velocity and temperature.
Statistical Mechanics (cond-mat.stat-mech)
Large plastic deformation of voids in crystals
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-07 20:00 EDT
Jalal Smiri, Joseph Paux, Oguz Umut Salman, Ioan R. Ionescu
The mechanisms of void growth and coalescence are key contributors to the ductile failure of crystalline materials. At the grain scale, single crystal plastic anisotropy induces large strain localization leading to complex shape evolutions. In this study, an Arbitrary Lagrangian-Eulerian (ALE) framework for 2D crystal plasticity combined with dynamic remeshing is used to study the 2D shape evolution of cylindrical voids in single crystals. The large deformation and shape evolution of the voids under two types of loading are considered: (i) radial and (ii) uni-axial loadings. In both cases, the voids undergo complex shape evolutions induced by the interactions between slip bands, lattice rotations and large strain phenomena. In case (i), the onset of the deformation revealed the formation of a complex fractal network of slip bands around the voids. Then, large deformations unearth an unexpected evolution of the slip bands network associated with significant lattice rotations, leading to a final hexagonal shape for the void. In case (ii), we obtain shear bands with very large accumulated plastic strain (> 200%) compared to the macroscopic engineering strains (< 15%). A high dependence between crystalline orientations, slip band localization and therefore shape evolution was observed, concluding in a high dependency between crystalline orientation and void shape elongation, which is of prime importance regarding coalescence of the voids, thus to the formation of macro-cracks.
Materials Science (cond-mat.mtrl-sci)
40 pages, 13 figures
Optical high harmonic generation in Dirac materials
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-07 20:00 EDT
S. Rakhmanov, K. Matchonov, H. Yusupov, K. Nasriddinov, D. Matrasulov
We study high-order harmonic generation by optically driven one- and two-dimensional hydrogenlike atoms formed by Coulomb imurities in graphene. The time-dependent Dirac equations with Coulomb plus time-periodic monochromatic field potentials are solved for both cases. Such characteristics of the optical high harmonic generation, as average dipole moment and high harmonic generation spectra, are computed. A sketch for table-top experimental realization of the considered models is proposed.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Eur. Phys. J. B 98, 35 (2025)
Quantum geometry of the surface states of rhombohedral graphite and its effects on the surface superconductivity
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-07 20:00 EDT
Guodong Jiang, Tero Heikkilä, Päivi Törmä
We investigate the quantum geometry of rhombohedral graphite/graphene (RG) surface electronic states and its effects on superconductivity. We find that the RG surface bands have a non-vanishing quantum metric at the center of the drumhead region, and the local inequality between quantum metric and Berry curvature is an equality. Therefore, their quantum geometry is analogous to the lowest Landau level (LLL). The superconducting order parameters on the two surface orbitals of RG can be polarized by the surface potential, which boosts the superconducting transition in trilayer RG triggered by the displacement field. Analyzing the superfluid properties of multilayer RG, we make a connection with the topological heavy fermion model suggested to describe magic-angle twisted bilayer graphene (MATBG). It shows that RG fits in an unusual heavy-fermion picture with the flattest part of the surface bands carrying a nonzero supercurrent. These results may constrain the models constructed for the correlated phases of RG.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Superconductivity (cond-mat.supr-con)
Towards data analysis with diagrammatics
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-04-07 20:00 EDT
Systems with many interacting stochastic constituents are fully characterized by their free energy. Computing this quantity is therefore the objective of various approaches, notably perturbative expansions, which are applied in problems ranging from high-dimensional statistics to complex systems. However, a lot of these techniques are complicated to apply in practice because they lack a sufficient organization of the terms of the perturbative series. In this manuscript, we tackle this problem by using Feynman diagrams, extending a framework introduced earlier to the case of free energies at fixed variances. These diagrammatics do not require the theory to expand around to be Gaussian, which allows its application to the free energy of a spin system studied to derive message-passing algorithms by Maillard et al. 2019. We complete their perturbative derivation of the free energy in the thermodynamic limit. Furthermore, we derive resummations to estimate the entropies of poorly sampled systems requiring only limited statistics and we revisit earlier approaches to compute the free energy of the Ising model, revealing new insights due to the extension of our framework to the free energy at fixed variances. We expect our approach to be useful also for future applications, notably for problems of high-dimensional statistics, like matrix factorization, and the study of complex networks.
Statistical Mechanics (cond-mat.stat-mech), Disordered Systems and Neural Networks (cond-mat.dis-nn)
21 pages, 2 figures