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Physics Condensed Matter

cond-mat Watch Condensed Matter

Friday 21 November

Mesoscale and Nanoscale Physics

A topological field-effect memristor

Manuel Meyer, Selena Barragan, Sergey Krishtopenko et al. (+13 more)

Overcoming the limitations of the von Neumann architecture requires new computational paradigms capable of solving complex problems efficiently. Quantum and neuromorphic computing rely on unconventional materials and device functionalities, yet achieving resilience to imperfections and reliable operation remains a major challenge. This has motivated growing interest in topological materials that provide robust and low-power operation while preserving coherence. However, integrating coherent topological transport with non-volatile memory functionality in a single reconfigurable device has remained challenging. In this work, we demonstrate a topological field-effect memristor based on inverted InAs/GaInSb/InAs trilayer quantum wells operating in the quantum spin Hall regime. The intrinsic floating-gate behavior allows one to reconfigure the transistor functionality into memristive functionality with broad electric-field tunability. Unlike other memristor implementations, one resistance state is governed entirely by dissipationless, coherent transport through helical edge channels, while the other arises from incoherent bulk conduction. By combining electrically tunable coherent and incoherent transport with memory functionality, our device realizes a prototypical topological electronic element that integrates coherent transport and adaptive memristive behavior, paving the way for hybrid quantum-neuromorphic architectures.
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All authors Manuel Meyer, Selena Barragan, Sergey Krishtopenko, Adriana Wolf, Monika Emmerling, Sebastian Schmid, Jean-Baptiste Rodriguez, Eric Tournie, Benoit Jouault, Gerald Bastard, Frederic Teppe, Victor Lopez-Richard, Ovidiu Lipan, Lukas Worschech, Sven Höfling, Fabian Hartmann

Strongly Correlated Electrons

Electron Hydrodynamics: Viscosity Tensor and effects of a Magnetic field

Anubhav Srivastava and Subroto Mukerjee

Transport due to electrons in ultra-clean two dimensional systems can be hydrodynamic in nature with the momentum of the electrons being conserved in the bulk. This hydrodynamic behavior coupled with effects of Berry curvature arising from band structure can give rise to novel vortical transport coefficients relating the stress tensor to gradients in the electrostatic potential and temperature. These coefficients have been calculated in the absence of a magnetic field and have been shown to depend only on the equilibrium distribution function~\cite{Chadha_Mukerjee2024}. In this paper, we first obtain an expression for the viscosity tensor and show that the Berry curvature generates odd components of the viscosity tensor arising from the intrinsic angular momentum of the Bloch wavepackets. We calculate the viscosity tensor for a two-dimensional microscopic model of tilted Dirac cones. We next obtain the vortical coefficients and the viscosity tensor in the presence of a magnetic field and extend the Onsager relations for them to include both the magnetic field and the Berry curvature. We show that the field dependence of the coefficients manifests itself in the non-equilibrium part of the distribution function and calculate them to second order in the electron-electron scattering time. We explicitly show that the expressions we obtain are consistent with the Onsager relations.
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Materials Science

New insights into the magnetism of DyCo$_{5}$

Alena Vishina, Konstantin Skokov, Hiroki Tsuchiura et al. (+5 more)

In this work, we present the first magnetization measurements of DyCo$_5$ single crystals in magnetic fields up to 14 T, spanning a temperature range up to 600 K. Our investigation reveals several unique features, including a significant magnetization anisotropy and an observed minimum in spontaneous magnetization near the compensation point, phenomena not previously reported. This work also uncovers the complex magnetic behavior of DyCo$_5$, with a pronounced interplay between the Dy and Co sublattices, each exhibiting distinct temperature-dependent magnetic properties. The combination of dynamical mean-field theory (DMFT), atomistic spin-dynamics (ASD) simulations, and the Effective Spin Model (ESM) for rare-earth compounds successfully explains the experimental data across both low and high temperatures. Our theoretical approach not only explains the observed magnetic anisotropy and the behavior near the compensation temperature but also successfully reproduces key experimental features such as the saturation behavior at high fields and the evolution of the magnetic moment at different temperatures.
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All authors Alena Vishina, Konstantin Skokov, Hiroki Tsuchiura, Patrik Thunström, Alex Aubert, Oliver Gutfleisch, Olle Eriksson, Heike C. Herper

Materials Science

Low-to-mid Al content ($x\sim$ 0-0.56) Al$_x$In$_{1-x}$N layers deposited on Si(100) by radio-frequency sputtering

R. Blasco, S. Valdueza-Felip, D. Montero et al. (+3 more)

Radio-frequency (RF) sputtering is a low-cost technique for the deposition of large-area single-phase AlInN on silicon layers with application in photovoltaic devices. Here, the effect of the Al mole fraction x from 0 to 0.56 on the structural, morphological, electrical, and optical properties of $n$ Al$_x$In$_{1-x}$N layers deposited at 550 $^\circ$C on p-Si(100) by RF sputtering is studied. X-ray diffraction data show a wurtzite structure oriented along the c-axis in all samples, where the full width at half maximum of the rocking curve around the InN (0002) diffraction peak decreases from $\sim 9^\circ$ to $\sim 3^\circ$ while incorporating Al to the AlInN layer. The rootmean-square surface roughness, estimated from atomic force microscopy, evolves from 20 nm for InN to 1.5 nm for Al$_{0.56}$In$_{0.44}$N. Low-temperature photoluminescence spectra show a blueshift of the emission energy from 1.59 eV (779 nm) for InN to 1.82 eV (681 nm) for Al$_{0.35}$In$_{0.65}$N according to the Al content rise. Hall effect measurements of Al$_x$In$_{1-x}$N ($0<x <0.35$) on sapphire samples grown simultaneously point to a residual n-type carrier concentration in the 1021 cm$^{-3}$ range. The developed n-AlInN/p-Si junctions present promising material properties to explore their performance operating as solar cell devices.
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All authors R. Blasco, S. Valdueza-Felip, D. Montero, M. Sun, J. Olea, F. B. Naranjo

Superconductivity

Unconventional Geometric Phase in Twisted Junction of Cuprates

Zhigang Song and Kai Chang

Originally introduced in optics, the Pancharatnam-Berry phase is a general concept of geometric phase defined for any two interfering polarization states. In electronic systems, however, its counterpart has long been overlooked due to the absence of electron polarization. Here, using large-scale first-principles calculations, we investigate the electronic structure of twisted bilayer Bi2Sr2CaCu2O8. We find spontaneous spin polarization and the emergence of hidden flat bands at the interface between atomic layers. Most notably, we discover an unconventional geometric phase analogous to the Pancharatnam-Berry phase in optics. This electronic geometric phase exerts opposite effects on superconducting currents of opposite chirality, enabling twisted cuprates to act as a filter for chiral superconducting current-even if the ground state itself is non-chiral.
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Quantum Gases

Pair scattering from time-modulated impurity in the Bose-Hubbard model

Neda Ahmadi, Ameneh Sheikhan and Corinna Kollath

We investigate scattering phenomena in a one-dimensional attractive Bose-Hubbard model with a time-periodically modulated impurity. We analyze both single-particle and pair (doublon) transmission, exploring a range of interaction strengths and drive amplitudes. Our exact numerical results reveal excellent quantitative agreement with analytical predictions in the high-frequency limit. At intermediate and weak attractive interactions, we observe significant pair dissociation and the emergence of dynamically localized single-particle modes. These features are reminiscent of Floquet Bound States in the Continuum (BICs). These findings provide new avenues for engineering controllable quantum transport and localized states in ultracold atom experiments.
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Mesoscale and Nanoscale Physics

Giant Nonlinear Photon-Drag Currents in Moiré Bilayers

Zhuocheng Lu, Zhuang Qian, Zhichao Guo et al. (+4 more)

The bulk photovoltaic effect provides a fundamental pathway for direct light-to-current conversion in quantum materials. However, these nonlinear currents are often strictly constrained or forbidden by crystal symmetries, hindering their exploration in a broader range of materials. While the nonlinear photon-drag effect leverages finite photon momentum to circumvent these constraints, its investigation has been largely confined to toy models, lacking a robust numerical framework for realistic materials. Here, we develop a unified microscopic theory of nonlinear photon-drag currents formulated within a geometric-loop framework, providing both a transparent quantum-geometric interpretation and numerical tractability. Applying this formalism to twisted bilayer graphene (TBG), we demonstrate that a finite, in-plane photon momentum can trigger massive nonlinear responses, rivaling the giant photovoltaic currents reported in typical 2D materials. These currents exhibit high tunability via photon wavevector, twist angle, and light polarization. Our work not only provides a generalized framework for momentum-dependent light-matter interactions but also establishes the nonlinear photon-drag effect as a potent mechanism for unlocking unprecedented optoelectronic functionalities beyond the limitations of the conventional bulk photovoltaic effect.
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All authors Zhuocheng Lu, Zhuang Qian, Zhichao Guo, Likun Shi, Shi Liu, Hua Wang, Kai Chang

Soft Condensed Matter · Cross-listed from physics.chem-ph

Quantum Jump Approach for Photosynthetic Energy Transfer with Chemical Reaction and Fluorescence Loss

Rui Li, Yi Li, Kai-Ya Zhang et al. (+1 more)

Recently, the coherent modified Redfield theory (CMRT) has been widely used to simulate the excitation-energy-transfer (EET) processes in photosynthetic systems. However, the numerical simulation of the CMRT is computationally expensive when dealing with large-scale systems, e.g. photosystem I (PSI) and II (PSII). On the other hand, the chemical reaction and fluorescence loss traditionally treated by the non-Hermitian Hamiltonian approach may result in significantly error in a wide range of parameters. To address these issues, we introduce a quantum jump approach (QJA) based on the CMRT to simulate the evolution of photosynthetic complexes including both the chemical reaction and fluorescence loss. The QJA shows higher accuracy and efficiency in simulating the EET processes. The QJA-CMRT approach may provide a powerful tool to design and optimize artificial photosynthetic systems, which benefits future innovation in the field of energy.
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All authors Rui Li, Yi Li, Kai-Ya Zhang, Qing Ai

Mesoscale and Nanoscale Physics

Cusped Electrical Conductivity in Spin-1 Chiral Fermion Systems Arising from Multifold Band Degeneracy

Risako Kikuchi, Junya Endo and Ai Yamakage

The energy-dependent electrical conductivity in spin-1 chiral fermion systems with disorder is studied using the self-consistent Born approximation. A distinct cusp-like feature appears at an energy different from the band-crossing point, arising from the multifold band-crossing structure formed by the Dirac and trivial bands. The energy position of the cusp and the corresponding value of the electrical conductivity are found to depend sensitively on both the impurity scattering strength and the curvature of the trivial band. These findings demonstrate the critical role of multifold band crossings and disorder-induced broadening of energy levels in determining the transport properties, offering theoretical insight into the unconventional conductivity behavior observed in topological semimetals hosting spin-1 chiral fermions.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph

Spectroscopy on a single nonlinear mode recognizes quantum states

Wouter Verstraelen, Stanisław Świerczewski, Andrzej Opala et al. (+7 more)

Characterising optical quantum states is essential for the development of quantum technologies. While traditional approaches to perform full quantum state tomography are often experimentally demanding, neuromorphic architectures may provide an effective alternative. In this work, we demonstrate how a quantum nonlinear driven-dissipative mode is sufficient to act as a quantum reservoir. By analyzing the occupations at different frequencies in the emission spectrum, a linear regression suffices in many cases to recognize the relevant parameters of incident squeezed states. Beyond highlighting the general potential of this approach under continuous driving, we illustrate its effectiveness in an explicit nontrivial example where the source is a degenerate optical parametric oscillator (OPO), coupled to a nonlinear polariton microcavity.
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All authors Wouter Verstraelen, Stanisław Świerczewski, Andrzej Opala, Andrew Haky, Matteo Gadani, Huawen Xu, Oleksandr Kyriienko, Michał Matuszewski, Alberto Bramati, Timothy C.H. Liew

Materials Science

Energy-Dependent Magnetic Modifications in HOPG via Microbeam Scanning

Ram Kumar, Aditya H. Kelkar, Neeraj Shukla et al. (+2 more)

Medium-energy ion irradiation is a promising technique for inducing magnetism in materials with partially filled d or f electron bands. This approach enables precise control over the density and spatial distribution of irradiation-induced defects, which play a crucial role in modifying the electronic and magnetic properties of the system. The primary objective of this experiment was to investigate the influence of ion energy variation on the magnetic properties of highly oriented pyrolytic graphite (HOPG). To achieve this, HOPG samples were irradiated with protons 1-3 MeV and carbon ions 600 keV - 2 MeV. A significant change in the magnetic moment was observed with respect to the irradiation energy for both ion species. The effect of energy variation was analyzed using a vibrating sample magnetometer (VSM) and SRIM simulations. The results demonstrate that ion-beam-induced magnetic ordering strongly depends on both the ion species and the beam energy. Magnetic measurements were performed with varying irradiation energies, showing that carbon ion irradiation produces a higher degree of magnetic ordering compared to proton irradiation at the same dose. The maximum magnetization was obtained at 1.2 MeV carbon ion irradiation. SRIM simulations confirm that carbon ions create a greater number of lattice defects than proton ions, which correlates with the enhanced magnetic response.
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All authors Ram Kumar, Aditya H. Kelkar, Neeraj Shukla, Paras Poswal, Sheshmani Singh

Materials Science

Accelerated Materials Discovery through Cost-Aware Bayesian Optimization of Real-World Indentation Workflows

Vivek Chawla, Stephen Puplampu, Haochen Zhu et al. (+3 more)

Accelerating the discovery of mechanical properties in combinatorial materials requires autonomous experimentation that accounts for both instrument behavior and experimental cost. Here, an automated nanoindentation (AE-NI) framework is developed and validated for adaptive mechanical mapping of combinatorial thin-film libraries. The method integrates heteroskedastic Gaussian-process modeling with cost-aware Bayesian optimization to dynamically select indentation locations and hold times, minimizing total testing time while preserving measurement accuracy. A detailed emulator and cost model capture the intrinsic penalties associated with lateral motion, drift stabilization, and reconfiguration-factors often neglected in conventional active-learning approaches. To prevent kernel-length-scale collapse caused by disparate time scales, a hierarchical meta-testing workflow combining local grid and global exploration is introduced. Implementation of the workflow is shown on a experimental Ta-Ti-Hf-Zr thin-film library. The proposed framework achieves nearly a thirty-fold improvement in property-mapping efficiency relative to grid-based indentation, demonstrating that incorporating cost and drift models into probabilistic planning substantially improves performance. This study establishes a generalizable strategy for optimizing experimental workflows in autonomous materials characterization and can be extended to other high-precision, drift-limited instruments.
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All authors Vivek Chawla, Stephen Puplampu, Haochen Zhu, Philip D. Rack, Dayakar Penumadu, Sergei Kalinin

Materials Science · Cross-listed from physics.optics

Broadband telecom single-photon emissions from InAs/InP quantum dots grown by MOVPE droplet epitaxy

Shichen Zhang, Li Liu, Kai Guo et al. (+6 more)

The development of quantum materials for single-photon emission is crucial for the advancement of quantum information technology. Although significant advancement has been witnessed in recent years for single photon sources in near infrared band ({\lambda}~700-1000 nm), several challenges have yet to be addressed for ideal single photon emission at the telecommunication band. In this study, we present a droplet-epitaxy strategy for O-band to C-band single-photon source based semiconductor quantum dots (QDs) using metal-organic vapor-phase epitaxy (MOVPE). Via investigating the growth conditions of the epitaxial process, we have successfully synthesized InAs/InP QDs with narrow emission lines spanning a broad spectral range of {\lambda}~1200-1600 nm. The morphological and optical properties of the samples were characterized using atomic force microscopy and micro photoluminescence spectroscopy. The recorded single-photon purity of a plain QD structure reaches (g(2)(0) = 0.16), with a radiative recombination lifetime as short as 1.5 ns. This work provides a crucial platform for future research on integrated microcavity enhancement techniques and coupled QDs with other quantum photonics in the telecom bands, offering significant prospects for quantum network applications.
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All authors Shichen Zhang, Li Liu, Kai Guo, Xingli Mu, Yuanfei Gao, Junqi Liu, Fengqi Liu, Quanyong Lu, Zhiliang Yuan

Soft Condensed Matter

Computer Simulation of Gel Formation in Colloidal Systems of Sticky Rods

Johannes Krotz

We develop and validate a simulation framework for colloidal gelation. We first reproduce the benchmark results of Santos, Campanella, and Carignano for spherical, gel-forming particles, then extend the methodology to more complex systems of “sticky” spherocylindrical rods interacting via a Kihara-like potential. Using comprehensive parameter sweeps documented for reproducibility, we analyze the emergence of porous, percolating networks and conduct a topological characterization of the resulting microstructures. This characterization leverages Early TDA to extract multiscale connectivity features and to define topology-driven metrics for automated comparison between simulations and experiments. Our simulations reveal a clear dependence of network formation on rod aspect ratio and particle density, consistent with established theory and, to our knowledge, not previously demonstrated for spherocylindrical colloids with Kihara-type interactions. Rheological probing of the simulated systems shows signatures characteristic of gels, which supports the structural analysis. We further compare our computational results with experimental data obtained on Bastian Trepka's gels collected by Jacob Steindl. Although these first comparisons indicate that the present model is not yet sufficient to quantitatively describe those specific gelled systems, the agreement in qualitative trends and the robustness of our tools suggest strong potential. Overall, the work demonstrates functional, extensible methods for simulating gelation in rod-based colloids, provides topological data analysis based metrics that can aid automated comparison between experiments and simulations, and outlines several promising directions for future refinement and application.
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Thursday 20 November

Mesoscale and Nanoscale Physics · Cross-listed from physics.chem-ph

Electric-Field-Induced Tautomerism in Metal-Free Benziporphyrins Enables Aromaticity-Controlled Conductance Switching

Yenni P. Ortiz, Arnau Cortés-Llamas, Jordi Ribas-Arino et al. (+1 more)

Metal-free porphyrins can switch between hydrogen-bonded tautomers, potentially enabling reversible control in molecular electronics. However, electric field gating of porphyrin tautomerism, which is critical for device integration, has not been fully realized. We propose metal-free benziporphyrins (MFBPs), in which one pyrrole ring is replaced with a phenol group, as a new platform for tautomer-based molecular electronics. This approach introduces asymmetry, which allows for three distinct tautomers, each possessing a characteristic aromatic or antiaromatic electronic structure. Density functional theory and quantum transport calculations show that: i) experimentally realisable electric fields can selectively stabilize each tautomer, and ii) each tautomer exhibits a characteristic conductance profile. The strong switching capability of MFBPs is demonstrated by ON/OFF ratios exceeding 500 at low bias. Fused MFBPs further expand functionality by providing multiple tautomeric states for multistate molecular registers and enabling wire-like architectures with enhanced conductance. These results establish MFBPs as versatile building blocks for electric-field-responsive molecular devices and open new research opportunities for molecular-scale logic and memory.
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All authors Yenni P. Ortiz, Arnau Cortés-Llamas, Jordi Ribas-Arino, Stefan T. Bromley

Mesoscale and Nanoscale Physics

Floquet-engineered Valley Topology with Anisotropic Response in 1T'-WSe$_2$ and Janus WSeTe monolayers

Zhe Li, Haijun Cao, Lijuan Li et al. (+3 more)

Valley topology has emerged as a key concept for realizing new classes of quantum states. Here, we investigate Floquet-engineered topological phase transitions in anisotropic 1T'-WSe$_2$ and its Janus derivative WSeTe monolayers, which exhibit valley-degenerate and valley-polarized characteristics, respectively. In 1T'-WSe$_2$, a single topological-phase-transition (TPT) occurs from the quantum-spin-Hall state (QSH) to the quantum anomalous Hall (QAH) state, involving one spin channel at both valleys simultaneously. In contrast, Janus WSeTe undergoes a two-stage Floquet-driven TPT that occurs within a single valley and sequentially involves two spin components. The intermediate phase manifests as a valley-polarized QAH (vp-QAH) state with a finite valley Chern number, while the final phase evolves into a high-Chern-number QAH state with distinct valley gaps. Furthermore, an in-plane anisotropic response of the TPTs is predicted under oblique light incidence, reflecting the intrinsic low-symmetry nature of the lattice. These findings provide a comprehensive understanding of Floquet-engineered valley-based topological properties and offer guidance for designing light-controllable valleytronic and topological devices.
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All authors Zhe Li, Haijun Cao, Lijuan Li, Huixia Fu, Mengxue Guan, Sheng Meng

Statistical Mechanics

Zero-temperature dynamics of the spherical model with non-reciprocal interactions

Daniel A. Stariolo and Fernando L. Metz

We analytically solve the zero-temperature dynamics of the spherical model with non-reciprocal random interactions drawn from the real elliptic ensemble of random matrices, where a single parameter $\eta$ continuously interpolates between purely symmetric ($\eta=1$) and purely antisymmetric ($\eta=-1$) couplings. We show that the two-time correlation and response functions depend on both times in the presence of non-reciprocal interactions, reflecting the breakdown of time-translation invariance and the absence of equilibrium at long times. Nevertheless, the long-time relaxation of the two-time observables is governed by exponential decays, in contrast to the slow, power-law relaxation characteristic of the model with purely symmetric interactions. We further show that, when the interactions present antisymmetric correlations of strength $\eta <0$, there is a time scale $\tau(\eta)$ above which the dynamics undergoes a transition to an oscillatory regime where the two-time observables display periodic oscillations with an exponentially decaying amplitude. Overall, our results give a detailed account of the dynamics of the spherical model with non-reciprocal interactions at zero temperature, providing a benchmark for the study of complex systems with nonlinear and asymmetric interactions.
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Soft Condensed Matter

Glassy polymers' strain-hardening moduli scale with their statistical-segment volumes

Robert S. Hoy

Using molecular dynamics simulations, we show that a widely-accepted theoretical prediction for glassy-polymeric strain hardening moduli ($G_R \propto \rho_e$, where $\rho_e$ is the entanglement density) fails badly for semiflexible polymers with $N_e \lesssim 4C_\infty$. By postulating that the length, energy and strain scales controlling $G_R$ are the Kuhn length $\ell_K$ and statistical segment length $b = \sqrt{\ell_0 \ell_K}$ (where $\ell_0$ is the backbone bond length), the intermonomer binding energy $u_0$, and the incremental elastic strain $S_{\rm c}$ required to activate Kuhn-segment-scale plastic rearrangements, we develop a scaling theory predicting that $G_R = S_{\rm c}(u_0/\ell_0^3) b^3$ in the athermal limit. This prediction agrees quantitatively (semi-quantitatively) with simulated $G_R$ values for both flexible and semiflexible polymer glasses subjected to athermal uniaxial-stress extension (constant-volume simple shear), over a range of $\ell_K/\ell_0$ that is wider than that spanned by real systems.
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Strongly Correlated Electrons

Breakdown of adiabaticity in topological quantum liquids

Carola Ciaramelletti, Daniel Arrufat-Vicente, Simone Paganelli et al. (+1 more)

We study the temporal behavior of topological quantum fluids with strong long-range couplings under slow external perturbations, whose rate $\delta$ approaches the quasi-static limit $\delta\to 0$. As expected, due to strong long-range interactions, the system lies in the mean-field universality and the density of defects for drives across the quantum critical point is adiabatic $n_{\rm exc}\propto \delta^{2}$. However, if the drive is instead terminated precisely at the edge of the topological non-trivial phase, the number of generated excitations becomes extensive $n_{\rm exc}\propto O(1)$. This result fundamentally breaks the established universal behavior observed in local topological quantum fluids and demonstrates a novel mechanism for the breakdown of adiabaticity in fermionic systems with strong long-range interactions.
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All authors Carola Ciaramelletti, Daniel Arrufat-Vicente, Simone Paganelli, Nicolo Defenu

Materials Science

Magnetic Properties of the Quasi-1D Magnesium Lanthanide Borates Mg$Ln$B$_5$O$_{10}$

Lachlan G. M. Rooney, Siân E. Dutton and Nicola D. Kelly

Lanthanide borates are widely studied for their optical and magnetic properties. A wide variety of structures are known with 3, 2, 1 and 0 dimensional connectivity of lanthanide ions. Here, we explore Mg$Ln$B$_5$O$_{10}$, with a quasi-1D arrangement of the $Ln$ ions. Polycrystalline samples of Mg$Ln$B$_5$O$_{10}$ ($Ln$ = La, Pr, Nd, Sm–Er) were synthesised with high purity via a sol-gel method. Powder X-ray diffraction data confirmed the reported monoclinic space group ($P2_1/c$). The magnetic $Ln^{3+}$ ions in Mg$Ln$B$_5$O$_{10}$ form relatively isolated zig-zag chains parallel to the $b$ axis. Magnetic susceptibility and isothermal magnetisation were measured: all samples except $Ln=$ (Eu, Sm) fit the Curie-Weiss Law in isothermal magnetisation at high temperatures, in broad agreement with theoretical expectations. $Ln =$ (Nd, Tb, Dy, Ho) exhibit signatures characteristic of Ising spin saturation, implying single ion anisotropy, while Gd exhibits characteristics of Heisenberg spins. Estimation of magnetic interactions suggests that Mg$Ln$B$_5$O$_{10}$ are candidate materials for quasi-1D magnetism. The magnetocaloric entropy change was also calculated, with MgGdB$_5$O$_{10}$ showing promise for application to solid-state refrigeration at liquid helium temperatures.
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Other Condensed Matter

Reentrant Landau Levels in a Dirac topological insulator

C. Kaufmann Ribeiro, J. C. Mutch, Q. Jiang et al. (+13 more)

The quantum limit, where magnetic fields confine carriers to the lowest Landau level, is predicted to host exotic quantum phases arising from strengthened electronic correlations, reduced dimensionality, and increased degeneracy. We report a novel quantization regime realized in the ultra-quantum limit of the narrow-gap Dirac insulator ZrTe5, marked by anomalous magnetoresistance oscillations. These oscillations, measured in ZrTe5 single crystals down to 700 mK and up to 60 T, are distinctly non-1/B periodic and persist for magnetic fields well beyond the quantum limit. In this regime, the competition between Zeeman and cyclotron energies drives a nonlinear evolution and back-bending of Landau levels, causing low-index levels to re-cross the Fermi energy at high fields. This mechanism departs from the standard Lifshitz-Kosevich description and provides a framework to describe how the electronic structure in topological Dirac insulators evolves beyond the quantum limit.
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All authors C. Kaufmann Ribeiro, J. C. Mutch, Q. Jiang, J. P. Ayres-Sims, K. Rubi, C. A. Mizzi, E. A. Peterson, D. Bulmash, J. Singleton, N. Harrison, P. F. S. Rosa, J.-X. Zhu, J.-H. Chu, J. Larrea Jimenez, S. M. Thomas, J. C. Palmstrom

Materials Science

A Constraint-Modulated Rate Law for Glass-Forming Systems: Viscosity Evidence and Dielectric Transfer in Salol

Debra S. Gavant and Christian E. Precker

The viscosity of a glass-forming liquid can increase by more than 14 decades as structural mobility diminishes upon cooling. Continuous Present Actualization (CPA) treats physical change as an ongoing process under the physical conditions currently in force. CPA plus constraint (CPA+C) tests the material hypothesis that relational constraints modulate the observable rate of structural reconfiguration. The bounded function $C(T)$ supplies an operational temperature modulation for this proposed influence. The five-parameter law is compared with the VFT, MYEGA, and Avramov–Milchev equations using source-verified data. For 35 published salol viscosity symbols spanning 14.15 decades, CPA+C is favored over the nearest comparator by 47.72 Akaike information criterion (AIC) units and reduces the leave-one-symbol-out root-mean-square prediction error from 0.398 to 0.207. It is selected in all 1,000 symbol-level bootstrap resamples under AIC, its small-sample correction (AICc), and the Bayesian information criterion (BIC). For 60 source-verified B$_2$O$_3$ viscosity measurements, CPA+C has a 57.39-unit AIC advantage over the nearest comparator. Salol provides the prospectively identified cross-observable test. The viscosity fit fixes both temperature coordinates and the complete temperature dependence of the viscosity-derived modulation before the dielectric comparison; only dielectric-specific coefficients are fitted. This fixed-geometry model improves on a denominator-matched control by 16.32 AIC units, with AIC preference across all 1,000 propagated viscosity geometries. The viscosity-derived modulation therefore retains predictive information for molecular reorientation in the same liquid. Together, the salol and B$_2$O$_3$ viscosity results and the salol transfer establish a reproducible constraint-modulated rate signature consistent with progressive narrowing of configurational access.
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2511.16791 · 20 Nov · 18 pages, 6 figures. Substantially revised and expanded. Salol now uses 35 published symbols as inferential units; B2O3 was source-verified; earlier OTP comparisons are no longer primary evidence. Independently validated salol dielectric and viscosity-to-dielectric transfer analyses added. Data/code: https://doi.org/10.5281/zenodo.22306850

Abstract PDF $LIQD ×2$BAYS ×1

Statistical Mechanics · Cross-listed from math-ph

A permutation-based power series representation of the Baker-Campbell-Hausdorff formula

Joseph M. Jones and M. W. Long

The Baker-Campbell-Hausdorff formula was recently resummed exactly in one variable, and left as a power series in the other (Moodie and Long 2021 J. Phys. A: Math. Theor. 54 015208). The coefficients of the power series were provided as a sum of products of three hyperbolic functions that are analogous to the familiar commutator expansion. We find a new form of the power series coefficients that is a linear combination of just one of the hyperbolic functions. This linear combination can be understood through elementary permutations of the arguments of the hyperbolic function. We use generating functions and hyperbolic identities to relate the representations. The permutation representation is radically different to previously known structures in the Baker-Campbell-Hausdorff formula and naturally supersedes the previous power series representation for future use, in our opinion. It also allows us to prove a set of intriguing marching identities that are useful in physical applications and were discovered in the initial work.
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Mesoscale and Nanoscale Physics

Fabrication of A Dual Gated Mirror Symmetric Twisted Trilayer Graphene Device to Study Superconductivity

Ahmed Shaikh, Phanibhusan Singha Mahapatra and Eva Y. Andrei

Though research on graphene by itself has waned, the interest in moire materials, materials made with stacked layers of graphene with a rotational twist between the layers, has exploded in popularity. These layered devices show a key feature, flat bands. Flat bands localize electrons, which in turn leads to the expression of correlated states such as Mott insulators, superconductivity, and more. A key property of these devices is that their 2D nature allows us to tune them in situ, effectively allowing us to change the device's electronic properties. This powerful ability greatly reduces the time and money required to study superconductivity. The superconductivity in these systems seems to be similar to high-temperature superconductors such as cuprates, giving us a path towards studying high-temperature superconductivity. The fabrication of these devices is nontrivial, and thus we detail one general way to create these layered devices to give maximal tunability.
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Materials Science

Light-Induced Lattice Coherence and Emission Enhancement in PTM-Passivated CsSnI3 Perovskites

Thomas Y. Adams, Bruce Barrios, Michael Ziegenfus et al. (+2 more)

Metal halide perovskites continue to lead in optoelectronic applications, but the toxicity of lead has driven efforts to identify environmentally benign alternatives. Cesium tin iodide is one such, with a direct bandgap and near-infrared emission, though its performance is limited by instability. We show that phthalimide (PTM) passivation during single crystal growth enhances optical output and ambient stability. Under continuous excitation, PTM-passivated microscale crystals show up to a nearly one order of magnitude increase in photoluminescence (PL) quantum yield, accompanied by reversible sharpening of a low-frequency Raman mode associated with Cs rattling. This reveals dynamic, light-induced lattice reordering that passivates trap states and enhances radiative recombination. Mechanical grinding yields nanocrystals with redshifted, narrowed PL, consistent with a relaxed polymorph and reduced inhomogeneous broadening. Despite increased surface area, PTM remains effective in preserving near-infrared emission in nanocrystals as well. Power-dependent PL reveals distinct carrier dynamics, where microcrystals show redshift due to bandgap renormalization, while nanocrystals show blueshift and elevated carrier temperatures (300 to 1900 K), consistent with hot-carrier recombination. Extended illumination reveals reversible optical changes, including PL modulation, reflecting dynamic light-matter interactions and evolving defect landscapes. These results identify PTM-passivated Cesium tin iodide as an ideal platform for probing morphology-dependent carrier relaxation and light-induced vibrational coherence in lead-free perovskites.
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All authors Thomas Y. Adams, Bruce Barrios, Michael Ziegenfus, Hui Cai, Sayantani Ghosh

Materials Science

Tungsten doping-induced phase transition in CVD-grown MoS2 bilayers

Ana Senkić, Rachael Keneipp, Petra Ivatović et al. (+5 more)

Controlling the crystal phase of two-dimensional (2D) transition metal dichalcogenides (TMDs) is essential for tailoring their optical and electronic properties. While phase transitions in monolayer TMDs and semiconductor-to-metal conversions have been widely studied, structural transitions between semiconducting polytypes - particularly in bilayer (2L) systems - remain underexplored. Here, we demonstrate a W doping-induced phase transition from non-centrosymmetric AA stacking to centrosymmetric AB' in 2L MoS2 synthesized by chemical vapor deposition (CVD). Using polarization-resolved second harmonic generation (SHG) and low-frequency Raman spectroscopy, we identify a phase transition correlated with increasing tungsten (W) concentration. The dilute W-doped 2L system exhibits a vanishing SHG signal and a stiffening of the layer-breathing (LB) vibrational mode, in contrast to undoped samples with strong SHG and a softer LB mode. Aberration corrected scanning transmission electron microscopy (AC-STEM) demonstrates the spatial distribution of W concentration and associated structural changes. These findings highlight W-doping as an effective strategy for inducing phase transitions in 2L TMDs, opening new possibilities for engineered heterostructures, phase-controlled device applications or as a source of single photon emitters.
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All authors Ana Senkić, Rachael Keneipp, Petra Ivatović, Namrata Pradeep, Vincent Meunier, Marko Kralj, Marija Drndić, Nataša Vujičić

Materials Science

Landau-Lifshitz-Bloch simulations of the magnetocaloric effect in continuous ferromagnetic-paramagnetic transitions

Luis M. Moreno-Ramírez, Luis Sánchez-Tejerina, Óscar Alejos et al. (+2 more)

The usefulness of modeling magnetocaloric materials expands from the understanding of their behavior to the prediction of new materials, playing a fundamental role in the optimization of their performance. In contrast with other areas of magnetic materials research, micromagnetic simulations of magnetocaloric materials are scarce due to the difficulty of modeling the material in the vicinity of the transition. To solve this limitation, we propose the use of micromagnetic simulations based on the Landau-Lifshitz-Bloch equation to study the magnetocaloric effect of a ferromagnetic material around its Curie transition. Following our proposed methodology, we obtain reliable isothermal entropy change curves for both monocrystalline and polycrystalline configurations, where we consider different anisotropic contributions. The robustness of the method was evaluated, yielding results that agreed with previous experimental and theoretical observations. Our study shows that micromagnetic simulations are a powerful tool for analyzing magnetocaloric materials with complex microstructures.
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All authors Luis M. Moreno-Ramírez, Luis Sánchez-Tejerina, Óscar Alejos, Victorino Franco, Víctor Raposo

Strongly Correlated Electrons

Excited states from local effective Hamiltonians of matrix product states and their entanglement spectrum transition

Denise Cocchiarella, Mingru Yang, Yueshui Zhang et al. (+3 more)

Solving excited states is a challenging task for interacting systems. For one-dimensional critical systems, however, excited states can be directly accessed from the eigenvectors of the local effective Hamiltonian that is constructed from the ground state obtained by variational matrix product state (MPS) optimization. Despite its numerical success, the theoretical mechanism underlying this method has remained largely unexplored. In this work, we provide a conformal field theory (CFT) perspective that helps elucidate this connection. The key insight is that this construction effectively uses a truncated basis of ground-state Schmidt vectors to represent excited states, where the contribution of each Schmidt vector can be expressed as a CFT correlation function and shown to decay with increasing Schmidt index. The CFT analysis further predicts an entanglement-spectrum transition of excited states as the ratio of the subsystem size to the total system size is varied. Our numerical results support this picture and demonstrate a reorganization of the entanglement spectrum into distinct conformal towers as this ratio changes.
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All authors Denise Cocchiarella, Mingru Yang, Yueshui Zhang, Mari Carmen Bañuls, Hong-Hao Tu, Yuhan Liu

Mesoscale and Nanoscale Physics

Liouvillian topology and nonreciprocal dynamics in open Floquet chains

Florian Koch, Yu-Min Hu and Jan Carl Budich

Open quantum systems far from thermal equilibrium can exhibit remarkable physical phenomena including topological properties without a direct equilibrium counterpart. Along these lines, in periodically driven-dissipative systems within the effective non-Hermitian (NH) Hamiltonian approximation spectral winding numbers have been linked to intriguing nonreciprocal transport properties. Here, going beyond an NH Hamiltonian description, we introduce and study a microscopic lattice model of a driven open quantum system described by a Markovian quantum master equation, which exhibits the mentioned spectral winding within an NH approximation. By encompassing quantum jump processes in the topological analysis, we uncover a distinct jump-induced topological phase, which qualitatively corresponds to the richer nonreciprocal transport properties of the fully quantum model. In addition, we find that the NH skin effect, i.e., the accumulation of a macroscopic number of eigenstates at one end of the system, is already visible in the transient dynamics even for systems with periodic boundary conditions. Our results exemplify the subtle correspondence between NH topological properties and physical manifestations of Liouvillian topological properties in open quantum systems, thus providing a theoretical framework towards understanding unidirectional transport in quantum dissipative Floquet dynamics.
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Statistical Mechanics · Cross-listed from hep-th

EFT meets CFT: Multiloop renormalization of higher-dimensional operators in general $\phi^4$ theories

Johan Henriksson, Stefanos R. Kousvos and Jasper Roosmale Nepveu

The renormalization of composite operators is a fundamental aspect of quantum field theory, relevant for the description of phase transitions and high energy phenomenology. We calculate the anomalous dimensions of a large set of operators in any scalar $\phi^4$ theory in $d=4-\varepsilon$ dimensions, up to five loops in most cases. The results have applications in both effective field theory (EFT) and conformal field theory (CFT). As an EFT application, we extract the five-loop renormalization group (RG) equations of the Higgs sector of the Standard Model EFT at dimension six, and up to two loops at dimension eight, aligning our operator basis with custodial symmetry violation. Additionally, for CFT, by resumming the $\varepsilon$-expanded results at the fixed-point, we determine the entire low-lying spectrum (i.e. up to dimension six and Lorentz rank two) of the Ising, $O(n)$ and hypercubic scalar CFTs. Our work enables future conformal bootstrap studies for numerous theories of interest. We include introductions to EFT and CFT, and we illustrate our method and the structure in RG mixing matrices in several illuminating examples, which may also be of general interest. All results in the general theory are publicly available and we describe a systematic path towards applying them to more complicated CFTs.
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