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Physics Condensed Matter

cond-mat Watch Condensed Matter

Thursday 22 January

Materials Science · Cross-listed from hep-ex

Muon beams towards muonium physics: progress and prospects

Siyuan Chen, Mingchen Sun and Jian Tang

Advances in accelerator technology have led to significant improvements in the quality of muon beams over the past decades. Investigations of the muon and muonium enable precise measurements of fundamental constants, as well as searches for new physics beyond the Standard Model. Furthermore, by utilizing muon beams with high intensity and polarization, studies of the dynamics of the muon and muonium within atomic level can offer valuable insights into materials science. This review presents recent progress and prospects at the frontiers of muon beams and high-precision muonium physics. It also provides an overview of novel methods and detection techniques to achieve high sensitivities in different areas, including particle physics, nuclear physics, materials science and beyond.
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Materials Science

Bias-triggered conductivity relaxation (BCR): a unique tool to simultaneously investigate thermodynamics, kinetics and electrostatic effects of oxygen reactions in MIEC thin films

Alexander Stangl, Alexander Schmid, Adeel Riaz et al. (+2 more)

Mixed ionic electronic transfer (MIET) reactions, such as the oxygen reduction reaction (ORR) at oxide surfaces, are of paramount importance to manifold technologically highly relevant processes and fundamental understanding must be developed to improve performance and tailor highly efficient electrodes and catalysts. Understanding such complex multi-step reactions, requires the study of kinetic processes, underlying thermodynamic properties, i.e. ionic and electronic defect concentrations and electrostatic surface effects. However conventional techniques struggle to uncover the complete picture within the same sample/measurement. Here, we overcome this limitation by introducing bias-triggered conductivity relaxation (BCR) as a novel tool to investigate MIET reactions on oxides. It is based on alternating out-of-plane coulometric titration/polarization and in-plane electrical conductivity relaxation measurements, providing simultaneous electronic, ionic and extraordinarily rich surface kinetics information. This innovative combination of electrical and chemical driving forces synergizes information depth, with enhanced time resolution, versatility and speed, yet it lifts the weaknesses of the individual approaches, while remaining cost-effective and surprisingly simple. Furthermore, BCR allows to disentangle overpotential induced electrostatic modifications of the surface kinetics in a unique manner. We showcase the advantages of BCR in this work by studying the ORR in model (La,Sr)FeO$_{3-{\delta}}$ thin film electrodes and reporting on their thermodynamic and kinetic properties.
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All authors Alexander Stangl, Alexander Schmid, Adeel Riaz, Jürgen Fleig, Arnaud Badel

Disordered Systems and Neural Networks

Structural constraints on mobility edges in one-dimensional quasiperiodic systems

Sanghoon Lee, Tilen Cadez and Kyoung-Min Kim

Mobility edges commonly arise in one-dimensional quasiperiodic systems once exact self-duality is broken, yet their origin is typically understood only at the level of individual Hamiltonians. Here we show that mobility edge positions are not independent spectral features of individual Hamiltonians, but are structurally constrained across quasiperiodic Hamiltonians related by an isospectral duality. Using a bichromatic Aubry–André model as a minimal setting, we demonstrate that this constraint is encoded in an exact identity for Lyapunov exponents derived from the Thouless formula. As a consequence, the mobility edge positions are restricted to a reduced set of energies. In the self-dual limit, these mobility edge positions coincide at a single localization–delocalization transition. This structural constraint enforces a linear critical scaling of the physical Lyapunov spectrum near the self-dual point. Numerical results confirm a critical exponent consistent with the standard Aubry–André value of $\nu = 1$, while simultaneously revealing a novel, non-universal energy-dependent prefactor.
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Statistical Mechanics

Mesoscopic Fluctuations in Statistical Systems

V.I. Yukalov and E.P. Yukalova

The fluctuations are termed mesoscopic, when their typical size is essentially larger then the average distance between the nearest neighbors, while being much smaller than the overall system size. Since the features of mesoscopic fluctuations are essentially different from those of the surrounding matter, they can be interpreted as fluctuations of one phase occurring inside another host phase. In condensed matter, these fluctuations are of nanosize. They can occur in many-body systems of different nature, for instance, they are typical for condensed matter, can appear in systems of trapped atoms, and also arise in biological and social systems. A survey of the experimental evidence for the occurrence of mesoscopic fluctuations in different materials and systems is given. The main attention is paid to a general theoretical approach for describing them. Applications of the approach are also discussed.
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Soft Condensed Matter

Inverse Design of Tightly Woven Smart Fabrics

Einav Berin and Hillel Aharoni

We present a geometric framework for the inverse design of smart woven fabrics composed of non-uniformly shrinking threads. A sufficiently tight weaving structure imposes strong local criteria on the material deformation and reduces the local geometry to a single scalar degree of freedom. Control over this degree of freedom can be achieved through simple calibration for each specific material system, via either mechanical experiments or numerical simulations. This reduction allows us to inverse-design a woven smart fabric, that conforms to an arbitrary target geometry when actuated, by solving a nonlinear hyperbolic partial differential equation. We validate this approach by deriving the thread-level actuation required for specific target geometries. We present both exact analytic solutions for symmetric shapes and a numerical optimization method for arbitrary freeform surfaces. These results confirm the practicality of our framework in achieving programmable, complex three-dimensional shaping.
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Materials Science

Graphene-based technologies for energy applications, challenges and perspectives

Etienne Quesnel, Frédéric Roux, Fabrice Emieux et al. (+26 more)

Here we report on technology developments implemented into the Graphene Flagship European project for the integration of graphene and graphene-related materials (GRMs) into energy application devices. Many of the technologies investigated so far aim at producing composite materials associating graphene or GRMs with either metal or semiconducting nanocrystals or other carbon nanostructures (e.g., CNT, graphite). These composites can be used favourably as hydrogen storage materials or solar cell absorbers. They can also provide better performing electrodes for fuel cells, batteries, or supercapacitors. For photovoltaic (PV) electrodes, where thin layers and interface engineering are required, surface technologies are preferred. We are using conventional vacuum processes to integrate graphene as well as radically new approaches based on laser irradiation strategies. For each application, the potential of implemented technologies is then presented on the basis of selected experimental and modelling results. It is shown in particular how some of these technologies can maximize the benefit taken from GRM integration. The technical challenges still to be addressed are highlighted and perspectives derived from the running works emphasized.
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All authors Etienne Quesnel, Frédéric Roux, Fabrice Emieux, Pascal Faucherand, Emmanuel Kymakis, George Volonakis, Feliciano Giustino, Beatriz Martín-García, Iwan Moreels, Selmiye Alkan Gürsel, Ayşe Bayrakçeken Yurtcan, Vito Di Noto, Alexandr Talyzin, Igor Baburin, Diana Tranca, Gotthard Seifert, Luigi Crema, Giorgio Speranza, Valentina Tozzini, Paolo Bondavalli, Grégory Pognon, Cristina Botas, Daniel Carriazo, Gurpreet Singh, Teófilo Rojo, Gunwoo Kim, Wanjing Yu, Clare P Grey, Vittorio Pellegrini

Materials Science

Materealize: a multi-agent deliberation system for end-to-end material design and synthesis

Seongmin Kim, Jaehwan Choi, Kunik Jang et al. (+4 more)

We propose Materealize, a multi-agent system for end-to-end inorganic materials design and synthesis that orchestrates core domain tools spanning structure generation, property prediction, synthesizability prediction, and synthesis planning within a single unified framework. Through a natural-language interface, Materealize enables non-experts to access computational materials workflows and obtain experimentally actionable outputs for material realization. Materealize provides two complementary modes. In instant mode, the system rapidly composes connected tools to solve diverse inorganic tasks-including property-conditioned synthesizable candidate design with synthesis recipes, diagnosis, and redesign of unsynthesizable structures, and synthesizable data augmentation-within a few minutes. In thinking mode, Materealize applies multi-agent debate to deliver more refined and information-rich synthesis recommendations, including reasoning- and model-driven synthesis routes and mechanistic hypotheses. The mechanistic hypotheses are validated by direct comparison with the literature for known mechanisms and further supported by physics-grounded simulations for novel synthesis pathways. By combining tool-level accuracy with reasoning-level integration, Materealize can bridge the gap between computational discovery and practical experimental realization.
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All authors Seongmin Kim, Jaehwan Choi, Kunik Jang, Junkil Park, Varinia Bernales, Alán Aspuru-Guzik, Yousung Jung

Materials Science

Permanent Lattice Compression of Lead-Halide Perovskite for Persistently Enhanced Optoelectronic Properties

Karunakara Moorthy Boopathi, Beatriz Martín-García, Aniruddha Ray et al. (+8 more)

Under mild mechanical pressure, halide perovskites show enhanced optoelectronic properties. However, these improvements are reversible upon decompression, and permanent enhancements have yet to be realized. Here, we report antisolvent-assisted solvent acidolysis crystallization that enables us to prepare methylammonium lead bromide single crystals showing intense emission at all four edges under ultraviolet light excitation. We study structural variations, edge-vs-center, in these crystals using micro-X-ray diffraction and find that the enhanced emission at the edges correlates with lattice compression compared to in the central areas. Time-resolved photoluminescence measurements show much longer-lived photogenerated carriers at the compressed edges, with radiative component lifetimes of ca. 1.4 us, 10 times longer than at the central regions. The properties of the edges are exploited to fabricate planar photodetectors exhibiting detectivities of 3x10^13 Jones, compared to 5x10^12 Jones at the central regions. The enhanced lifetimes and detectivities correlate to the reduced trap state densities and the formation of shallower traps at the edges due to lattice compression.
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All authors Karunakara Moorthy Boopathi, Beatriz Martín-García, Aniruddha Ray, Joao M. Pina, Sergio Marras, Makhsud I. Saidaminov, Francesco Bonaccorso, Francesco Di Stasio, Edward H. Sargent, Liberato Manna, Ahmed L. Abdelhady

Materials Science

Systematic Magnetic Structure Generation Based on Oriented Spin Space Groups: Formulation, Applications, and High-Throughput First-Principles Calculations

Takuya Nomoto, Kohei Shinohara, Hikaru Watanabe et al. (+1 more)

We propose a framework for generating magnetic structures, inspired by the concept of oriented spin space groups (SSGs): magnetic structures are first generated as totally symmetric representations of an SSG and are then rotated such that they belong to the maximal magnetic space group of the SSG, which we term spin-symmetry-adapted (SSA) structures and oriented SSA structures, respectively. This is a natural framework to enforce fixed magnetic moment magnitudes on the symmetry-equivalent sites as well as to exploit the spin-orbit coupling (SOC)-induced hierarchy of energy scales. To examine the present scheme, we analyze the MAGNDATA database and find that 77% of the reported structures are reproducible at the SSG level, among which 82% are fully reproduced within the oriented SSG scheme, regardless of their spin-only group types or propagation vectors. To quantitatively assess computational and predictive performance, we perform spin density functional theory calculations for 283 materials, first carrying out self-consistent calculations for SSA structures without SOC, followed by fixed-charge calculations including SOC for the descendant oriented SSA structures. The experimental magnetic structures are reproduced as energetically most stable in 82% of cases at the SSG level without SOC and in 76% of cases at the oriented SSG level with SOC, showing that the fixed-charge scheme enables accurate evaluation of SOC-induced energy differences at low computational cost. The characteristic energy scale among oriented SSA structures is only $\sim$0.29 meV per magnetic atom, about 300 times smaller than that of distinct SSA structures. These results demonstrate that oriented SSG-based enumeration, combined with the two-step calculations for SSA and oriented SSA structures, provides an efficient and robust route for large-scale magnetic-structure prediction.
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All authors Takuya Nomoto, Kohei Shinohara, Hikaru Watanabe, Ryotaro Arita

Materials Science

Segregation-Controlled Diffusion-Induced Grain Boundary Migration in Alloy 690

Yuntian Jiang, Shuai Zhang, Zhuoming Xie et al. (+4 more)

Grain boundary (GB) migration accompanied by Cr depletion is widely observed in Alloy 690 and is closely linked to intergranular degradation and stress corrosion cracking. However, the fundamental driving force for GB migration and its link with Cr depletion remains unclear. In this work, hybrid molecular dynamics and semi-grand canonical Monte Carlo simulations were employed to investigate GB migration in Alloy 690 under coupled solute diffusion and segregation effects across a range of GB characters. The results show that Cr segregation at GBs, while generally considered favorable for GB stability, can facilitate diffusion-induced GB migration and Cr depletion. Cr diffusion along GBs produces localized Cr depletion zones that are energetically incompatible with positively segregating GBs, generating a chemical driving force that drives GB migration toward the Cr-rich matrix, which ultimately results in persistent GB migration accompanied by a Cr depletion. By quantifying solute-GB interaction energetics, we demonstrate that GB migration is quantitively controlled by the coupled effects of solute diffusivity and segregation strength. These mechanistic insights provide a unified framework that rationalizes experimentally observed correlations between GB character, Cr depletion, and GB migration in Cr-containing alloys.
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All authors Yuntian Jiang, Shuai Zhang, Zhuoming Xie, Xiaohan Bie, Huiqiu Deng, Wangyu Hu, Jie Hou

Strongly Correlated Electrons

Spin reorientations in structurally metastable, disordered, and hexagonal Cr7Te8

K. Guratinder, T.G. Romig, H.C. Mandujano et al. (+2 more)

Vapor deposited two-dimensional Cr$_{7}$Te$_{8}$ displays unusual temperature dependent Hall effect properties, including a room temperature anomalous Hall effect, sign reversals of the Hall resistivity on cooling, and a peak in the Hall resistivity at low temperatures. The two dimensional Cr$_{7}$Te$_{8}$ heterostructures that form the basis of these measurements are hexagonal in structure. We study the magnetic and structural properties of bulk Cr$_{7}$Te$_{8}$ synthesized by quenching from 1000 $^{\circ}$C with the goal of relating the magnetic, structural, and electronic properties. This quenched phase is metastable, hexagonal, and displays different magnetic properties from the slow-cooled and more thermodynamically stable monoclinic phase. High-resolution x-ray diffraction of the quenched hexagonal phase finds a first-order transition to a lower symmetry monoclinic phase on heating above $\sim$ 550 K. Magnetic susceptibility measurements of the quenched hexagonal phase reveal ferromagnetic ordering above room temperature, along with the two distinct transitions at $\sim$ 220~K and $\sim$ 70~K. Through neutron diffraction studies, we find the $\sim$ 220 K anomaly is a spin reorientation transition of the ferromagnetically aligned magnetic moments and the $\sim70$ K feature represents a transition from a high temperature ferromagnet to a low temperature antiferromagnet. We suggest that these magnetic transitions are related to changes in the unit cell dimensions and are connected to the temperature dependent Hall resisitivity studied in two-dimensional heterostructures. This implies a link between structural, magnetic, and electronic properties in the “pseudo" two-dimensional chromium tellurides.
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All authors K. Guratinder, T.G. Romig, H.C. Mandujano, C. Stock, E. E. Rodriguez

Materials Science

Atomic-Scale Insights into Solute Drag Effects on Grain Boundary Motion in Mg-Al and Mg-Ca Alloys

Zhishun Chen, Shudong He, Shuai Zhang et al. (+8 more)

The slip behavior of dislocations and grain boundaries critically governs recrystallization and plastic deformation in Mg alloys and can be strongly influenced by solutes. However, the quantitative effects of solute distribution on defect mobility remain unclear. Using molecular dynamics and Monte Carlo simulations, we systematically investigate how Al and Ca solutes affect the motion of dislocations, low-angle grain boundaries (LAGBs), and high-angle grain boundaries (HAGBs) in Mg. Within the idealized framework of random solid-solution, solute drag is dominated by elastic interactions arising from atomic size mismatch, resulting in a stronger resistance from Ca than from Al. In contrast, under the more realistic condition where solute segregation occurs, the dominant mechanism shifts to chemically driven pinning, whose effectiveness is governed by the attainable segregation density. Owing to strong Ca-Ca repulsion, Al achieves substantially higher segregation concentrations than Ca and therefore exerts much stronger pinning effects. Notably, solute-induced retardation is significantly more pronounced for HAGBs than for LAGBs, leading to amplified solute effects during the late stages of recrystallization, where grain growth is controlled primarily by HAGB migration. These results provide atomic-scale insight into experimentally observed grain refinement in Mg alloys.
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All authors Zhishun Chen, Shudong He, Shuai Zhang, Xiaohan Bie, Zhuoming Xie, Tengfei Yang, Wangyu Hu, Huiqiu Deng, Shiwei Xu, Zhuoran Zeng, Jie Hou

Soft Condensed Matter

Reaction-transport coupling drives spatiotemporal organization in fuel-driven supramolecular polymerization

Akta Singh, Nayana Mukherjee, Jagannath Mondal et al. (+1 more)

Chemically fueled supramolecular systems provide a versatile platform for generating nonequilibrium structures and dynamical instabilities, including chemical oscillations and traveling waves reminiscent of biological organization. However, a minimal mechanistic framework capable of capturing the emergence of such spatiotemporal order is still lacking. Here, we develop a minimal reaction-transport framework for fuel-driven supramolecular polymerization that couples activation-deactivation chemistry with cooperative assembly, fragmentation, and polymer length-dependent diffusion. The model captures autonomous oscillations arising through a Hopf bifurcation and demonstrates how temporal instabilities evolve into spatial self-organization upon inclusion of transport. We show that the nonlinear interplay between reaction kinetics and state-dependent mobility gives rise to traveling polymerization fronts, oscillatory wave dynamics, and complex spatiotemporal patterns. The propagating fronts exhibit near-ballistic dynamics, revealing a fundamentally nonequilibrium transport mechanism emerging from reactive feedback and dynamically evolving diffusivity. These findings establish a minimal physical framework connecting dissipative self-assembly, nonlinear transport, and active matter, while providing design principles for programmable supramolecular materials capable of autonomous spatiotemporal organization.
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All authors Akta Singh, Nayana Mukherjee, Jagannath Mondal, Pushpita Ghosh

Mesoscale and Nanoscale Physics

Supercurrent and multiple Andreev reflections in Ge hut nanowire Josephson Junctions

Han Gao, Jian-Huan Wang, Ji-Yin Wang et al. (+2 more)

We report an experimental study of induced superconductivity in Ge hut nanowire Josephson junctions. The Ge hut nanowires are grown on prepatterned SiGe ridges via molecular beam epitaxy (MBE) and Josephson junction devices are fabricated by contacting the nanowires with Al electrodes. Low-temperature current-bias transport measurements of the Josephson junctions are performed and the measurements show that the devices exhibit gate-tunable supercurrent and excess current. The analysis of excess current indicates that the transparency of the Ge hut nanowire Josephson junctions is as high as 85%. Voltage-bias spectroscopy measurements of the devices show multiple Andreev reflections up to the fourth order. With magnetic field and temperature-dependent measurements of the multiple Andreev reflections, the critical field and the critical temperature of the induced superconductivity in the Josephson junctions are extracted to be ~0.12 T and ~1.4 K. The success in introducing superconductivity into Ge hut nanowires will stimulate their applications in building advanced quantum processors.
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All authors Han Gao, Jian-Huan Wang, Ji-Yin Wang, Jian-Jun Zhang, Hongqi Xu

Mesoscale and Nanoscale Physics

Anomalous valley Hall dynamics of exciton-polaritons

Xingzhou Chen, Yuanjun Guan, Areg Ghazaryan et al. (+6 more)

The valley degree of freedom in atomically thin transition-metal dichalcogenides provides a natural binary index for information processing. Exciton-polaritons formed under strong light-matter coupling offer a promising route to overcome the limited lifetime and transport of bare valley excitons. Here we report an anomalous optical valley Hall effect in a monolayer WS2 exciton-polariton system. Using polarization- and time-resolved real-space imaging, we directly visualize a symmetry-breaking spatial separation of polaritons from opposite valleys under linearly polarized excitation, accompanied by an ultrafast Hall drift velocity on the order of 10^5 m/s. This behaviour cannot be accounted for by conventional cavity-induced mechanisms and instead points to a strain-induced synthetic pseudomagnetic field acting on the excitonic component of polaritons. Our results establish exciton-polaritons as a high-speed and optically accessible platform for valley transport, opening pathways towards tunable valleytronic and topological photonic devices.
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All authors Xingzhou Chen, Yuanjun Guan, Areg Ghazaryan, Shiran Sun, Lingxiao Yu, Ruitao Lv, Artem Volosniev, Zheng Sun, Jian Wu

Mesoscale and Nanoscale Physics

Disparate Quantum Corrections to Conduction in Carbon Nanotube Bundles

Shengjie Yu, Zhengyi Lu, Renjie Luo et al. (+11 more)

Quantum interference effects such as weak localization (WL) and universal conductance fluctuations (UCF) normally yield consistent electronic phase-coherence lengths in homogeneous conductors. Here we show that in individual carbon nanotube bundles exfoliated from highly conductive solution-spun fibers, different probes, including the field scales and magnitudes of WL and UCF and nonlocal magnetoconductance, lead to strikingly disparate estimates of coherence lengths. WL magnetoconductance measured in a perpendicular magnetic field yields a phase-coherence length of approximately 50 nm. In contrast, UCF amplitudes are comparable to e squared over h even for an 8 micrometer long segment, and nonlocal magnetoconductance persists across a 4 micrometer separation of electrodes, revealing phase-coherent transport over micrometer length scales within a single bundle. The coexistence of short- and long-range coherence implies that locally diffusive electrons remain partially phase-correlated among nanotubes within the same bundle. These findings challenge the conventional single-scale picture of mesoscopic coherence and establish carbon nanotube bundles as a model platform for emergent, network-level quantum transport.
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All authors Shengjie Yu, Zhengyi Lu, Renjie Luo, Tanner Legvold, Natsumi Komatsu, Liyang Chen, Oliver S. Dewey, Lauren W. Taylor, Huaijin Sun, Matteo Pasquali, Geoff Wehmeyer, Matthew S. Foster, Junichiro Kono, Douglas Natelson

Mesoscale and Nanoscale Physics · Cross-listed from physics.optics

{\sigma}h-Broken Induced Topological quasi-BIC

Yongqi Chen, Chaofeng Xie, Tongtong Zhu et al. (+2 more)

Transitions from bound states in the continuum (BICs) to quasi-BICs (qBICs) are typically realized by introducing in-plane asymmetry, including permittivity asymmetry ({\epsilon}-qBICs) and geometry asymmetry (g-qBICs). Here, we demonstrate that when the in-plane symmetry is rigorously kept, the transition can also be occurred, provided the out-of-plane asymmetry is designed, which is called {\sigma}h -qBICs in this work. When the {{\sigma}h symmetry is gradually broken, the system undergoes a topological phase transition characterized by a Zak phase inversion, leading to a band inversion between quadrupole and dipole modes. This process not only enables controlled radiation coupling of BICs but also introduces a defect-immune qBIC regime. Our findings establish a general mechanism for engineering high-Q resonances and topologically robust plasmonic cavities.
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All authors Yongqi Chen, Chaofeng Xie, Tongtong Zhu, Weiqiang Ding, Yurui Fang

Materials Science · Cross-listed from physics.optics

An ultrafast diamond nonlinear photonic sensor

Daisuke Sato, Junjie Guo, Takuto Ichikawa et al. (+6 more)

The integration of light and materials technology is key to the creation of innovative sensing technologies. Sensing of electric and magnetic fields, and temperature with high spatio-temporal resolution is a critical task for the development of the next-generation of nanometer-scale quantum devices. Color centers in diamonds are attractive for potential applications owing to their characteristic quantum states, although they require metallic contacts for the introduction of external microwaves. Here, we build an ultrafast diamond nonlinear photonic sensor to assess the surface electric field; an electro-optic sensor based on nitrogen-vacancy centers in a diamond nanotip breaks the spatial-limit of conventional pump-probe techniques. The 10-fs near-infrared optical pulse modulates the surface electric field of a 2D transition metal dichalcogenide and we monitor the dynamics of the local electric field at nanometer-femtosecond spatio-temporal resolutions. Our nanoscopic technique will provide new horizons to the sensing of advanced nano materials.
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All authors Daisuke Sato, Junjie Guo, Takuto Ichikawa, Dwi Prananto, Toshu An, Paul Fons, Shoji Yoshida, Hidemi Shigekawa, Muneaki Hase

Superconductivity

Modulation of superconducting properties by the charge density wave at the surface of 2H-NbSe2

Tetsuo Hanaguri

To investigate the interplay between charge density wave (CDW) and superconductivity, we performed ultralow-temperature spectroscopic-imaging scanning tunneling microscopy on the cleaved surface of the layered superconductor 2H-NbSe2. We found that the superconducting-gap spectrum exhibits intricate structures reflecting the anisotropic gaps opening on multiple Fermi surfaces. Notably, none of the characteristic energy scales apparent in the spectral gap show appreciable spatial variations, suggesting that the finite-momentum pairing is negligible. Instead, the spectral weight near the coherence peak is modulated with the same periodicity as the CDW. The maximum position of the coherence-peak-weight modulation coincides with neither the peak nor the bottom of the CDW modulation; rather, it aligns with the center of one of the two inequivalent triangular plaquettes that comprise the CDW unit cell. This distribution pattern of Bogoliubov quasiparticles directly results from the broken in-plane inversion symmetry at the surface of 2H-NbSe2, which may activate Ising spin-orbit coupling.
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Wednesday 21 January

Materials Science · Cross-listed from physics.chem-ph

Single-run determination of the saturation vapor pressure and enthalpy of vaporization/sublimation of a substance undergoing successive solid-solid and solid-liquid phase transitions: the case of $N$-methyl acetamide

Mohsen Salimi, Aurelien Dantan and Henrik B. Pedersen

We report on the dynamical measurement of the saturation vapor pressure of $N$-methyl acetamide in the temperature range $-30^\circ$C to $34^\circ$C. This is achieved by monitoring the pressure inside a vacuum chamber in which a precooled sample of the substance slowly thermalizes to the chamber temperature, undergoing first a phase transition between two crystalline structures around $1^\circ$C and then a solid-liquid phase transition around $30^\circ$C. Such a measurement provides in a single run accurate data for the saturation vapor pressure and the enthalpies of sublimation and vaporization of the different phases of the investigated substance.
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Materials Science · Cross-listed from physics.chem-ph

Unraveling Surface Chemistry of irreversible reduction of iron oxides through the Time-Resolved APXPS and Chemometrics

Mohammed Alaoui Mansouri, Manoj Ghosalya, Aidin Heidari et al. (+8 more)

This work presents a study on the application of Time-Resolved Ambient Pressure X-ray Photoelectron Spectroscopy (TR-APXPS) in association with chemometric techniques, specifically Principal Component Analysis (PCA) and Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS), to investigate the surface chemistry and dynamics of Fe2O3 reduction processes. The use of TR-APXPS allows for real-time monitoring of chemical changes at the surface of Iron oxides during reduction, providing valuable insights into the reaction mechanisms and kinetics involved. One key challenge in analyzing TR-APXPS data is the presence of overlapping peaks and complex spectral features, which can make accurate quantification and interpretation difficult. Traditional spectral fitting methods may struggle with these complexities and result in ambiguous or inaccurate results. However, the chemometric approaches are promising tools to overcome these challenges by extracting pure spectral profiles of individual chemical species and their temporal profiles from the complex and overlapping data. The results obtained from the TR-APXPS coupled with PCA and MCR-ALS analysis provide a detailed and precise understanding of the surface chemical changes during the Fe2O3 reduction. This includes identifying and following the formation of various intermediate species and their evolution over time, which permits later to establish correlations between surface chemistry and process conditions. The integration of both chemometric tools in TR-APXPS data analysis not only addresses the challenges associated with complex spectral features, but also contributes to a deeper understanding of the underlying chemical changes and their dynamics. The obtained results have significant implications for process optimization, material synthesis, and tailoring of material properties for specific applications.
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All authors Mohammed Alaoui Mansouri, Manoj Ghosalya, Aidin Heidari, Yuzhao Wang, Mourad Kharbach, Anne Hietava, Mikko J. Sillanpää, Ilkka Launonen, Timo Fabritius, Marko Huttula, Samuli Urpelainen

Statistical Mechanics · Cross-listed from quant-ph

Bidirectional teleportation using scrambling dynamics: a practical protocol

Amit Vikram, Edwin Chaparro, Muhammad Miskeen Khan et al. (+3 more)

We show that quantum information scrambling can enable a generic SWAP gate between collective degrees of freedom in systems without universal local control. Our protocol combines a Hayden-Preskill type recovery scheme, associated with the black hole information paradox, with quantum teleportation and runs them in parallel and in opposite directions, enabling bidirectional exchange of quantum states through global interactions alone. This approach cleanly distinguishes the roles of information spreading, entanglement, and chaos for enabling both coherent state transfer and recovery. We propose an experimental realization using the Dicke model, which can be realized in optical cavity and trapped-ion platforms, highlighting the utility of holography in designing practical quantum gates.
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All authors Amit Vikram, Edwin Chaparro, Muhammad Miskeen Khan, Andrew Lucas, Chris Akers, Ana Maria Rey

Materials Science

Scalar and fully relativistic pressure and temperature-dependent ab-initio thermodynamics study of simple cubic polonium

Balaram Thakur, Xuejun Gong and Andrea Dal Corso

The ab-initio thermodynamic properties of simple cubic polonium ({\alpha}-Po) were studied within the quasi-harmonic approximation (QHA), where both lattice vibrations (phonons) and electronic excitations contributions are included in the Helmholtz free energy. We investigate the influence of spin-orbit coupling (SOC) by comparing the scalar relativistic (SR) and fully relativistic (FR) pseudopotentials on the thermodynamic properties of polonium and evaluate the performance of three popular exchange-correlation functionals, GGA (PBE and PBEsol), and LDA (PZ). Temperature and pressure-dependent thermodynamic properties were compared with the available experimental and theoretical studies. We found that the effect of electronic excitations is negligible for all the thermodynamic properties. LDA+SOC provides a better agreement with the experimental volume, while the thermal expansion coefficients from LDA+SOC and PBEsol + SOC closely match experimental values. SOC effects appear insignificant for the isobaric heat capacity but substantially contribute to the adiabatic bulk modulus. The phonon dispersions and mode-Grüneisen parameters ({\gamma}_q{\eta}) were interpolated at the lattice constant corresponding to 301 K. The SR dispersions exhibit several anomalies in all directions, which were suppressed significantly by the inclusion of SOC. The role of SOC on the elastic constant-coefficient (C_ij) and elastic anisotropy factor at 0 K is also studied. The Pugh ratio confirmed that simple cubic polonium is ductile, and we observed that the elastic anisotropy factor and Pugh ratio decreased with increasing pressure. The effect of SOC on the Cauchy pressure is also determined.
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Other Condensed Matter · Cross-listed from physics.optics

Visualization of Gaussian Mode Profile in Gigahertz Surface-Acoustic-Wave Resonators

Shizai Chu, Suraj Thapa Magar, John Nichol et al. (+1 more)

Surface-acoustic-wave (SAW) resonators operating at gigahertz (GHz) frequencies are widely used in wireless telecommunication and quantum information processing. Successful implementation of such resonators calls for detailed microscopic understanding of their mode profiles, energy dissipation channels, and imperfections from microfabrication. In this work, we report on the visualization of acoustic waves in LiNbO3 SAW resonators by transmission-mode microwave impedance microscopy (TMIM). The Gaussian mode profile tightly confined by reflecting mirrors is vividly seen in the TMIM images, from which the linewidth of the resonator itself can be extracted. The spatially resolved acoustic profile also allows us to perform failure analysis on faulty devices. Our work establishes a pathway for further optimization of SAW resonators for classical and quantum acoustic applications.
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All authors Shizai Chu, Suraj Thapa Magar, John Nichol, Keji Lai

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

Interaction between cell membranes and protein inclusions in the large-deformation regime

Gaetano Ferraro and Michele Castellana

Biological membranes are dynamic surfaces whose shape and function are critically influenced by protein inclusions (PIs). While membrane deformations induced by PIs have been extensively studied in the small-deformation regime, a variety of processes involves strong membrane deformations. We investigate the interaction between lipid membranes and PIs in the large deformation (LD) regime, with the finite-element method. We develop an approximate analytical solution that captures key features of the LD regime. We show that the force exerted by the membrane on a PI displays a non-monotonic behavior with respect to the PI vertical displacement. The qualitative features of this force appear to be independent of the protein geometry. For two interacting PIs, the membrane-mediated potential exhibits sub-power-law decay with inter-protein distance, reflecting the complex nature of the elastic medium. The interaction potential shows that conical PIs with identical and opposite orientations repel and attract, respectively, confirming the analogy between PI orientation and electric charge, in the LD regime. In the presence of membrane flows, we identify a characteristic velocity that separates two regimes in which bending rigidity and viscous effects dominate, respectively, implying the onset of flow-induced deformations above such velocity threshold. Overall, our results provide quantitative predictions for membrane-protein systems in biologically relevant scenarios involving LDs, with implications for protein sorting, clustering, and membrane trafficking.
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Statistical Mechanics · Cross-listed from quant-ph

Dissipative Quantum Dynamics in Static Network with Different Topologies

Wei-Yang Liu and Hsuan-Wei Lee

We investigate the dissipative dynamics of quantum population and coherence among different network topologies of a quantum network using a quantum spin model coupled to a thermal bosonic reservoir. Our study proceeds in two parts. First, we analyze a small network of Ising spins embedded in a large dissipative bath, modeled via the Lindblad master equation, where temperature arises naturally from system-bath coupling. This approach reveals how network topology shapes quantum dissipative dynamics, providing a basis for controlling quantum coherence through tailored network structures. Second, we propose a mean-field approach that extends the network to larger scales and captures dissipative dynamics in large-scale networks, connecting network topology to quantum coherence in complex systems and revealing the sensitivity of quantum coherence to network structure. Our results highlight how dissipative quantum dynamics depend on network topology, providing insight into the coherent dynamics of entangled states in networks. These results may be extended to dynamics in complex systems such as opinion propagation in social models, epidemiology, and various condensed-phase and biological systems.
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Materials Science

First-Principles Study of Mg-Induced Phase Stabilization in Ga$_2$O$_3$ polymorphs

Viswesh Prakash, Jingyu Tang, Lisa M. Porter et al. (+1 more)

In this study, we investigate the effect of Mg incorporation on the relative phase stability of the four primary Ga$_2$O$_3$ polymorphs using density functional theory (DFT) calculations, with the goal of rationalizing experimental observations suggesting that diffusion from MgAl$_2$O$_4$ substrates contributes to relative stabilization of the $\gamma$ phase. Mg incorporation is modeled up to 25% of Ga sites within supercells derived from fully relaxed unit cells of each polymorph. Our results show that while $\beta$-Ga$_2$O$_3$ remains the thermodynamically most stable phase, the enthalpic differences between polymorphs decrease with increasing Mg content. The inherently disordered $\gamma$ phase, with its high configurational entropy, becomes less energetically unfavorable under Mg substitution, suggesting that entropy-driven stabilization may facilitate its formation under high-temperature and/or nonequilibrium growth conditions such as those previously reported. These findings provide a thermodynamic rationale for the experimental observation of the $\gamma$ phase during epitaxial growth on MgAl$_2$O$_4$ spinel substrates.
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All authors Viswesh Prakash, Jingyu Tang, Lisa M. Porter, Rachel C. Kurchin

Materials Science · Cross-listed from physics.comp-ph

Bayesian identification of fibrous insulation thermal conductivity towards design of spacecraft thermal protection systems

Alex Alberts, Akshay Jacob Thomas, Kamran Daryabeigi et al. (+1 more)

The design of spacecraft thermal protection systems (TPS) requires accurate knowledge of thermal transport properties across wide ranges of temperature and pressure. For fibrous insulation, conventional measurement techniques in laboratory settings are typically limited to temperatures much lower than what is reached in atmosphere entry scenarios. Moreover, it is often the case that only temperature measurements are available, meaning that the thermal conductivity of the insulation must be indirectly inferred as an inverse problem. We propose a Bayesian framework using information field theory (IFT) to reconstruct the thermal conductivity of high-temperature fibrous insulation from sparse experimental data. Under IFT, the conductivity is represented as a Gaussian process, and the physics is enforced via a physics-informed prior over the temperature derived from the heat equation. Bayes's rule produces an infinite-dimensional posterior distribution that quantifies uncertainty about the conductivity which can be evaluated in extrapolation regimes. We apply the method to Opacified Fibrous Insulation with both synthetic and experimental data to reconstruct the thermal conductivity beyond the experimental regime. The inferred conductivities are validated against reference data and then propagated into high-fidelity digital twins of flexible TPS performance under Mars and Earth entry trajectories. The results show that IFT yields accurate predictions with quantified uncertainty, enabling robust TPS sizing in regimes inaccessible to direct measurement.
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All authors Alex Alberts, Akshay Jacob Thomas, Kamran Daryabeigi, Ilias Bilionis

Materials Science

Controlling HER activity and stability of $\gamma$- and 6,6,12-Graphyne through engineered B-N doping: DFT and Reactive MD simulations

Juan Gomez Quispe, Matheus Medina, Subhendu Mishra et al. (+3 more)

Graphynes offer a chemically heterogeneous $sp/sp^{2}$ carbon framework with distinct electronic regimes and site-selective reactivity. Here, Density Functional Theory and Reactive Molecular Dynamics Simulations are combined to evaluate pristine, B-doped, N-doped, and B-N co-doped $\gamma$-graphyne and 6,6,12-graphyne (meta/ortho/para). $\gamma$-graphyne is a semiconductor, while 6,6,12-graphyne exhibits an anisotropic Dirac-like semi-metallic dispersion. B/N substitution reconstructs near-$E_F$ states via dopant $\pi$ hybridization, and B-N pairing stabilizes defects through donor-acceptor compensation, with the ortho substitutions being the most favorable. Hydrogen adsorption remains weak on pristine lattices but becomes locally optimized upon doping, with near thermo-neutral $\Delta G_{\mathrm{ads}}$ 'hot spots' predominantly on $sp$-proximate carbon sites adjacent to the dopants. Reactive MD at 300 K further reveals an activity stability trade-off: B-N ortho in $\gamma$-graphyne sustains controlled hydrogen uptake without catastrophic bond scission, whereas B-N meta/para degrade, and 6,6,12-graphyne is generally more susceptible to over-hydrogenation. These results identify the B-N geometry as a key design variable for graphyne-based HER catalysts, which require both a favorable $\Delta G_{\mathrm{ads}}$ and finite-temperature hydrogenation stability.
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All authors Juan Gomez Quispe, Matheus Medina, Subhendu Mishra, Douglas S Galvao, Abhishek Singh, Pedro Alves da Silva Autreto

Mesoscale and Nanoscale Physics

Demonstration of a Field-Effect Three-Terminal Electronic Device with an Electron Mobility Exceeding 40 Million cm^2/(Vs)

T. J. Martz-Oberlander, B. Bulgaru, Z. Berkson-Korenberg et al. (+6 more)

We report the fabrication and operation of a source-drain-gate three-terminal field-effect electronic device with an electron mobility exceeding $40\times 10^6$ cm$^2$ / (Vs). Several devices were fabricated, with the highest achieved electron mobility obtained using a symmetrically-doped GaAs/AlGaAs quantum well forming a two-dimensional electron gas (2DEG) with a density of $1.47(1) \times 10^{11}$ cm$^{-2}$ and a pristine, pre-fabrication electron mobility of $44(2) \times 10^6$ cm$^2$/(\text{Vs}). To circumvent the well-known degradation of electron mobility during fabrication, devices were fabricated using a flip-chip technique where all lithographic processing steps were performed on a separate sapphire substrate. This method demonstrates the successful operation of various gate assembly designs on distinct 2DEGs without observable mobility degradation. This advance doubles the previous record for field-effect electronic device mobility and enables access to new regimes of quantum transport and applications that were previously unfathomable due to mobility limitations.
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All authors T. J. Martz-Oberlander, B. Bulgaru, Z. Berkson-Korenberg, Q. Hawkins, K.W. West, K.W. Baldwin, A. Gupta, L. N. Pfeiffer, G. Gervais