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Physics Condensed Matter Materials Science

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Friday 13 March

Materials Science · Cross-listed from physics.ins-det

Indirect monitoring of fast-charge cycling behavior of an energy-storage device-analysis of ambient temperature variations

Pertti O. Tikkanen

I present a reanalysis of temperature data from a publicly available certified laboratory report that documented the self-discharging behavior of an energy-storage device during 10 days. Graphs of temperature variations of both the tested device itself and the test chamber (fume hood) were given mainly for monitoring without further analysis, and variations in the ambient temperature signal were attributed to "other cells being cycled simultaneously in the same fume hood". I show that the ambient temperature signal alone – together with some quite mild and reasonable assumptions – allow to extract previously unpublished information on the simultaneously run test on the other cells: 1) the number of charge/discharge cycles 2) the cycle period, 3) the charge/discharge half-cycle asymmetry, and – most significantly – evidence that 4) the mentioned "other device" completed 338 full charge/discharge cycles at 3C rate at room temperature without any detectable thermal degradation signature.
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Materials Science

Production of Low-Density Aerogel Nuclear Fuels for Use in Fission Fragment Rockets and Novel Reactor Design

Noah D'Amico, Sandeep Puri, Ian Jones et al. (+4 more)

Graphene hydrogels were created and loaded with uranyl nitrate or thorium nitrate and freeze-dried to produce graphene aerogel nuclear fuels. These aerogels had densities between 0.018-0.035 g/cm3 and consisted of ~7.3 +- 0.5% uranium/thorium by mass. The ultra-low density of the aerogels allows for high energy ions to escape the fuel particles without depositing all their energy as heat, as is typical in nuclear fuels. Their measured alpha activity was ~16 pCi/mg, which could be enhanced up to ~49 pCi/mg by decreasing the thickness of aerogel samples to allow all alpha particles to escape. Additionally, high energy neutrons were used to induce fission to provide a source of fission fragments from the aerogel fuels. This novel form of nuclear fuel has potential applications in space propulsion such as fission fragment rocket engines, as well as in terrestrial applications for modular reactors, direct conversion methods, and in medical radiotherapeutics.
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All authors Noah D'Amico, Sandeep Puri, Ian Jones, Andrew Gillespie, Cuikun Lin, Bo Zhao, R. V. Duncan

Materials Science

Coupled Ferroelectricity and Phonon Chirality

Xiang-Bin Han, Cong Yang, Rui Sun et al. (+10 more)

The ability to control chirality and chiral phonons offers a route to manipulate the direction of spin and angular-momentum transport. In materials with rigid structural chirality, such as quartz, phonon chirality is fixed by the handedness and cannot be switched. By contrast, ferroelectric materials host a spontaneous polarization that can be reversibly switched by an external electric field. When chirality is coupled to this ferroelectric polarization, it enables electrical switching of crystal chirality and the associated phonon angular momentum, which is compatible with solid-state spintronic architectures, enabling control over chirality-dependent quantum states.1 Here, we report the experimental demonstration of the coupling between ferroelectricity and phonon chirality in the molecular ferroelectric triglycine sulfate. By electrically switching the crystal chirality, we achieve reversible and device-compatible control of phonon chirality, as revealed by in situ time-resolved magneto-optical Kerr effect measurements. The Kerr rotation reverses with electric-field switching, while phonon chirality vanishes in the paraelectric phase and is tunable in the racemic ferroelectric state. Furthermore, density functional theory calculations and circularly polarized Raman spectroscopy further corroborate the opposite circular phonon motions. These results establish an electrically addressable coupling pathway linking ferroelectricity, structural chirality, chiral phonons, and spin, opening a route toward chiral-phonon-enabled spin and phonon control technologies based on ferroelectric materials.
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All authors Xiang-Bin Han, Cong Yang, Rui Sun, Xiaotong Zhang, Thuc Mai, Zhengze Xu, Aryan Jouneghaninaseri, Xiaoning Jiang, Rahul Rao, Yi Xia, Dali Sun, Jun Liu, Xiaotong Li

Materials Science

Competing Magnetic Ground States in Copper-Doped Pb$_{10}$P$_{6}$O$_{25}$

Lin Hou, Kevin Allen, Christopher Lane et al. (+1 more)

We investigate the electronic and magnetic properties of copper-doped Pb$_{10}$(PO$_4$)$_6$O using a combination of density functional theory and many-body perturbation theory. The flat half-filled electronic band at the Fermi level is found to give way to an incommensurate antiferromagnetic instability with wave vector $(0.28\pi ,\pm 0.47\pi ,\pi )$ within the random phase approximation arising predominantly from Cu-$d_{yz}$ and Cu-$d_{xz}$ orbitals. Moreover, the Heisenberg exchange coupling between neighboring copper atoms is estimated to be $\sim 1$ meV. Our results suggest that magnetism in copper-doped Pb$_{10}$(PO$_4$)$_6$O is localized on the impurity copper site, with no long-range ordering. These findings support the picture that copper behaves as a magnetic impurity within the Pb-apatite matrix.
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All authors Lin Hou, Kevin Allen, Christopher Lane, Jian-Xin Zhu

Materials Science

Analyzing coherent phonon mode-conversion in gradient superlattices with atomistic wave-packet simulations

Evan Wallace Doe, Theodore Maranets and Yan Wang

In this study, we have used atomistic phonon wave-packet simulations to investigate the manifestation of coherent phonons and phonon transmission in gradient superlattices (SL) based on ordered arrangements of varied SL period sizes. We specifically explore how coherent mode-conversion in these quasi-periodic structures changes as function of three key structural parameters: (1) the number of distinct period sizes, (2) the number of periods present for each distinct period size, and (3) the arrangement of period sizes in either an ascending or descending arrangement. Comparisons to periodic SLs and aperiodic SLs are highlighted, revealing that coherent phonons in gradient SLs generally exhibit behaviors characteristic of intermediate states between the fully ordered and disordered structures. Interestingly, changes to the short-range order of GMLs does not significantly influence transmission, indicating that long-range disorder is far more important to coherent mode-conversion. Our results indicate that manipulating the long-range disorder of interfaces could be an effective strategy to tailor phonon thermal conductivity of SL architectures.
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Materials Science

Co2SeO3Cl2: Studies of Emerging Magnetoelectric Coupling in a Polar, Buckled Honeycomb Material

Faith O. Adeyemi, Xudong Huai, Mohamed Kandil et al. (+3 more)

The development of magnetoelectric materials requires chemical design strategies that integrate structural polarity with magnetic lattices capable of supporting competing spin interactions. Here, we demonstrate such an approach in the polar, buckled honeycomb magnet Co2SeO3Cl2. Magnetization and heat-capacity measurements reveal strong magnetic anisotropy and four successive magnetic transitions at 25.4, 16.8, 11, and 3 K. The recovered magnetic entropy through the ordering regime is only around half of the expected 2Rln(2), indicating persistent spin fluctuations. Second-harmonic generation measurements show three pronounced intensity anomalies at 11, 17, and 26 K that coincide with magnetic transitions while revealing that the crystallographic symmetry is preserved. Together, these results demonstrate that polar, buckled honeycomb magnets offer an unconventional phase space for coupling magnetic and electric dipoles in magnetoelectric materials.
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All authors Faith O. Adeyemi, Xudong Huai, Mohamed Kandil, Pradip Karki, Wencan Jin, Thao T. Tran

Materials Science

Smoothed Boundary Method Framework for Electrochemical Simulation of Li-ion Battery Cathode with Complex Microstructure: Model, Formulation and Parameterization

Hui-Chia Yu, Bernardo Orvananos, Scott Cronin et al. (+3 more)

Rechargeable battery electrodes have highly complex microstructures, consisting of nonuniform electrode particles, tortuous electrolyte channels, and irregular particle-electrolyte interfaces. Moreover, the electrochemical processes involve several coupled physical mechanisms, including mass transport in the electrode particles and electrolyte, current continuity in the solid and liquid, and electrochemical surface reactions. These geometric and mechanistic complexities create a challenging barrier of electrochemical simulations at the microstructural level using conventional methods. In this paper, we introduce a smoothed-boundary method (SBM) electrochemical simulation framework for modeling the electrochemical dynamics of complex battery electrode microstructures. The conventional governing equations are reformulated into SBM versions, and are solved using uniform Cartesian grids. The simulations utilize an image-based, experimentally reconstructed 3D microstructure as the input geometry, and the physical parameters acquired from experimental measurements. Two models of lithiation mechanisms, solid-solution and two-phase, are examined under potentiostatic discharging of a Li$_x$CoO$_2$ composite cathode. Detailed dynamics of the complex cathode microstructure are revealed through the simulations. The comparison between the two models indicates that modeling two-phase lithiation with Fick's diffusion will overestimate the electrode's performance. The presented simulation framework provides an innovative avenue in exploring the electrochemical dynamics at the microstructural level.
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All authors Hui-Chia Yu, Bernardo Orvananos, Scott Cronin, Martin Bazant, Scott Barnett, K. Thornton

Materials Science · Cross-listed from cond-mat.mes-hall

Overcoming intrinsic material limitations through cavity feedback

M. Ebrahimi, Y. Huang, V.A.S.V. Bittencourt et al. (+3 more)

Magnons, the quanta of spin waves, have significant potential for use in modern technologies, especially when strongly coupled to another mode for read-out and control. However, while magnons strongly interact with microwave photons via the magnetic-dipole interaction to form hybrid cavity-magnon polariton modes, the weak magnetostrictive magnon-phonon interaction, together with large polariton linewidths dominated by magnon dissipation, has so far restricted magnonic-spheres to the weak-coupling regime. The material-limited magnon dissipation rate in particular has been regarded as an unavoidable limitation in these systems. Here, we surpass this long-standing limitation by implementing an active microwave feedback loop to suppress the linewidth of cavity-magnon polaritons and strongly suppress their effective decay rate below the magnon-limited linewidth, thereby enhancing the polariton-phonon cooperativity from C=1 to C=150. As a key milestone, we achieve normal-mode splitting between a cavity-magnon polariton and a mechanical mode, providing direct evidence of three-mode hybridization among photons, magnons, and phonons. Our results establish feedback as a general route to accessing strong-coupling regimes in systems previously thought to be limited by material properties and hence open new opportunities for coherent control in hybrid quantum systems.
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All authors M. Ebrahimi, Y. Huang, V.A.S.V. Bittencourt, A. Rashedi, A. Metelmann, J.P. Davis

Materials Science

Efficient prediction of highly anisotropic excitonic properties in the layered antiferromagnet CrSBr via time-dependent density functional theory

Ashwin Ramasubramaniam, Daniel Hernangómez-Pérez, Javier Junquera et al. (+1 more)

CrSBr, a layered anisotropic van der Waals antiferromagnet, has recently emerged as a versatile platform where strong coupling between optical excitations and magnetic order enables magneto-optical control in low dimensions. While experiments have progressed rapidly, predictive and reliable ab initio descriptions remain limited to self-consistent, many-body perturbation theory that is computationally expensive and technically challenging. Here we present an alternative approach that accurately predicts the electronic and optical properties of CrSBr at substantially lower computational cost, while retaining quantitative accuracy in the coupling between excitons and magnetic order. Using a tuned hybrid density functional with on-site corrections, we reproduce fundamental and optical gaps and quantitatively capture the interaction between excitonic transitions and magnetic order. We then employ this functional to investigate excitonic shifts induced by spin canting, that would result from applying an external magnetic field. Our results establish an efficient framework for modeling excitonic and magneto-optical phenomena in layered magnetic semiconductors.
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All authors Ashwin Ramasubramaniam, Daniel Hernangómez-Pérez, Javier Junquera, María Camarasa-Gómez

Materials Science

Diffusion-based Generative Machine Learning Model for Predicting Crack Propagation in Aluminum Nitride at the Atomic Scale

Jiali Lu and Shengfeng Yang

Predicting atomic-scale crack propagation in aluminum nitride (AlN) is critical for semiconductor reliability but remains prohibitively expensive via molecular dynamics (MD). We develop a diffusion-based generative machine learning model to predict atomic-scale crack propagation in AlN, a critical semiconductor material, by conditioning solely on initial microstructure embeddings. Trained on MD simulations of single-crack systems, the model achieves a significant speedup while accurately forecasting dynamic fracture processes, including stress-driven crack initiation, crack branching, and atomic-scale bridging ligaments. Crucially, it demonstrates inherent physical fidelity by reproducing material-intrinsic mechanisms while disregarding periodic boundary artifacts, and generalizes to unseen multi-crack configurations. Validation against MD ground truth confirms the capability of the model to capture complex fracture physics without auxiliary stress or energy data, enabling rapid exploration of crack-mediated failure for semiconductor reliability optimization.
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Materials Science · Cross-listed from stat.ML

Filtered Spectral Projection for Quantum Principal Component Analysis

Sk Mujaffar Hossain and Satadeep Bhattacharjee

Quantum principal component analysis (qPCA) is commonly formulated as the extraction of eigenvalues and eigenvectors of a covariance-encoded density operator. Yet in many qPCA settings the practical goal is simpler: projection onto the dominant spectral subspace. Here we introduce a projection-first framework, the Filtered Spectral Projection Algorithm (FSPA), which bypasses explicit eigenvalue estimation while preserving the relevant spectral structure. FSPA amplifies any nonzero warm-start overlap with the leading subspace and remains robust in small-gap and near-degenerate regimes, without artificial symmetry breaking in the absence of bias. We show that FSPA achieves an oracle complexity $\mathcal{O}((\log(1/\epsilon)+\log(1/|a_1|^2))/\log(\lambda_1/\lambda_2))$,which is tight by a matching lower bound, establishing it as anoptimal projection primitive. We derive a convergence rate for degenerate spectra, give a circuit resource analysis with $n+\mathcal{O}(1)$ qubit overhead independent of system dimension, and extend the method to threshold spectral projection, Threshold-FSPA, which converges in $\mathcal{O}(\log(1/\epsilon))$ calls when the threshold lies between eigenvalues. In the density matrix exponentiation access model, FSPA gives an exponential copy-complexity advantage over classical methods. For classical datasets, we show that for amplitude-encoded centered data the ensemble density matrix $\rho=\sum_i p_i|\psi_i\rangle\langle\psi_i|$ equals the covariance matrix. Numerical tests on chemistry density matrices, noisy circuit outputs, Breast Cancer Wisconsin, handwritten Digits, and 1–4-qubit scalability confirm the theory. A minimal Qiskit implementation validates magnitude invariance, signal amplification, and no spurious symmetry breaking. These results establish FSPA as an optimal and deployable quantum spectral projection primitive.
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Materials Science · Cross-listed from physics.ins-det

Development of a high-field pulsed magnet and optical fiber coupled cryostat system for magneto-photoluminescence measurements

Deepesh Kalauni, Kingshuk Mukhuti, Tao Peng et al. (+1 more)

This paper presents the development of a high field pulsed magnet system combined with an optical fiber-coupled low temperature cryostat for magneto-photoluminescence measurements. A novel aspect of our system is the use of electrolyte capacitors in a 75 kJ capacitor bank to drive the pulsed magnet, enabling the generation of high magnetic fields at a relatively low charging voltage (400 V). The zylon reinforced wire wound magnet coil achieves a maximum field strength of 35 tesla with a magnetic field rise time of 10 ms. The integrated cryostat was developed to meet the specific requirements of magneto-photoluminescence experiments using a 4 K helium closed-cycle cryocooler to provide a stable low-temperature environment down to 5 K.
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All authors Deepesh Kalauni, Kingshuk Mukhuti, Tao Peng, Bhavtosh Bansal

Materials Science

Electromechanical Hysteresis in Phase Change Material Sb2S3

Jack Kaman, Evan Musterman, Kyle P. Kelley et al. (+3 more)

Antimony sulfide is an emerging phase change material for optical and electrical memory and computation elements. It has additionally been reported as a ferroelectric, with recent evidence from hysteresis in piezoresponse force microscopy. Here, we complete a rigorous set of piezoresponse force microscopy experiments on a congruently crystallized Sb2S3 glass-ceramic, where piezoelectric coupling should be forbidden in glassy Sb2S3. We replicate previous results and reveal that the behavior is absent in glassy Sb2S3 but show that the response originates primarily from non-piezoelectric contributions to the signal caused by an applied voltage. This hysteretic behavior in piezoresponse force microscopy is quite similar to some electrochemically active non-ferroelectric oxides, but uniquely, it appears here with a very clear spatial contrast that is decoupled from surface topography. This shows that the electromechanical signal reflects bulk-like properties and reveals differences in electrical behavior of crystalline and amorphous phases of Sb2S3.
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All authors Jack Kaman, Evan Musterman, Kyle P. Kelley, Neus Domingo-Marimon, Volkmar Dierolf, Himanshu Jain

Materials Science · Cross-listed from cond-mat.mes-hall

First-principles predictions of band alignment in strained Si/Si1-xGex and Ge/Si1-xGex heterostructures

Nathaniel M. Vegh, Pericles Philippopoulos, Raphaël J. Prentki et al. (+4 more)

Accurate band offsets are essential for predictive continuum modeling of nanostructures such as quantum wells and quantum dots formed in strained Si/Si1-xGex and Ge/Si1-xGex heterostructures. Experimental offset data for these systems remain sparse away from endpoint compositions, making composition-dependent design difficult. We use atomistic first-principles density functional theory to compute valence- and conduction-band offsets across the full range 0 <= x <= 1. Random alloying is treated with special quasirandom structures, interface lineup terms are extracted from macroscopically averaged local Kohn-Sham potentials in thick periodic superlattices, valence-band spin-orbit coupling is included through species-resolved Mulliken weights, and conduction-band edges are refined using the screened hybrid Heyd-Scuseria-Ernzerhof functional. The resulting offsets show pronounced composition nonlinearity beyond the linear models explored in previous works, agree with experimental benchmarks, and reproduce the high-Ge slope change in the relaxed-alloy band gap. Analytic fitting expressions are provided for direct use in simulations, facilitating practical design of modern quantum technology devices.
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All authors Nathaniel M. Vegh, Pericles Philippopoulos, Raphaël J. Prentki, Wanting Zhang, Yu Zhu, Félix Beaudoin, Hong Guo

Materials Science

A Spatial Localizer for Electrons in Insulators

Haylen Gerhard, Yifan Wang, Alexander Cerjan et al. (+1 more)

The location of electrons governs phenomena ranging from chemical bonding and electric polarization to the topological classification of band insulators and the emergence of correlated states in quantum matter. While a prescription exists for finding local state representations of electrons in one-dimensional insulators, no comparably general theory exists in higher dimensions. Here, we introduce a general framework for finding the location of electrons in insulators in two and three dimensions based on the spectral properties of quantum-mechanical operators that we term Spatial Localizers. This framework naturally extends the notion of Wannier centers to insulators with boundaries, defects, and disorder, which we use to establish a position-space formulation of the bulk-defect correspondence for electronic charge. This framework also yields maximally localized electronic states. As two representative examples, we show that these states reduce to maximally localized Wannier functions in atomic insulators, whereas in Chern insulators they form coherent states that mirror the coherent-state structure of Landau levels in the quantum Hall effect.
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All authors Haylen Gerhard, Yifan Wang, Alexander Cerjan, Wladimir A. Benalcazar

Materials Science

Microscopic flexoelectricity in the canonical PMN relaxor

J. Hlinka

Previously reported neutron scattering investigations of the canonical relaxor ferroelectric perovskite oxide with a chemical formula Pb(Mg(1/3)Nb(2/3))O3 (PMN) are revisited in order to appreciate the role of the intrinsic bulk flexoelectricity. Despite the outstanding electromechanical properties of lead-based relaxors, the magnitude of the flexoelectric coupling coefficient derived here directly from the PMN neutron diffuse scattering data, does not exceed the range of values typical for conventional perovskite ferroelectrics. We explain how these findings are related in the framework of the Ginzburg-Landau-Devonshire and the ferroelectric soft mode theory. We propose that the relaxor properties of PMN might be related to the suppression of the transverse correlation length of the flexoelectrically hybridized translational-polarization fluctuations due to its closeness to the Lifshitz-point regime.
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Materials Science · Cross-listed from physics.comp-ph

From Experiments to Expertise: Scientific Knowledge Consolidation for AI-Driven Computational Physics

Haonan Huang

While large language models (LLMs) have transformed AI agents into proficient executors of computational materials science, performing a hundred simulations does not make a researcher. What distinguishes research from routine execution is the progressive accumulation of knowledge - learning which approaches fail, recognizing patterns across systems, and applying understanding to new problems. However, the prevailing paradigm in AI-driven computational science treats each execution in isolation, largely discarding hard-won insights between runs. Here we present QMatSuite, an open-source platform closing this gap. Agents record findings with full provenance, retrieve knowledge before new calculations, and in dedicated reflection sessions correct erroneous findings and synthesize observations into cross-compound patterns. In benchmarks on a six-step quantum-mechanical simulation workflow, accumulated knowledge reduces reasoning overhead by 67% and improves accuracy from 47% to 3% deviation from literature - and when transferred to an unfamiliar material, achieves 1% deviation with zero pipeline failures.
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Materials Science · Cross-listed from cs.CE

Lattice Discrete Particle Model (LDPM): Comparison of Various Time Integration Solvers and Implementations

Erol Lale, Jan Eliáš, Ke Yu et al. (+17 more)

This article presents a comparison of various implementations of the Lattice Discrete Particle Model (LDPM) for the numerical simulation of concrete and other heterogeneous quasibrittle materials. The comparison involves the use of transient implicit and explicit solvers and steady-state (static) solvers and implementations for Central Processing Unit (CPU) as well as Graphics Processing Unit (GPU). The various implementations are compared on the basis of a set of benchmarks tests describing behaviors of increasing computational complexity. They include elastic vibrations, confined strain-hardening compressive response, tensile fracture, and unconfined strain-softening compressive response. Metrics of interest extracted from the simulations include macroscopic stress versus strain responses, computational times, number of iterations, and energy balance error. Pairwise comparison of final crack patterns is provided through the correlation coefficient and normalized root mean square error of the crack opening vectors. Moreover, for the most numerically challenging case of unconfined compression with sliding boundary conditions, the stability of the strain-softening response is tested by perturbing the solutions as well as changing the convergence criteria and time step size. Attached to this paper is the complete input data of the benchmark tests; this will allow researchers to run the examples and compare them with their own implementations. In addition, most of the reported implementations are publicly available in open source packages.
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All authors Erol Lale, Jan Eliáš, Ke Yu, Matthew Troemner, Monika Středulová, Julien Khoury, Tianju Xue, Ioannis Koutromanos, Alessandro Fascetti, Bahar Ayhan, Baixi Chen, Giovanni Di Luzio, Yuhui Lyu, Madura Pathirage, Gilles Pijaudier-Cabot, Lei Shen, Alessandro Tasora, Lifu Yang, Jiawei Zhong, Gianluca Cusatis

Materials Science · Cross-listed from quant-ph

Quantifying surface losses in superconducting aluminum microwave resonators

Elizabeth Hedrick, Faranak Bahrami, Alexander C. Pakpour-Tabrizi et al. (+11 more)

The recent realization of millisecond-scale coherence with tantalum-on-silicon transmon qubits showed that depositing the Al/AlOx/Al Josephson junction in a high purity, ultrahigh vacuum environment was critical for achieving lifetime-limited coherence, motivating careful examination of the aluminum surface two-level system (TLS) bath. Here, we measure the microwave absorption arising from surface TLSs in superconducting aluminum resonators, following methodology developed for tantalum resonators. We vary film and surface properties and correlate microwave measurements with materials characterization. We find that the lifetimes of superconducting aluminum resonators are primarily limited by surface losses associated with TLSs in the 2.7 nm-thick native AlOx. Treatment with 49% HF removes surface AlOx completely; however, rapid oxide regrowth limits improvements in surface loss and long term device stability. Using these measurements we estimate that TLSs in aluminum interfaces contribute around 27% of the relaxation rate of state-of-the-art tantalum-on-silicon qubits that incorporate aluminum-based Josephson junctions.
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All authors Elizabeth Hedrick, Faranak Bahrami, Alexander C. Pakpour-Tabrizi, Atharv Joshi, Q. Rumman Rahman, Ambrose Yang, Ray D. Chang, Matthew P. Bland, Apoorv Jindal, Guangming Cheng, Nan Yao, Robert J. Cava, Andrew A. Houck, Nathalie P. de Leon

Materials Science · Cross-listed from quant-ph

Beta Tantalum Transmon Qubits with Quality Factors Approaching 10 Million

Atharv Joshi, Apoorv Jindal, Paal H. Prestegaard et al. (+9 more)

Tantalum-based transmon qubits are a promising platform for building large-scale quantum processors. So far, these qubits have been made from tantalum films grown exclusively in the alpha phase ({\alpha}-Ta). The beta phase of tantalum (\{beta}-Ta) readily nucleates at room temperature, making it attractive for scalable qubit fabrication. However, \{beta}-Ta is widely believed to be detrimental to qubit performance because it has a lower superconducting critical temperature than {\alpha}-Ta. We challenge this prevailing belief by fabricating low-loss transmon qubits from \{beta}-Ta films on sapphire. Across 11 qubits, the mean time-averaged quality factor is (5.6 +/- 2.3) x 10^6, with the best qubit recording a time-averaged quality factor of (10.1 +/- 1.3) x 10^6. Resonator studies demonstrate that the dominant microwave loss channel is surface two-level systems, with the surface loss contribution for \{beta}-Ta being about twice that of {\alpha}-Ta. \{beta}-Ta films exhibit significant kinetic inductance, consistent with an estimated magnetic penetration depth of (1.78 +/- 0.02) {\mu}m. This work establishes \{beta}-Ta on sapphire as a material platform for realizing low-loss transmon qubits and other superconducting devices such as compact resonators, kinetic inductance detectors, and quasiparticle traps.
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All authors Atharv Joshi, Apoorv Jindal, Paal H. Prestegaard, Faranak Bahrami, Elizabeth Hedrick, Matthew P. Bland, Tunmay Gerg, Guangming Cheng, Nan Yao, Robert J. Cava, Andrew A. Houck, Nathalie P. de Leon

Materials Science

Zinc selenide single crystals co-doped with active TM-ions of chromium, cobalt and iron

Sergei Naydenov, Oleksii Kapustnyk, Igor Pritula et al. (+1 more)

The development of laser materials with absorption/emission spectra in the atmospheric transparency band 2-5 microns is of great interest for modern applications. Triple-doped zinc selenide crystals activated with chromium, cobalt, and iron ions were grown by the vertical Bridgman method under high argon pressure. Comparative X-ray diffractometry, infra-red spectroscopy, and other studies of grown crystals were conducted. Features of their growth, morphology, and optical properties related to the crystal structure were discovered.
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All authors Sergei Naydenov, Oleksii Kapustnyk, Igor Pritula, Dmitro Sofronov

Materials Science · Cross-listed from cond-mat.mes-hall

Nested Feature Spectrum Topology: Tripartite Topological Equivalence of Feature, Entanglement, and Wilson Loop Spectrum

Yi-Chun Hung, T. Tzen Ong and Hsin Lin

Topological phases of matter are traditionally characterized through symmetry-based classifications. In cases of symmetry breaking, the projected spectrum - obtained by projecting the ground state onto the eigenstates of a pertinent quantum observable, such as spin or orbital angular momentum - provides a clear method for classifying topological phases. This approach underpins well-known frameworks such as spin-resolved topology and feature spectrum topology. Here we introduce nested feature spectrum topology, in which projection operators are applied recursively to subsectors of the feature spectrum, generating a hierarchy of feature spectra. We uncover a fundamental tripartite equivalence among the topology of feature, the entanglement, and the Wilson loop spectra in non-interacting fermionic systems. This equivalence reveals that the feature spectrum encodes the entanglement between sectors of the quantum observable, such as the spin-up and spin-down states in spin-resolved topology. We further prove that spectral flow in the entanglement spectrum and the Wilson loop winding in the feature spectrum are equivalent manifestations of the feature-energy complementarity: the appearance of gapless spectral flow in either energy or projected spectra on the boundary. This complementarity refines the conventional bulk-boundary correspondence by demonstrating that topological boundary modes may persist in the feature spectrum even when energy spectra are gapped. Our results provide a deeper understanding and solid foundation for the origin of band topology in the feature spectrum.
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Materials Science

Rate-Dependent Reversibility and Lithium Losses in Hybrid Anode-Collector Metal Electrodes

Arturo Galindo, Jesus Diaz-Sanchez, Sunil Kumar et al. (+5 more)

Understanding how practical lithium storage capacity varies with charge-discharge rate is crucial for designing durable anode free lithium batteries. We examine the lithiation behavior of single element metal electrodes-Al (alloying), Mg (solid solution intercalation), Ag (solid solution then alloying), and Cu (surface Li plating)-to determine how their mechanisms influence reversibility, measured by coulombic efficiency. Using electrochemistry combined with depth resolved ion beam profiling, we map local coulombic efficiency across current densities and identify dominant lithium loss pathways. Ag uniquely sustains fast kinetics and high reversibility at elevated rates due to rapid formation of gamma brass-type alloy phases. In contrast, Mg and Al show increasing irreversibility from kinetically or structurally driven Li trapping, while Cu exhibits the largest losses through porous, highly reactive plated lithium. These results reveal fundamental limits of anode free systems that depend on reversible Li plating without excess lithium and underscore the importance of metal selection for stable, high rate performance.
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All authors Arturo Galindo, Jesus Diaz-Sanchez, Sunil Kumar, Bouthayna Alrifai, Andrea Marchetti, Gaston Garcia, Celia Polop, Enrique Vasco

Materials Science · Cross-listed from cond-mat.str-el

Putative quantum critical point in locally noncentrosymmetric CeCoGe$_2$ crystals

F. Garmroudi, C. S. T. Kengle, M. H. Schenck et al. (+4 more)

Locally noncentrosymmetric heavy-fermion compounds may produce long-sought correlated quantum phases, such as spin-triplet superconductivity with non-Abelian quasiparticles, but identifying the right candidate systems is challenging. Here, using the In flux method, we synthesize CeCoGe$_2$ single crystals, belonging to the highly tunable pseudotetragonal ($Cmcm$) Ce$TX_2$ family, which allows for substitutions at both the transition metal $T$ and at the $X$ sites. We identify a heavy-fermion ground state with a Sommerfeld coefficient $\gamma\approx 120$ mJ mol$^{-1}$ K$^{-2}$ and a non-Fermi-liquid exponent of the electrical resistivity, which may indicate its proximity to the putative quantum critical point. However, no signs of superconductivity or magnetic order are detected down to 20 mK. Our analysis of electrical transport and structural properties indicates that coherent charge transport and the emergence of superconductivity observed under hydrostatic pressure in related compounds (CePtSi$_2$ and CeRhGe$_2$) are suppressed in CeCoGe$_2$ by strong random potential scattering due to intrinsic Co vacancies (approximately 4% even in the highest-quality crystals). By tuning the growth stoichiometry and temperature profile, we demonstrate that the defect concentration can be controlled and has a pronounced effect on the residual resistivity. We hypothesize that superconductivity may be found in higher-quality CeCoGe$_2$ crystals grown by different techniques.
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All authors F. Garmroudi, C. S. T. Kengle, M. H. Schenck, J. D. Thompson, E. D. Bauer, S. M. Thomas, P. F. S. Rosa

Materials Science · Cross-listed from nlin.PS

Transition Waves for Energy Trapping and Harvesting

Sneha Srikanth and Andres F. Arrieta

The presence of multiple stable states and associated nonlinear phenomena, such as hysteresis, in multistable mechanical metamaterials enables frequency-independent energy harvesting and shock absorption. This study focuses on shock absorption achieved by locking transition waves to trap energy at designed locations within a multistable metamaterial. We further demonstrate that the same system can simultaneously harvest energy from impact loading, thereby exhibiting multifunctionality. The model of the multistable metamaterial is a one-dimensional chain of bistable units whose transition wave dynamics are related to topological solitary waves governed by the $\phi^4$ equation. This connection enables analytical estimation of critical design parameters required for energy trapping and also the amount of energy trapped. Numerical simulations and experiments show that trapping energy in transition waves leads to enhanced damping performance compared to corresponding linear metamaterials. We further propose design variations to increase the amount of energy trapped in the transition wave. Additionally, we identify energy splitting as a damping mechanism that arises when there are repeated impulses or a single high-amplitude impulse that generates multiple transition waves. The transition waves interact to produce localized, fast-dissipating breathers, leading to a damped response. Furthermore, experiments demonstrate that multistable metamaterials can simultaneously achieve improved energy harvesting and better damping performance compared to their linear counterparts. Together, these results highlight the use of transition waves for creating multifunctional multistable metamaterials.
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Materials Science · Cross-listed from cond-mat.mes-hall

Extending Topological Bound on Quantum Weight Beyond Symmetry-Protected Topological Phases

Yi-Chun Hung, Yugo Onishi, Hsin Lin et al. (+2 more)

The quantum metric encodes the geometric structure of Bloch wave functions and governs a wide range of physical responses. Its Brillouin-zone integral, the quantum weight, appears in the structure factor and provides lower bounds on observables such as the optical gap and dielectric constant. In symmetry-protected topological (SPT) phases, the nontrivial band topology imposes a lower bound on the quantum weight and constraints on the observables. Here, we generalize the topological bound on quantum geometry to encompass systems beyond the SPT phases. We show that topological invariants defined via the projected spectrum lower-bound the quantum weight with a symmetry-breaking correction to the quantum metric. Our proposed bound holds even when the underlying symmetries are broken, and it would be amenable to experimental verification via the optical conductivity sum rule under external fields. We illustrate our theory by adding a nonzero spin-orbit coupling term to a spin Chern insulator model, where we show that our proposed bound applies even though the conventional topological bound does not hold.
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All authors Yi-Chun Hung, Yugo Onishi, Hsin Lin, Liang Fu, Arun Bansil

Materials Science · Cross-listed from cond-mat.mes-hall

Imaging the high-frequency charging dynamics of a single impurity in a semiconductor on the atomic scale

Maialen Ortego Larrazabal, Jiasen Niu, Stephen R. McMillan et al. (+4 more)

As electronic devices approach the atomic limit, the charge dynamics of individual dopant atoms increasingly constrain performance, stability, and coherence. In scanning tunnelling microscopy (STM), donor ionization is typically interpreted as a static threshold process arising from tip-induced band bending. Here we show that the ionization of individual sulfur donors in InAs is intrinsically dynamic and governed by the local electric field. Using MHz-frequency STM noise spectroscopy with atomic-scale spatial mapping, we resolve pronounced random telegraph noise that is invisible in time-averaged tunnelling spectra. A bias-dependent model quantitatively links the noise spectra to microscopic ionization and neutralization processes of the donor states, enabling direct extraction of nanosecond charge-state lifetimes. The switching rate is strongly bias dependent, demonstrating that the electric field continuously drives charge-state transitions. Unexpectedly, we show that the degenerately doped bulk leads to a sharp bias-dependent onset of donor ionization as the donor level crosses the Fermi level, giving rise to a characteristic shoulder in the noise power spectrum that is captured by our model. These results establish donor ionization as a non-equilibrium dynamical process with nontrivial contribution by the bulk electrons, and identify impurity switching as a universal nanoscale charge-noise mechanism relevant to quantum devices.
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All authors Maialen Ortego Larrazabal, Jiasen Niu, Stephen R. McMillan, Paul M. Koenraad, Michael E. Flatté, Milan P. Allan, Ingmar Swart

Materials Science · Cross-listed from cond-mat.soft

Large dilatational hyperelasticity of glasses en route to cavitation failure

Pawandeep Kaur, Noam Ottolenghi, Edan Lerner et al. (+2 more)

Materials deform elasto-plastically and fail under various loading conditions, typically quantified by the stress triaxiality, which is the ratio between the dilatational (hydrostatic) stress and the deviatoric (shear-like) one. We show that the elasto-plastic deformation of glasses approaching failure qualitatively differ for large and small stress triaxiality levels. Specifically, in the former limit, glasses reveal a strong hyperelastic (nonlinear elastic) response with minute plasticity, largely independently of the quenching rate across the glass transition. Yet, glassy disorder gives rise to significant elastic (reversible) nonaffine deformation, accompanied by the formation of micro-cavities. A small fraction of the latter is irreversible, i.e., survives unloading prior to the onset of failure, and may serve as nucleation sites for failure in the form of large-scale cavitation, involving a topological transition accompanied by the formation of an internal free surface, upon which the glass loses a significant fraction of its load-bearing capacity. These results are contrasted with glass behavior in the limit of vanishing stress triaxiality and their universality across different glass formers is demonstrated. Finally, the implications of our findings for understanding glass deformation and failure under realistic stress conditions are discussed.
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All authors Pawandeep Kaur, Noam Ottolenghi, Edan Lerner, David Richard, Eran Bouchbinder

Materials Science · Cross-listed from cond-mat.str-el

Orbital dimerization-induced first-order structural phase transition: a case study in La$_3$Ni$_2$O$_7$

Xingchen Shen and Wei Ku

First-order structural phase transition is a common phenomenon in materials that qualitatively alters their physical properties. Yet, the abrupt first-order nature is usually unexplained by realistic computations, implying an omission of important physics in describing the electronic structure of the nearby stable phases. Using the recently discovered nickelate superconductors La$_3$Ni$_2$O$_7$ as a prototypical example, we demonstrate that such first-order nature is typically beyond intra-atomic correlation considered in state-of-the-art material computations. Instead, a full many-body treatment of low-energy active orbitals reveals a generic inter-atomic "orbital dimerization" mechanism of first-order structural phase transition, corresponding to abrupt energy reduction upon a spin-singlet bond formation. Such an inter-atomic correlation qualitatively changes not only the essential lattice bonding but also the characteristics of low-energy electronic properties across the transition. This strong mechanism and the developed computational framework are generally applicable to a wide variety of ionic materials, to produce valuable insights into atomic and electronic structures essential for their physical properties and functionalities.
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Materials Science · Cross-listed from cond-mat.str-el

Heat Capacity-A Powerful Tool for Studying Exotic States of Matter

K. Ramesh Kumar, Xudong Huai, Michał J. Winiarski et al. (+2 more)

Heat capacity measurements are a powerful tool that researchers rely on when studying the relationship between microscopic degrees of freedom and macroscopic behavior in condensed matter. This uniqueness stems from heat capacity capturing contributions from lattice, electronic, and magnetic components, as well as energy-level populations, enabling an effective approach to studying phase transitions and excitations across different classes of materials. However, analyzing heat capacity data presents a common, appreciable challenge for new researchers. Although comprehensive theoretical aspects of heat capacity are presented in several elegant textbooks, practical application remains a daunting task. To overcome this challenge, this tutorial guides researchers in collecting, analyzing, and interpreting heat capacity data in contemporary quantum materials. We outline the connections between thermodynamics, heat capacity, and entropy, as well as measurement methodology and data analysis for representative examples, including phonon dynamics, spin waves, superconductors, magnetic skyrmions, proximate quantum spin liquids, and heavy-fermion materials. Our goal is to provide a concise, accessible guide that enables new researchers to utilize heat capacity as a quantitative lens for understanding exotic states of matter.
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All authors K. Ramesh Kumar, Xudong Huai, Michał J. Winiarski, Allen O. Scheie, Thao T. Tran