Materials Science · Cross-listed from physics.ins-det
Model-derived conversion formula for real-time gas monitoring based on chemiresistive sensors
Fernando Massa Fernandes and Benoît Hackens
Chemiresistive gas sensors transduce gas adsorption into changes in the electrical resistance across a pair of electrodes connected by a sensitive layer of material. This type of sensor is used due to its simple operation, high sensitivity, low cost, and convenience for scaled-up manufacturing of microsized devices. The conversion of the electrical resistance to a corresponding gas concentration is often performed through calibration procedures using empirical formulas, overlooking part of the physical phenomena involved in the process, both on the sorption kinetics and on the transduction. Consequently, a direct evaluation of gas concentration is plagued by the response delays and slow recovery intrinsic to these processes. In contrast to this approach, here we first propose a physical model, based on gas-modulated potential barriers, and considering the out-of-
equilibrium dynamic response. Based on this model, we derive an original conversion formula able to dynamically convert the resistance changes into a corresponding gas concentration thus eliminating the main drawback related to slow response and recovery. This new strategy is demonstrated for real-time NO2 gas sensing, using chemiresistors based on oxidized PbS nanocrystals. In addition, the broader application of the proposed model and strategy is demonstrated for NH3 sensing, based on polypyrrole/gold junctions.
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Materials Science
Collapse of Jahn-Teller Phonons in La$_{1-x}$Sr$_{x}$MnO$_3$ with Weak Magnetoresistance
Tyler C. Sterling, Andrei T. Savici, Ryoichi Kajimoto et al. (+4 more)
Perovskite manganites are
quantum materials exhibiting competing interactions inducing colossal magnetoresistance (CMR). The prevailing theory of CMR highlights the essential role of electron-
phonon coupling (EPC), but mounting evidence suggests the underlying mechanism is more complicated. Here, we investigate
phonons and
spin-
phonon coupling in
ferromagnetic CMR manganites La$_{1-x}$Sr$_x$MnO$_3$ ($x$=0.2,0.3) with relatively small CMR associated with melting of the
magnetic order above room temperature. High-resolution
neutron scattering experiments combined with density functional theory (DFT) show that the low-temperature
ferromagnetic phase is conventional:
neutron scattering from
phonons agrees with DFT predictions and
magnons follow sinusoidal dispersions. Fluctuating
magnetic moments and low-energy
phonons remain conventional in the high temperature paramagnetic phase, indicating the Mn and La/Sr sublattices are not strongly perturbed by melting of ferromagnetism. In contrast, the Jahn-Teller-active optical oxygen vibrations collapse entirely above the Curie temperature, despite low CMR in these compositions, with some of the lost spectral weight reappearing as quasielastic scattering. We attribute this highly anomalous behavior to
giant EPC in the charge and/or orbital channel. It drives cooperative diffusive motion of quasistatic carrier-trapping oxygen sublattice distortions once ferromagnetism disappears. We hypothesize the magnitude of magnetoresistance correlates with the rate of
diffusion rather than with the strength of Jahn-Teller EPC.
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All authors Tyler C. Sterling, Andrei T. Savici, Ryoichi Kajimoto, Kazuhiko Ikeuchi, Nazir Khan, Frank Weber, Dmitry Reznik
Soft Condensed Matter
Inference of the 3D pressure field exerted by a single cell from a thin membrane transverse deformation
Quentin Bédel, Loïc Dupré and Nicolas Destainville
Numerous
cell types relate to their immediate environment by exerting a three-dimensional pressure field on their environment, with components both longitudinal and transverse to the
cell membrane. This pressure field can in principle be measured by traction force microscopy experiments. Compared to other approaches, the technique of Protrusion Force Microscopy gives access with high spatial resolution to the pressure field by measuring the deformation of a thin elastic membrane using atomic force microscopy (AFM). However, while the pressure field under interest is three-dimensional, the height profile measured by AFM is only one-dimensional. We propose a solution to this inverse problem and we explore its regime of applicability in the experimental context.
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Materials Science
Predicting Atomistic Transitions with Transformers
Henry Tischler, Wenting Li, Qi Tang et al. (+2 more)
Accurate knowledge of the atomistic transition pathways in materials and material surfaces is crucial for many material science problems. However, conventional simulation techniques used to find these transitions are extremely computationally intensive. Even with large-scale, accelerated material simulations, the computational cost constrains the applicable domain in practice. Machine learning models, with the potential to learn the complex emergent behaviors governing atomistic transitions as a fast surrogate model, have great promise to predict transitions with a vastly reduced computational cost. Here, we demonstrate how
transformers can be trained to predict atomistic transitions in nano-clusters. We show how we evaluate physical validity of the predictions and how a multitude of additional, different microstates can be generated by slightly varying the data provided to the model.
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All authors Henry Tischler, Wenting Li, Qi Tang, Danny Perez, Thomas Vogel
Strongly Correlated Electrons
Moiré-induced symmetry breaking of charge order in van der Waals heterostructures
Sandra Sajan, Laura Pätzold, Tarushi Agarwal et al. (+10 more)
Layered materials that stack different
lattice symmetries are rare in nature. Misfit layered chalcogenides, which combine square and hexagonal
lattices of rocksalt monochalcogenides and transition-metal dichalcogenides, provide a platform to explore how incommensurability and explicit
symmetry breaking impact collective electronic phases. Here we use low-temperature scanning tunneling microscopy/spectroscopy to probe the misfit compounds (MS)$_{1+\delta}$TaS$_{2}$ with M = Pb, Sn and track how the misfit interface reshapes the electronic ground state of the embedded 1H-TaS$_{2}$ monolayers. High-resolution STM imaging and
Fourier analysis reveal that the charge-density wave (CDW) is incommensurate and fragments into nanometer-sized domains. Strikingly, the CDW exhibits a pronounced and anisotropic response to the uniaxial moiré potential imposed by the misfit layer: its coherence lengths and ordering wavevectors become inequivalent, demonstrating a strong nonlinear coupling between the intrinsic CDW instability and the
symmetry-breaking moiré field. First-principles-informed multiscale modeling shows that this reorganization arises from the combined effect of interlayer charge transfer and the spatially anisotropic energy landscape introduced by the misfit interface. In contrast, superconductivity is comparatively insensitive to the moiré, revealing a uniform, single full-gap consistent with s-wave pairing. Our results establish heterosymmetry stacking as a route to engineer correlated states in van der Waals materials.
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All authors Sandra Sajan, Laura Pätzold, Tarushi Agarwal, Clara Pfister, Haojie Guo, Sisheng Duan, P. V. Sruthibhai, Mariana Rossi, Maria N. Gastiasoro, Sara Barja, Ravi P. Singh, Tim Wehling, Miguel M. Ugeda
Strongly Correlated Electrons
Exchange anisotropy-driven noncollinear magnetism and magnetic transitions in MnTiO3 ilmenite
Srimal Rathnayaka, Luke Daemen and Despina Louca
Evidence for multiple
magnetic transitions and unconventional
spin exchange interactions in the ilmenite
insulator MnTiO3 is provided via
neutron scattering. On cooling, while G-type
antiferromagnetic (AFM) order sets in first at 63 K with a k1 = (000) characteristic wave vector, a weaker second
magnetic transition with k2 = (00 3/2 ) appears near 42 K, giving rise to a noncollinear structure. Intrinsic buckling of the honeycomb
lattice along c creates bond anisotropy and a distorted
crystal field that can lead to exchange paths that modulate orbital overlap and
spin-orbit coupling. The inelastic spectrum is best described by
magnetic exchange anisotropy that breaks the local
symmetry of the honeycomb, with competing AFM Heisenberg, Dzyaloshinskii-Moriya and alternate intra-planar
ferromagnetic (FM) interactions, that may yield a weakly-coupled ladder system.
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Strongly Correlated Electrons
Magnetoelastic signatures of the conical state and charge density waves in antiferromagnetic FeGe
L. Prodan, J. Sourd, S. Zherlitsyn et al. (+1 more)
Kagome systems host intertwined
spin, charge, and
lattice degrees of freedom that drive emergent collective states. Here, we identify two distinct energy scales in the noncollinear kagome magnet FeGe: a field-tunable
magnetic fluctuation channel at $\sim 35$~K associated with the conical state, and a field-independent channel at $\sim 100$~K linked to charge-density-wave fluctuations. Ultrasound measurements provide direct access to the exchange-renormalized
magnetic stiffness, whose softening governs the acoustic anomaly and follows a
symmetry-constrained quadratic field dependence. We further predict a linear temperature dependence of
neutron diffraction intensities at fixed field and a quadratic field suppression at fixed temperature. These results identify
magnetic stiffness as a key control parameter of
spin-
lattice dynamics and establish ultrasound as a sensitive probe of coupled collective modes.
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All authors L. Prodan, J. Sourd, S. Zherlitsyn, L. Chioncel
Statistical Mechanics · Cross-listed from gr-qc
State-Selective Signatures of Quantum and Classical Gravitational Environments
Partha Nandi, Sankarshan Sahu, Bibhas Ranjan Majhi et al. (+1 more)
A unified framework is developed for determining whether a gravitational-wave (GW) background behaves as a classical field or as a genuinely
quantum environment. Unified here means that both descriptions originate from the same
tidal coupling derived from geodesic deviation, which yields an identical quadratic interaction
Hamiltonian for the detector; the only distinction lies in whether the GW degrees of freedom are modeled as classical phase-randomized coherent states or as quantized graviton modes. Within this common framework, the reduced dynamics of a
quantum harmonic oscillator exhibit a sharp structural contrast: a quantized graviton bath preserves coherence within the lowest
phonon-number
manifold, forming a protected sector at leading order, whereas a classical
stochastic GW field inevitably induces decoherence even inside this subspace. This difference provides an operational criterion for diagnosing the classical or
quantum nature of gravitational waves using mesoscopic optomechanical systems. Our results establish decoherence structure - not merely its magnitude - as a sensitive probe of gravitational quantumness and delineate the experimental regimes under which such tests may become feasible.
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All authors Partha Nandi, Sankarshan Sahu, Bibhas Ranjan Majhi, Francesco Petruccione
Materials Science
Margaret A. Anderson, Megan E. Goh, Yang Zhang et al. (+19 more)
The pyrochlore vanadates are compelling candidates for next-generation dissipationless devices. Lu2V2O7 and Y2V2O7 are
ferromagnetic insulators (Tc ~ 70 K) that are believed to exhibit the
magnon Hall effect and are expected to host topological
magnons. Their completely dissipationless
magnon edge states could be harnessed to realize low-power information transport in spintronic or magnonic devices. As a crucial step in the realization of devices, we synthesize the first thin films of pyrochlore Y2V2O7 on isostructural Y2Ti2O7 substrates and explore the
evolution of their
magnetic properties down to the ultrathin limit. All films are insulating ferromagnets with transition temperatures of up to the bulk value (Tc ~ 68 K) that decrease with thickness according to finite-size effects. Our films also exhibit a change in anisotropy from in-plane to out-of-plane easy axis coincident with the development of partial strain relaxation and nonzero
magnetic hysteresis in an applied field. This
evolution demonstrates the impact of strain on
magnetic anisotropy and paves the way to tunable
magnon topology.
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All authors Margaret A. Anderson, Megan E. Goh, Yang Zhang, Kyeong-Yoon Baek, Michael Schulze, Mario Brutzam, Christoph Liebald, Chris Lygouras, Dan Ferenc Segedin, Aaron M. Day, Zubia Hasan, Donald A. Walko, Hua Zhou, Peter Bencok, Alpha T. N'Diaye, Charles M. Brooks, Ismail El Baggari, John T. Heron, S. M. Koopayeh, Daniel Rytz, Christo Guguschev, Julia A. Mundy
Strongly Correlated Electrons
Coexisting Paramagnetic Spins and Long-Range Magnetic Order in Ba$_4$(Ru$_{0.92}$Ir$_{0.08}$)$_3$O$_{10}$
Farhan Islam, Jiasen Guo, Wei Tian et al. (+6 more)
We investigate the effect of dilute Ir substitution on the magnetism of the trimer-based ruthenate Ba$_4$Ru$_3$O$_{10}$ using
neutron diffraction,
magnetic susceptibility measurements, atomistic simulations, and first-principles calculations.
Neutron diffraction shows that Ir doping preserves the zigzag
antiferromagnetic structure and the ordered-moment magnitude of the parent compound, in which the moments reside exclusively on the two outer Ru(2) sites of each $\rm Ru_3O_{12}$ trimer, while the central Ru(1) site remains nonmagnetic. The Néel temperature is reduced from $\approx\!105$ K to 84.0(1) K upon 8% Ir substitution, while
magnetic susceptibility reveals a pronounced low-temperature Curie-like upturn, indicating the coexistence of paramagnetic
spins with long-range
antiferromagnetic order. Density-functional calculations shows that Ir preferentially occupies the central Ru(1) site, where its extended $5d$ orbitals disrupt the Ru-Ru molecular-orbital network and intra/inter-trimer exchange pathways. Atomistic simulations incorporating this paramagnetic dilution reproduce the suppressed ordering temperature and the coexistence of ordered and paramagnetic components.
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All authors Farhan Islam, Jiasen Guo, Wei Tian, Bing Li, Xudong Huai, Thao T. Tran, Gang Cao, Zachary Morgan, Feng Ye
Strongly Correlated Electrons
Charge-ordered states in twisted MoTe$_2$
Sparsh Mishra, Tobias M. R. Wolf and Allan H. MacDonald
We analyze interaction-driven charge-density-wave (CDW) states in the
spin-valley polarized first valence miniband of twisted MoTe$_2$ (tMoTe$_2$) using an adiabatic mapping from the continuum model to an effective Landau-level (LL) problem. When projected to the lowest LL, the leading spatial harmonic of the moiré-periodic potential changes sign at a magic twist angle $\theta_c$ where the band reaches its minimum bandwidth. By solving self-consistent Hartree-Fock equations in a multi-LL
Hilbert space, we find that triangular-
lattice CDW states with density maxima on MX (or XM) sites or on MM sites are favored on opposite sides of the magic angle at most filling factors and that stripe order appears near $\nu_h=1/2$. We show that CDW states at $\nu_h >1/2$ can carry a nonzero total Chern number, providing a natural route to reentrant integer
quantum Hall effects and discuss the energy competition between fractional Chern
insulator and CDW states.
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Strongly Correlated Electrons
The toric code under antiferromagnetic isotropic Heisenberg interactions
Won Jang, Robert Peters and Thore Posske
We investigate the impact of an isotropic
antiferromagnetic Heisenberg perturbation on the toric code, focusing on the resulting
quantum phase transition and the nature of the phase that emerges beyond topological order. Using neural-network
quantum states (NQS), we compute ground states over a wide range of Heisenberg couplings while fully respecting the exact
symmetries of the model. In the weak-coupling regime, the numerical results are in excellent agreement with an effective low-energy description derived from a Schrieffer-Wolff (SW) transformation, providing analytic control over the perturbative breakdown of topological order. We show that the Heisenberg perturbation only renormalizes local operators at low orders, whereas mixing between topological sectors occurs only at a perturbative order proportional to the system size. At intermediate values of the Heisenberg interaction, the topological phase breaks down. We estimate the critical point through a combination of the fidelity susceptibility and the logarithmic susceptibility of non-contractible Wilson loops for various system sizes. Furthermore, we utilize the topological
entanglement entropy to provide a comprehensive characterization of the phase transition. Beyond the transition, an
antiferromagnetic $\pm X/\pm Z$ Néel phase emerges, characterized by a fourfold-degenerate
symmetry-broken
manifold, which is explicitly probed using staggered-magnetization-based diagnostics. Our results show how local two-
spin interactions, which naturally arise in realistic implementations of the toric code, drive the breakdown of topological order. Moreover, we establish the SW approach as a systematic framework for analyzing such perturbations in combination with variational many-body methods.
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Materials Science
Active Learning for Tractable and Reproducible Pulsed Laser Deposition
Jackson S. Bentley, Christopher Rouleau, Ilia N. Ivanov et al. (+8 more)
This paper shows how data-driven machine learning approaches can improve growth control, reproducibility, and physical insight in the pulsed
laser deposition (PLD) growth of correlated
oxides. Despite well-known relationships between growth conditions and material properties, consistently producing high-quality films of complex materials like LaVO$_3$ remains difficult due to the highly non-
equilibrium nature of PLD and the defects and competing phases that accumulate during growth. Here, we use an active learning framework based on Gaussian process
Bayesian optimization that incorporates measured bulk and surface
lattice properties along with
impurity phase information to efficiently map the multidimensional growth space of LaVO$_3$ by PLD. By tuning the relative weighting of these properties, the model identifies an optimized region where phase-pure films of LaVO$_3$ exhibit two-dimensional surfaces, near-ideal
lattice parameters, and minimal sub-band gap optical absorption. The trained model reveals clear competition among different defect formation mechanisms that are connected to unseen parameters like supersaturation and surface mobility, thus giving insight into the highly non-
equilibrium process of PLD growth. Together, this demonstrates that property-guided machine learning can accelerate materials optimization while providing a new way to address fundamental growth mechanisms in PLD that enable understanding and utilization of
quantum phenomena found in complex
oxides.
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All authors Jackson S. Bentley, Christopher Rouleau, Ilia N. Ivanov, T. Zac Ward, Jiaqiang Yan, Anghea Dolisca, Rob G. Moore, Gyula Eres, Richard F. Haglund, Sumner B. Harris, Matthew Brahlek
Soft Condensed Matter
SAFT-P: A plaquette level perturbation for self-assembly in patchy colloids
Hamza Coban and Alfredo Alexander-Katz
We introduce SAFT-P, a plaquette-level extension of Statistical Associating Fluid Theory for patchy particles. By treating local clusters as associating superparticles and contracting their free energy back to monomer densities, SAFT-P retains information about patch
topology that is lost in conventional SAFT. Grand-canonical Monte Carlo simulations of binary and ternary mixtures show that SAFT-P captures
topology-dependent critical points and coexistence curves and discriminates between particles with identical valence but different patch layouts. Beyond
topology, incorporating plaquette-scale correlations also improves predictions in regimes where patch specific interactions are absent. Results indicate that resolving correlations at the plaquette scale provides an analytical route to model complex condensates and self-assembly with
topology-sensitive local structure.
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Statistical Mechanics
Operational Emergence of a Global Phase under Time-Dependent Coupling in Oscillator Networks
Veronica Sanz
Time-dependent coupling is often interpreted as introducing competition between a protocol rate and an intrinsic synchronization rate. We show that this interpretation is unavailable in the identical, overdamped Kuramoto model when time dependence enters only through a scalar multiplier of a fixed coupling field. The accumulated coupling $S(t)=\int_0^tK(u)\mathrm{d} u$ is then an exact dynamical clock: equal-exposure protocols traverse the same autonomous orbit, and integrable decays produce finite-exposure arrest rather than deterministic loss of adiabatic tracking. This clock suggests a classification under time reparametrization. Deterministic orbit observables and winding sectors are invariant; an additive perturbation $\varepsilon G$ has a leading response that is a linear functional of the reciprocal schedule $w(s)=1/K(t(s))$ against a kernel fixed by the autonomous orbit; and inertia or noncommuting graph generators lie outside this reciprocal-weighted class. Laboratory-time white noise has the corresponding $w$-weighted covariance. We derive exact mode covariances, prove a universal terminal bang–bang optimum under bounded coupling and fixed exposure, and validate both results in nonlinear networks. We also separate information in the full phase sample from information retained by the order parameter. Conditional observation error of $\arg Z$ follows a $1/(NR^2)$ law with a configuration-dependent prefactor, whereas a known-template experiment has Fisher information $N/\sigma^2$ independently of $R$; the efficiency of $\arg Z$ is $R^2/q_2$. Finally, periodic rings exhibit stable winding sectors with strong local but vanishing global order.
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Statistical Mechanics · Cross-listed from quant-ph
Classical Simulability from Operator Entanglement Scaling
Neil Dowling
Local-operator
entanglement (LOE) quantifies the nonlocal structure of Heisenberg operators and serves as a diagnostic of many-body chaos. We provide rigorous bounds showing when an operator can be well-approximated by a
matrix-product operator (MPO), given asymptotic scaling of its LOE $\alpha$-Rényi
entropies. Specifically, we prove that a volume law scaling for $\alpha\geq 1$ implies that the operator cannot be approximated efficiently as an MPO while faithfully reproducing all expectation values. On the other hand, if we restrict to correlations over a relevant sub-class of (ensembles of) states, then logarithmic scaling of the $\alpha < 1$
entropies implies MPO simulability. This result covers a range of relevant quantities, including infinite temperature autocorrelation functions, out-of-time-ordered correlators, and average-case expectation values over ensembles of computational basis states. Beyond this regime, we provide numerical evidence together with a random
matrix model to argue that this simulability result also typically holds for arbitrary states. Our results put on firm footing the heuristic expectation that a low operator
entanglement implies efficient tensor network representability, extending celebrated foundational results from the theory of
matrix-product states and providing a formal link between
quantum chaos and classical simulability.
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Soft Condensed Matter
Physics of active polymers: scaling analysis via a compounding formula
Takahiro Sakaue and Enrico Carlon
Active polymeric systems exhibit a rich spectrum of non-
equilibrium phenomena arising from
stochastic forces that explicitly break detailed balance. Despite the rapid growth of experimental and numerical studies, analytical progress remains limited. To date, theoretical understanding relies largely on variants of the active Rouse model, whose formal solutions, though exact, are often obscured by summations over Rouse modes and therefore provide limited direct physical insight. In this work, we develop a transparent scaling theory that captures the tagged-monomer mean-squared displacement (MSD) in active
polymers through a compounding formula: the MSD of a monomer in the chain is expressed as that of an isolated active particle, modulated by a connectivity factor encoding tension propagation along the
polymer backbone. This approach isolates the role of activity from that of
polymer connectivity and reveals the emergent dynamical regimes in a physically intuitive manner. We test the scaling predictions against exact calculations for a broad class of generalized active
polymer models driven by diverse noise statistics. The agreement demonstrates the robustness of the scaling framework across microscopic details. Our results provide a simple and extensible theoretical structure that can be applied to complex and analytically intractable active
polymer systems, thereby offering a unifying perspective on non-
equilibrium polymer dynamics.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Ramsey correlation spectroscopy with phase cycling using a single quantum sensor
Inbar Zohar, Santiago Oviedo-Casado, Andrej Denisenko et al. (+2 more)
Magnetic spectroscopy at the nanoscale provides unique insights into material properties and dynamics, with
quantum sensors like nitrogen-vacancy (NV) centers being ideally suited for these scales. However, detecting low-frequency signals remains a challenge due to finite coherence times ($T_2^*$), as signals oscillating slower than $1/T_2^*$ decay before sufficient phase accumulation occurs. We present RESOLUTE (Ramsey corrElation SpectroscOpy puLse seqUence wiTh phasE cycling), a protocol that overcomes these limitations by combining Ramsey measurements with correlation spectroscopy. By storing accumulated phase as a population imbalance during a correlation period ($T_\mathrm{corr} < T_1$) between two sensing periods, RESOLUTE generates an effective coherence time $T_2^p > T_2^*$. This shifts the frequency-matching condition to the correlation time, enabling detection in the previously inaccessible spectral region between $1/T_1$ and $1/T_2^p$. We experimentally demonstrate an extension of the effective coherence time from $T_2^* = 0.38\,\mu s$ to $T_2^p = 5.1\,\mu s$, surpassing Hahn Echo measurements. The technique successfully detects $^{13}$C
nuclear spin Larmor precession at fields as low as 49$\,$G ($\sim$50$\,$kHz). We further provide theoretical insight using Fisher information to characterize RESOLUTE's frequency estimation capabilities compared to existing protocols. Finally, by integrating adiabatic pulses and phase cycling, we demonstrate robust
spin control and effective DC signal extraction. These advancements provide enhanced sensitivity to weak dipolar interactions, essential for single-molecule imaging and
quantum sensing applications.
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All authors Inbar Zohar, Santiago Oviedo-Casado, Andrej Denisenko, Rainer Stöhr, Amit Finkler
Materials Science
New Crystal Structures Hide in Plain Sight: A Stress Test for AI-Guided Materials Discovery
Xin Zhang, Scott B. Lee, Sudipta Chatterjee et al. (+14 more)
New types of
crystal structures are discovered only rarely, and the artificial intelligence (AI) models now reshaping materials discovery have so far produced new chemical compositions within known structural families rather than genuinely new structures. We report GdNiSn4 and LuNiSn4, intermetallics that adopt a previously unreported structure type, found not by computation but by exploratory synthesis. Single-
crystal diffraction shows that the structure is an intergrowth of two known structural units. We then use this system as a
benchmark for two leading generative models, MatterGen and DiffCSP++. For DiffCSP++, the
benchmark is performed in its crystallographically constrained setting, using the required space-group and Wyckoff-position inputs. Under our sampling budget, neither model recovers the experimentally reported monoclinic structure within the structural-matching tolerance. The generated structures are evaluated without further structural relaxation using the nonmagnetic analog LuNiSn4, where we rule out 4f magnetism as the cause. Because the new structure is built from familiar building blocks, it should be derivable. We argue that encoding chemical
reasoning, such as the stacking of known motifs, is a concrete path toward AI that can discover structurally novel materials.
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All authors Xin Zhang, Scott B. Lee, Sudipta Chatterjee, Hanqi Pi, Yi Jiang, Fatmagül Katmer, Emily G. Ward, Daniel E. Widdowson, Charles C. Tam, Sarah Schwarz, Connor J. Pollak, Jaime M. Moya, Grigorii Skorupskii, Vitaliy A. Kurlin, Stephen D. Wilson, B. Andrei Bernevig, Leslie M. Schoop
Mesoscale and Nanoscale Physics
Ultra-slow orbital and spin dynamics in an electrically tunable quantum dot molecule
Christopher Thalacker, Michelle Lienhart, Markus Stöcker et al. (+13 more)
Tunnel-coupled optically active
quantum dot molecules (QDMs), have the potential to operate as
spin-
photon-interfaces with coupled
spins that interact with two different
photon frequencies at the same time. A prerequisite is to deterministically prepare two (electron or hole)
spins in the QDM and be able to electrically tune the orbital state couplings. Here, we demonstrate the sequential optical charging of a single QDM with two electron
spins while simultaneously maintaining the ability to widely tune orbital couplings using static electric fields and optically drive the system for
quantum light generation. We optically prepare one- and two-
spin states, initialize via optical pumping and explore orbital and
spin relaxation dynamics for one and two-
spin states as a function of the energy detuning and hybridization of orbital states. For two-
spin states, remarkably long S-T relaxation times are observed extending beyond $\sim 100\mu s$ with strong dependence on the relative energy of ground and excited two-
spin states. Qualitative agreement is observed with $\mathbf{k \cdot p}$ calculations of
phonon-mediated
spin-relaxation. Our results provide new quantitative understanding of the dynamics of one and two-
spin states and confirm their suitability of QDMs for creating multidimensional photonic cluster states by exploiting tunable
spin-
spin exchange couplings at zero
magnetic fields combined with optical driving.
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All authors Christopher Thalacker, Michelle Lienhart, Markus Stöcker, Nadeem Akhlaq, Irina Ivanova, Nikolai Bart, Arne Ludwig, Johannes Schall, Stephan Reitzenstein, Dirk Reuter, Steffen Wilksen, Christopher Gies, Krzysztof Gawarecki, Paweł Machnikowski, Kai Müller, Jonathan Finley
Superconductivity
Evolution of the Superfluid Density in Infinite-Layer Nickelates
Bai Yang Wang, Shannon P. Harvey, Kyuho Lee et al. (+6 more)
Nickelate
superconductors provide a valuable new platform for the study of unconventional superconductivity that is complementary to the cuprates. One of the central puzzles about high-temperature
superconductors is what factors determine the scale of their superconducting transition temperature ($T_\mathrm{c}$). To address this question for infinite-layer nickelates, we present a systematic mutual inductance study of the superfluid density across the doping-dependent superconducting dome of $\mathrm{Nd}_{1-x}\mathrm{Sr}_x\mathrm{NiO}_2$. We observe a weak superfluid stiffness that exhibits an approximately square-root correlation with $T_\mathrm{c}$. We also find a strong interplay between Nd magnetism and the superconducting phase, manifested as a substantial low-temperature suppression of superfluid density. These observations highlight the importance of superconducting phase fluctuations in limiting $T_\mathrm{c}$ and unexpectedly strong coupling between the Nd 4$f$ moments and the superfluid.
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All authors Bai Yang Wang, Shannon P. Harvey, Kyuho Lee, Yijun Yu, Yonghun Lee, Motoki Osada, Chaitanya Murthy, Srinivas Raghu, Harold Y. Hwang
Strongly Correlated Electrons
Fingerprinting fractons with pump-probe spectroscopy
Wei-En Tseng, Oliver Hart and Rahul Nandkishore
We demonstrate how pump-probe techniques enable specific spectroscopic diagnostics of fracton phases of matter by studying lineon-planon braiding in the paradigmatic X-cube model. Our discussion builds on previous works probing anyonic exchange statistics in conventional
spin liquids, but the extension to fracton phases reveals qualitatively new phenomena due to the restricted mobility of fractionalized excitations. A key feature is that nearby planons can form an emergent bound state by accessing different planes via alternative pairing configurations. We show that this bound state qualitatively modifies the long-time linear and nonlinear responses, leading to an asymptotic linear-in-$t$ behavior for the pump-probe signal $\chi_\mathit{ZZX}$. By contrast, swapping the pump and probe polarizations produces a nonlinear response $\chi_\mathit{XXZ}$ that is asymptotically $t$-independent. This asymmetry reflects the fact that the two species of fractionalized excitations live in different spatial dimensions. Thus, the pump-probe signals studied here are sensitive to (i) nontrivial braiding statistics in three dimensions, (ii) the existence of bound states among fractionalized excitations, and (iii) the one-dimensional mobility of lineons. Our results therefore provide spectroscopic signatures that distinguish fracton phases from conventional topologically ordered
spin liquids.
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Soft Condensed Matter · Cross-listed from physics.bio-ph
Shape-Independent Fluidity in Epithelial Cell Monolayers
Pradip K. Bera, Anh Q. Nguyen, Molly McCord et al. (+2 more)
Tissue fluidity regulates biological processes such as embryonic development, wound healing, and cancer metastasis. In confluent epithelia, where
cell packing fraction is effectively fixed, the prevailing paradigm postulates that fluidity is governed by a
geometric shape index determined by the balance of cortical tension and intercellular adhesion. Here, we report that reducing
cell-
cell adhesion triggers an increase in fluidity with no change in
cell shape index,
cell density, substrate traction, or junctional line tension. The observed decoupling of shape and fluidity reveals that current vertex models, which treat adhesion as contributing solely to interfacial tension, are incomplete. To reconcile these findings, we extend the theoretical framework to account for the dual nature of adhesion—its thermodynamic role in setting interfacial adhesion energy at the
cell-
cell junctions and its kinetic role in generating viscous drag due to relative motion between adjacent
cells. This generalized model quantitatively captures the experimental data, demonstrating that the interplay between adhesive energy and dissipative friction is essential for epithelial fluidity.
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All authors Pradip K. Bera, Anh Q. Nguyen, Molly McCord, Dapeng Bi, Jacob Notbohm
Quantum Gases
Core-bound waves on a Gross-Pitaevskii vortex
Evan Papoutsis, Nathan Apfel and Nir Navon
We find the dispersion relations of two elusive families of core-bound excitations of the Gross-Pitaevskii (GP)
vortex, varicose (axisymmetric) and fluting (quadrupole) waves. For wavelengths of order the healing length, these two families – and the well-known Kelvin wave – possess an infinite sequence of core-bound,
vortex-specific branches whose energies lie below the Bogoliubov dispersion relation. In the short-wavelength limit, these excitations can be interpreted as particles radially bound to the
vortex, which acts as a waveguide. In the long-wavelength limit, the fluting waves unbind from the core, the varicose waves reduce to
phonons propagating along the
vortex, and the fundamental Kelvin wave is the only core-bound
vortex-specific excitation. Finally, we propose a realistic spectroscopic protocol for creating and detecting the varicose wave, which we test by direct numerical simulations of the GP equation.
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