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Physics Condensed Matter

cond-mat Watch Condensed Matter

Friday 29 May

Superconductivity

Ni-O hybridization-driven electronic reconstruction across the superconducting dome in an infinite-layer nickelate

Chi Sin Tang, Shengwei Zeng, Xing Gao et al. (+11 more)

Superconductivity in infinite-layer nickelates has drawn wide interest as a cuprate analogue, yet how the electronic structure evolves with hole doping remains unsettled. Here we map the doping- and temperature-dependent unoccupied states of the La-based infinite-layer nickelate La1-xCaxNiO2 using O K-edge and Ni L-edge x-ray absorption spectroscopy. Superconductivity occurs for 0.18<=x<=0.27. Near x~0.20-0.23, low-energy spectral weight redistributes: Ni3d-dominated states decrease while O2p-hybridized states increase, indicating an orbital-selective crossover in Ni-O covalency. This crossover coincides with a sign reversal of the Hall coefficient and precedes the reduction of the superconducting critical temperature at higher doping. By directly linking transport anomalies and the superconducting dome to a measurable Ni-O orbital reorganization, our results provide a key step toward a unified, orbital-resolved phase diagram for infinite-layer nickelates and a practical route to engineer superconductivity via hybridization control.
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All authors Chi Sin Tang, Shengwei Zeng, Xing Gao, Zhaoyang Luo, Xiongfang Liu, Zhi Shiuh Lim, Saurav Prakash, Ping Yang, Caozheng Diao, Xinmao Yin, Changjian Li, Huajun Liu, Mark B. H. Breese, A. Ariando

Materials Science

Defect-engineered scaling of lead-free ferroelectrics with ultralow-voltage switching

Reza Ghanbari, Jiayue Wang, Harikrishnan KP et al. (+9 more)

Scaling ferroelectrics to nanometer thicknesses remains a central challenge for low-power, nonvolatile electronics, as leakage currents increasingly dominate with reduced dimensions. Alkali-based, lead-free ferroelectrics offer an environmentally sustainable alternative to lead-based systems, yet their scaling is severely limited by leakage arising from volatile alkali constituents. Here, we show that this intrinsic limitation can be transformed into an advantageous degree of freedom through defect engineering. By precisely modulating alkali deficiency during thin-film synthesis, we engineer clustered defect complexes that function as deep trap states, strongly suppressing leakage and enabling robust ferroelectric operation in ultrathin films down to the sub-10 nm regime at voltages below 100 mV. Our results establish defect-enabled scaling as a viable pathway for advancing environmentally benign ferroelectrics toward ultra-low-power, non-volatile electronic technologies.
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All authors Reza Ghanbari, Jiayue Wang, Harikrishnan KP, Zixiao Shi, Aarushi Khandelwal, Konnor Koons, Eli Rodrigues, Tao Zhou, Martin Holt, David A. Muller, Harold Y. Hwang, Ruijuan Xu

Mesoscale and Nanoscale Physics

Superconductor-"Metal" Transition of One-dimensional Interacting Bosons with Ohmic Quantum Dissipation

Miguel A. Cazalilla

The phase diagram of a system of interacting bosons (Cooper pairs) hoping on a one-dimensional (1D) lattice with onsite phase dissipation describing the Josephson tunneling to a nearby diffusive normal-metal electrode is studied. Starting from the system at commensurate lattice filling, it is shown by a combination of analytical techniques that the phase diagram contains two quantum phases: A dissipative Bose-Einstein condensate (D-BEC) or superconductor with long-range phase coherence, and a dissipative Mott insulator (D-Mott) or "metal" with exponentially decaying phase correlations in space and local imaginary-time correlations decaying as the local pairing correlations of the electrode. The D-Mott/metal phase can be described as a 1D array of dissipative boson puddles, weakly coupled by Josephson tunneling. The puddle size roughly corresponds to the length scale beyond which phase slips suppress phase coherence. The dissipative time-dependent Ginsburg-Landau theory phenomenologically used by Sachdev, Werner, and Troyer [Phys. Rev. Lett. 92 237003 (2004)] for the superconductor-metal transition in quasi-1D wires is derived from this microscopic puddle picture. Thus, the criticality of the D-Mott/D-BEC transition is shown to belong to the Wilson-Fisher universality class with dynamical exponent $z\approx 2$. At small doping, the D-Mott/metal phase remains stable due to its finite compressibility, which is computed to leading order in a perturbation expansion of the dissipation strength and the inter-puddle Josephson coupling. At larger doping, using a mapping to a pseudospin chain combined with bosonization, the D-BEC/superconductor phase is the ground state for non-vanishing but arbitrarily small dissipation. Similarities and differences with deconfinement transition of an array 1D bosonic Mott insulators in anisotropic optical lattices are also discussed.
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Materials Science

A Padding Method for Enhanced Encoding of Inorganic Structures with Varying Chemical Compositions

Thang Dang, Haderbache Amir, Tzanakakis Alexandros et al. (+1 more)

Designing novel inorganic materials through generative models remains an important challenge for material science, driven by the complexity and diversity of inorganic structures across expansive chemical compositions and structural landscape. The vast combinatorial space of inorganic compounds demands innovative, AI-driven approaches to overcome limitations in generative accuracy and efficiency. To address this, we introduce a novel method that redefines the encoding and generation of inorganic materials by utilizing domain-specific symmetry-aware representation. Our approach not only refines the representation of intricate inorganic structures but also contributes to the field of material discovery by enhancing the precision and stability of generated candidates. Central to our methodology is a novel padding technique that exploits crystal symmetry information to enhance the encoding process. By integrating Wyckoff position length-aware padding into an encoder architecture, we achieve a more robust informed representation of inorganic materials. This symmetry-driven enhancement improves deep learning models to generate stable, previously unexplored inorganic structures with superior accuracy and computational efficiency. Furthermore, we introduce an end-to-end system that leverages the machine learning potential models to seamlessly generate novel, even those unseen in the training data, and stable inorganic materials from initial data to validated output. This pipeline integrates advanced generative models with stability analysis, marking a significant leap forward in the automated exploration and design of next-generation inorganic materials. Our method improved reconstruction accuracy 5.3% in proton conductor data, and generated 63.5% more novel stable inorganic material to baseline model on the perov-5 dataset.
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All authors Thang Dang, Haderbache Amir, Tzanakakis Alexandros, Yoshimoto Yuta

Soft Condensed Matter

Tensor gradient flow for rod-like liquid crystals from molecular model with closure approximation by quasi-entropy

Yongyong Cai, Jie Xu and Haixin Zhang

In tensor dynamics for liquid crystals derived from molecular models, a common problem is closure approximation. For rod-like molecules, the Bingham closure has proved to outperform other methods because it inherits the gradient flow structure of the molecular model, but is difficult to achieve efficient computations maintaining the gradient flow structure. We propose a closure approximation by the quasi-entropy that has been successfully applied to the free energy, based on which we construct the tensor gradient flow. The quasi-entropy closure has the same symmetry properties as the Bingham closure. The resulting tensor gradient flow is able to constrain the eigenvalues of the tensor within the physical range, guaranteeing the positive definiteness of the dissipation operator given by the higher-order tensors. The quasi-entropy closure is easy to implement since it can be reduced to minimizing an elementary function of three variables. As a result, we construct a numerical scheme preserving the eigenvalue constraints and energy dissipation, with the closure approximation decoupled from solving the scheme. Numerical simulations are carried out for the interface between the isotropic and the uniaxial nematic phase, as well as the defect evolutions, where the higher-order tensors indeed make a difference.
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Materials Science

A Convenient Sealing Method Using Boron Nitride Capping for Reactive Reactions

Boqin Song and Tianping Ying

While quartz (SiO2) ampule sealing is commonly used in laboratories to prevent sample oxidation during synthesis, its application is limited for reactions involving highly reactive elements such as alkali, alkaline-earth, and rare-earth metals. These elements can react with SiO2 at elevated temperatures, causing compositional loss, tube failure, and experimental inconsistencies. Here, we introduce an inexpensive boron nitride (BN) cap sealing technique. This approach is readily adaptable to centrifugal separation and flux transport growth and yields superior sample quality. We demonstrate its efficacy by growing KFe2As2 and CsCr6Sb6 single crystals, the former exhibiting record-high quality, with a residual resistivity ratio (RRR) exceeding 2500, and the latter achieving significantly larger crystal dimensions than other methods. This accessible and economical method promises to accelerate the discovery of novel materials that contain reactive elements.
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Strongly Correlated Electrons

Non-Perturbative Renormalization Group for Ising-Nematic Criticality: A Closed-Form Nonlocal Ansatz

Hyeon Jung Kim, Kyoung-Min Kim and Ki-Seok Kim

The two-dimensional metallic quantum critical problem is a long-standing puzzle that is widely believed to hold the key to resolving ubiquitous non-Fermi liquid behavior in strongly correlated electronic systems. In this study, we present a non-perturbative renormalization group (RG) analysis of the metallic Ising-nematic quantum critical point in two dimensions, formulated directly around an intrinsically nonlocal infrared (IR) boson propagator. Rather than treating the anomalous dynamical critical exponent $a$ as a fixed phenomenological parameter, we regard it as an intrinsic component of the fixed-point data to be determined from the internal consistency of the low-energy patch field theory under highly anisotropic scaling dimensions ($[k_0]=a+1$, $[k_x]=2$, $[k_y]=1$). While the leading two-loop diagrammatics vanish identically due to kinematic pole configurations, our three-loop evaluation reveals a profound structural asymmetry between the sectors: the fermion self-energy and Yukawa vertex receive non-vanishing logarithmic corrections, whereas the corresponding bosonic counter-term remains strictly zero. Consequently, we find that no self-consistent, intersecting fixed-point solution for the exponent $a$ exists within the three-loop truncation, failing to reproduce the physical value of $a \approx 1.85$ observed in quantum Monte Carlo simulations. We conjecture that the cross-linked topology of the four-loop boson self-energy diagrams is exactly marginal and yields the minimal, mandatory bosonic counter-term required to restore multi-sector self-consistency. Our framework establishes a rigid multi-loop matching scheme necessary to uniquely pin down the critical exponent, and uncovers a stable phase space for field anomalous dimensions.
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Other Condensed Matter

Nonlinear Schrodinger Equations for Dense Bose Fluid and He4 Film at Low Temperatures

Vladimir I. Kruglov

We have derived the nonlinear Schrodinger equation generalizing the Gross-Pitaevskii (GP) equa tion for dilute Bose gas. The derivation is based on the Hartree-Fock time-dependent mean-field theory with an arbitrary intermolecular interaction potential. It is shown that obtained nonlinear Schrodinger equation with appropriate redefinition of coefficients can be used for description of dense Bose fluid at low temperatures. We also present the Schrodinger type equation describing the superfluid component of helium in two fluid hydrodynamics. This approach leads to quantum correction for superfluid component of velocity in two fluid hydrodynamics. We also have derived the nonlinear Schrodinger equation for superfluid He4 film at low temperatures. It is shown that this Schrodinger type equation for superfluid He4 film leads to phonon-roton dispersion relation for elementary excitation at low temperatures.
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Statistical Mechanics · Cross-listed from physics.ao-ph

A mathematical framework for dynamic emergent constraints in climate science

Francesco Ragone and Valerio Lucarini

Emergent constraints in climate science are empirical relations that link the response to a forcing of a physical observable to the properties of other observables, with the aim of reducing climate change projection uncertainties. Here we use recent results in linear response theory to develop a mathematical framework for dynamic emergent constraints, a class of emergent constraints linking the response of different observables to the same forcing. We show how traditional dynamic emergent constraints are a special case of more general relations, that we call integral dynamic emergent constraints. These relations allow to compute the response of a predictand as the convolution of the response of a predictor and the proxy Green's function of the predictand-predictor pair. The conditions for the existence of integral emergent constraints are related to the causality of the proxy Green's function and the time scales at which the system is observed. We apply this framework to global warming simulations with the MPI-ESM climate model, to study dynamic emergent constraints between different observables. These results allow to put the theory of dynamic emergent constraints on firm mathematical ground, and suggest a protocol to identify necessary conditions for the existence of such relations in climate data.
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Materials Science

Simulations of dislocation dynamics on an atomic lattice: the effect of collision rules

Tom Hudson, Akaraphon Jantaraphum and Patrick van Meurs

The stochastic dynamics of dislocations on a one-dimensional periodic lattice domain are considered. Two models are studied: one without a collision rule, and one which annihilates colliding dislocations if they have opposite orientation. The behaviour of both models is investigated by means of a series of numerical simulations exploring the asymptotic behaviour of these models as the number of dislocations increases. From these simulations, evidence is obtained that the discrete model with annihilation tends to a PDE for the dislocation density that accounts for annihilation. However, the discrete model without a collision rule does not appear to exhibit consistent convergence behaviour; instead, it appears that the expected PDE with conserved dislocation density appears in the limit for some parameters, but that for other parameters the density appears to follow to the evolution of the PDE with annihilation. These findings provide evidence that a careful treatment of dislocation collisions is important in discrete dislocation dynamics models.
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Thursday 28 May

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

Collective Emission in LH2 Assembly Beyond the Point-Dipole Approximation

Javed Akhtar and Himangshu Prabal Goswami

Collective emission in light-harvesting assemblies is governed by the local transition dipole and finite geometry of emitting units, a fact that point-dipole approximation obscures. To go beyond this picture, we develop a non-Hermitian Hamiltonian using the quantum electrodynamic dyadic Green's tensor for a purple bacteria. We construct it for the isolated 24-bacteriochlorophyll conical frustum and its P42$_1$2 crystallographic assembly. The P42$_1$2 unit-cell symmetry is found to invert the bright-dark ordering of the single ring, placing subradiant states at the low-energy end and revealing the entire crystal to be the energy-harvesting entity. Tilt-driven switching is activated only in crystal geometries where the finite dipole-carrier (LH2) lies perpendicular to the growth plane. Vacancy and orientational disorder work only in cooperation to renormalize the switching threshold from higher polar angles to lower values.
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Soft Condensed Matter

Forman–Ricci Curvature for Irregular Convex Mosaics

Abhyudaya Gupta, Sayak Mukherjee and Kuldeep Saha

Forman has defined a discrete version of the Ricci curvature on Riemannian manifolds, known as the Forman–Ricci curvature. The Forman–Ricci curvature has found significant applications in several pattern recognition problems occurring in natural sciences. Domokos and Langi, on the other hand, have defined a notion of irregularity for convex mosaics, which has also found remarkable applications to the geological problem of fractures in rocks. We define a modification of the classical Forman–Ricci curvature for irregular convex mosaics and demonstrate how they can be used to distinguish between various fractures or cracking patterns appearing in nature.
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Soft Condensed Matter

Wetting as an emergent property of water: reformulating Young equation on molecular grounds

Nicolas Loubet and Gustavo Appignanesi

Young equation provides a remarkably successful macroscopic description of wetting, yet its molecular origin (particularly for water) has remained elusive for over two centuries. Here we make the molecular basis of aqueous wetting explicit by reformulating it in terms of a molecular wetting coefficient, omega m, which quantifies how an interface compensates the intrinsic energetic cost of hydrogen-bond defects relative to bulk water. Across a broad and continuous spectrum of hydrophilicities, spanning chemically diverse experimental and model surfaces, macroscopic contact angles collapse onto a single universal master curve when expressed through omega m. This molecular reformulation closes Young and Young-Dupre relations on energetic grounds, establishing a unified and predictive physical link between wetting, adhesion, cavitation, and nanoconfined filling. By anchoring interfacial behavior to waters intrinsic hydrogen-bond energetic scales, our results reveal wetting as an emergent property of water itself, rather than a surface-specific attribute and provide a transferable molecular framework that recalibrates energetic intuition and guides the rational design of aqueous interfaces. (This document is the unedited Author version of a Submitted Manuscript subsequently accepted for publication in J. Am. Chem. Soc. For the published version, which includes a more complete molecular-thermodynamics grounding of the method see the published version)
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Statistical Mechanics · Cross-listed from math.PR

Search at bounded speed with immigration

Hwai-Ray Tung and Sean D Lawley

Many biophysical search processes employ searchers which enter or "immigrate" into the domain progressively over time. Existing search time estimates can become unphysical for fast immigration since they imply that searchers move at infinite speed. In this paper, we investigate search times of immigrating searchers that move at bounded speed. In the fast immigration limit, we determine the full probability distribution and all the moments of the $k$th search time in terms of the early time probability distribution of a single searcher. We apply these rigorous mathematical results to several canonical models of stochastic search. We further analyze different models of "diffusion" and use these results to investigate when and how the minutiae of searcher dynamics affect search times. We compare our theory to numerical simulations.
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Materials Science

Deterministic fabrication of large-area, high-crystallinity oxide moire superlattices

Reza Ghanbari, Eli Rodrigues, Young-Hoon Kim et al. (+10 more)

Oxide twistronics extends moire engineering beyond van der Waals materials, offering a promising platform for accessing emergent interfacial phenomena arising from the strong coupling of lattice, charge, and orbital degrees of freedom in complex oxides. However, deterministic fabrication of high-crystallinity oxide moire superlattices over large lateral dimensions remains challenging due to the three-dimensional bonding network of oxides. Here, we demonstrate a scalable, generalized fabrication strategy that enables the formation of high-crystallinity oxide moire superlattices with clean, chemically bonded interfaces and precisely controlled twist angles down to nominal values of 0.1 degree, achieving sub-degree twist-angle accuracy across large contiguous lateral dimensions approaching the millimeter scale. Using NaNbO3 as a model system, we show that the resulting interlayer coupling drives pronounced structural reconstruction that modifies both the phase structure and ferroelectric domain configuration. Synchrotron-based X-ray 3D reciprocal space mapping reveals the emergence of a single-phase state in twisted bilayers, in contrast to the mixed-phase structure observed in single-layer membranes prior to twist assembly. The structural signatures are further consistent with gradual lattice rotation distributed along the thickness direction that may accommodate interfacial shear strain, distinct from reconstruction observed in van der Waals moire systems, which primarily occurs through in-plane stacking rearrangement. This collective lattice response is correlated with twist-dependent nanoscale electromechanical modulations observed by piezoresponse force microscopy. These results establish a scalable materials platform for oxide twistronics and open new pathways towards integrating twist-engineered complex oxides into practical, macroscale device architectures.
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All authors Reza Ghanbari, Eli Rodrigues, Young-Hoon Kim, Konnor Koons, Yan Li, Kabelo Lebogang, Yiming Ding, Doug Barefoot, Yueyin Wang, Yin Liu, Hua Zhou, Miaofang Chi, Ruijuan Xu

Materials Science

Symmetry-Resolved Second Harmonic Generation in Quantum and Functional Materials

Xiaoyu Guo, Chang Jae Roh and Youngjun Ahn

Second harmonic generation (SHG) has evolved from a probe of noncentrosymmetric crystals into a symmetry-resolved optical method for identifying order parameters in quantum and functional materials. In particular, polarization-resolved rotational anisotropy (RA) measurements of SHG can connect nonlinear susceptibility tensors to the crystallographic and magnetic point groups of the underlying materials. This capability is especially powerful when the ordered state is weak, spatially confined, multipolar, magnetic, or hidden from conventional linear probe techniques. In this review article, we established a systematic symmetry-based framework for understanding RA-SHG and provide a comprehensive overview of RA-SHG studies across a broad range of condensed matter systems. We begin with basic theoretical background for the multipole origins of SHG radiation, the construction of nonlinear susceptibility tensors, and a group-theoretical framework connecting tensor components to order parameters. We then review the applications of RA-SHG to polar materials, magnetic orders, and other hidden electronic orders. Finally, we outline challenges and future research directions for using SHG to reveal, image, and control hidden, intertwined, and nonequilibrium phases in quantum and functional materials.
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Materials Science

Observation and Control of the Magnetic Photogalvanic Effect from Strongly Bound Excitons

Xianfan Nie, Tarun Patel, Hyunggeun Lee et al. (+11 more)

Photogalvanic effects arising from the quantum geometry of noncentrosymmetric materials are promising for next-generation light-harvesting devices that do not require a built-in electric field. Recent theories predict photogalvanic currents generated in magnetic systems with spin-dependent symmetry breaking as well as by bound exciton states, allowing for potential magnetic field control of the photoresponse and enhanced detection of deep sub-gap signals, respectively. We demonstrate the magnetic photogalvanic effect in a bilayer CrI3 tunnel junction with both magnetic field switching and electric field tuning of interlayer symmetry. By controlling for the polarization and energy of light illumination, we disentangle the shift and injection current contributions and find that the peak response occurs under resonant excitation of strongly bound excitons in CrI3. Our results can be captured within a many-body framework of the photogalvanic effect, while our devices function as tunable, multispectral helicity- and polarization-sensitive detectors that highlight the potential of 2D magnets for future optoelectronic applications.
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All authors Xianfan Nie, Tarun Patel, Hyunggeun Lee, Chuangtang Wang, Meixin Cheng, Mingrui Lai, Bowen Yang, Matteo Pennacchietti, Shiyu Liu, Hechang Lei, Liuyan Zhao, Michael E. Reimer, Su Ying Quek, Adam W. Tsen

Quantum Gases

Entanglement entropy of an acoustic black hole

P.C. van de Graaf and H.T.C. Stoof

We introduce a method to numerically compute the entanglement entropy of an acoustic black hole. It is shown that the entanglement entropy of sufficiently large subregions scales linearly with size and thus shows a volume law instead of an area law. The origin of this scaling can be traced back to the non-separable long-distance correlations due to the production of phonon pairs at the horizon. The system is shown to be locally thermal, such that the part of the entanglement entropy scaling with volume is well approximated by the thermal entropy of the outgoing Hawking radiation.
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Materials Science

A new Fermi kinetic phase transition model for metals including hysteresis effects

Ann E. Mattsson Wills, Daniel N. Blaschke, Michael B. Prime et al. (+3 more)

We present a new phenomenological model for phase transformation (PT) kinetics in metals, the "Fermi Kinetic Phase Transition (KPT) Model". It is designed such that it captures the main macroscopic features of our previously developed micro-structure dependent model, but at a fraction of the computational cost of the latter. Using four model parameters, the Fermi KPT model performs better than other phenomenological PT kinetics models in the literature, as shown by our present comparisons to experimental data for iron and tin.
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All authors Ann E. Mattsson Wills, Daniel N. Blaschke, Michael B. Prime, David R. Jones, Saryu Fensin, Abigail Hunter

Materials Science

Harnessing diamond surface features for dense and aligned NV ensembles

Eveline Postelnicu, Lillian B. Hughes Wyatt, Tri Nguyen et al. (+6 more)

Controlling nitrogen doping in diamond is key to advancing nitrogen-vacancy (NV) center devices. We harness the hillock, a typically undesirable surface feature, to incorporate high densities of grown-in, aligned NV-centers on a (001)-oriented substrate. Enhanced cathodoluminescence at hillock sidewalls is correlated via nanoSIMS to up to 1000x greater nitrogen incorporation compared to the planar film. We find that these hillocks are associated with stacking faults and edge-type dislocations, consistent with an origin in surface preparation rather than substrate screw dislocations. Yet, the growth is orderly enough that each of the four hillock sidewalls hosts a distinct NV orientation. A 1.7-2% grown-in NV/substitutional nitrogen (P1) ratio, 4x higher than typical (001)-oriented growth, is measured via NV decoherence analysis. By revealing that spontaneously formed hillocks act as natural laboratories for dense, aligned NV formation, this work motivates systematic investigation of facet-dependent nitrogen incorporation and preferential NV alignment in (001) diamond.
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All authors Eveline Postelnicu, Lillian B. Hughes Wyatt, Tri Nguyen, Simon A. Meynell, Christine Jilly, Paul Wallace, Andrew Barnum, Ania Bleszynski Jayich, Kunal Mukherjee

Soft Condensed Matter

Mean-squared displacements of rough particles in polydisperse granular gases

Anna S. Bodrova

We investigate the diffusion coefficients and mean-squared displacements in a polydisperse granular gas in a homogeneous cooling state by considering the roughness of the particles. We study their dependence on the normal and tangential restitution coefficients. We show that the motility of particles is strongly affected by their mechanical properties and surface characteristics.
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Superconductivity · Cross-listed from quant-ph

Dually tunable YBCO coplanar waveguide resonators based on helium-ion-generated Josephson inductances

Kenny Fohmann, Timo J. Glebe-Märklin, Benedikt Wilde et al. (+5 more)

Superconducting microwave circuits with and without Josephson inductances are the Swiss Army knife for many experiments and technologies from quantum information science to astrophysical particle detectors. Despite a large variety of existing circuit types, thin film materials and Josephson junction technologies, a flexible and reliable platform for high-magnetic-field and high-temperature applications is yet to be found. In this manuscript, we investigate coplanar waveguide cavities made of the high-temperature cuprate superconductor YBa$_2$Cu$_3$O$_7$ (YBCO), integrated with Josephson inductances and quantum interferometers that are generated by the controlled local irradiation of the YBCO with a focused helium ion beam. We obtain strongly flux-tunable microwave resonators, which not only display periodic interferometer oscillations of resonance frequency and decay rate, but also a superimposed Fraunhofer-like modulation pattern. The latter originates from the magnetic field tuning of the individual Josephson junction critical currents due to the out-of-plane junction barriers. It allows adjusting resonance frequency and flux responsivity independently of each other, potentially enabling tunable microwave circuits with low sensitivity to external magnetic-field noise over a broad range of frequencies. Finally, we investigate the temperature dependence of the cavities, show that they have promising characteristics up to 14$\,$K, and present a model for the junction-induced cavity losses.
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All authors Kenny Fohmann, Timo J. Glebe-Märklin, Benedikt Wilde, Mohamad Kazouini, Christoph Schmid, Dieter Koelle, Reinhold Kleiner, Daniel Bothner

Strongly Correlated Electrons

Topological Phenomena Protected by Diabolical Textures

Sayantan Mandal, Neelima Pulletikurty and Abhishodh Prakash

We present a new class of topological phenomena in inhomogeneous systems arising from the adiabatic spatial embedding of parametrized families of quantum states such as charge pumps and their generalizations. We demonstrate that each topologically distinct class of these “diabolical textures" gives rise to distinct gapped states that are separated by “trap-scaling" critical points, defect transitions, or intervening phases. Their phase diagrams exhibit versions of “unnecessary criticality” and “multiversality,” within a noninteracting setting. We demonstrate this in a one-dimensional Thouless pump texture trapping a charge and a two-dimensional class D texture trapping a Kitaev chain, including an analysis of their stability under weak symmetry-preserving perturbations and interactions. For systems in arbitrary spatial dimensions and global symmetries, we present a framework to systematically classify diabolical textures using Kitaev's $\Omega$ spectrum conjecture.
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Soft Condensed Matter · Cross-listed from astro-ph.IM

Experiments on Settling of Granular and Cohesive Material in Low Gravity

Matthias Keulen, Timo Giese, Kolja Joeris et al. (+1 more)

The regolith of rocky bodies, such as planets or asteroids, generally settles under gravity conditions different from those of Earth. The behavior of granular material is not easily scalable for different gravities. To predict these highly complex systems where cohesive inter particle forces can be comparable to gravitational forces, we need simulations and experiments. We did experiments on settling of three different granular samples in varying reduced gravities and examined their packing densities. We used a high precision linear stage to artificially induce reduced gravities inside the zero $g$ environment provided by the ZARM drop tower and observe the settling of our samples. The three samples were fine basalt with particle diameters of $1\text{-}200\,\mu$m, coarse basalt with $2\text{-}5\,$mm and glass beads with $750\text{-}1000\,\mu$m. The artificial gravities were $150,\,250,\,500,\,750$ and $1000\,$mm/s$^2$ and therefore ranged from large asteroid gravity to almost moon gravity. We saw the granular samples have higher volumes in lower gravities and therefore lower packing densities, we also saw the fine basalt be the most sensitive to changes in gravity, up to $+19.6\,\%$ in volume for $250\,$mm/s$^2$, followed by the coarse basalt particles, up to $+12.2\,\%$ for $150\,$mm/s$^2$ and the glass beads packing density being the least sensitive to changes in gravity, up to $+4.25\,\%$ for $250\,$mm/s$^2$. With these experiments we show change in volume is not solely dependent of particle size but also roughness and uniformity, we provide real life experimental data to validate theoretical works and highlight the role of cohesive forces in low gravity environments.
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All authors Matthias Keulen, Timo Giese, Kolja Joeris, Jonathan Kollmer

Mesoscale and Nanoscale Physics

Visualizing orbital magnetism in electron doped rhombohedral multilayer graphene

Owen I. Sheekey, Trevor B. Arp, Benjamin A. Foutty et al. (+24 more)

Electron doped rhombohedral multilayer graphene at high displacement field features an exceptionally flat band minimum with near-ideal quantum geometry. Experiments in this regime observe the formation of a 'quarter metal,' in which the electron liquid condenses into a single spin- and valley flavor. Remarkably, recent experiments have found a zero resistance state in the same region of the density- and displacement-field-tuned parameter space, attributed to the formation of a chiral superconductor from an orbitally ferromagnetic normal state. Here, we use nanoSQUID-on-tip magnetometry to map the orbital magnetization of electron-doped rhombohedral graphene devices ranging in thickness between 3 and 15 layers. Magnetization within the quarter metal phases peaks at finite density, consistent with concentration of the Berry curvature in a finite-momentum 'ring of fire'. Correlating transport and local magnetometry data in a superconducting tetralayer sample reveals a finite orbital ferromagnetic moment, providing direct evidence of valley polarization in the superconducting ground state. We further show that widely observed stochastic switching of the resistivity in both metallic and superconducting regimes arises from a density-tuned sign change in the valley-resolved total magnetic moment. This leads to the formation of metastable magnetic domains under typical gate control sequences and can also be harnessed for electric-field controlled switching of the magnetization across the entire device. Finally, high resolution measurements of the magnetization across a superconducting transition allow us to put an upper bound on the 'condensation magnetization' of 0.1 Bohr magneton per carrier, placing a strong quantitative restriction on theoretical models for ferromagnetic superconductivity.
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All authors Owen I. Sheekey, Trevor B. Arp, Benjamin A. Foutty, Ruoxi Zhang, Tixuan Tan, Ludwig F. W. Holleis, Yi Guo, Sandesh S. Kalantre, Canxun Zhang, Mark Zakharyan, David Gong, Aidan Keough, Youngjoon Choi, Ysun Choi, Siyuan Xu, Tian Xie, Ben Hodder Alexander, Marisa Hocking, Qingrui Cao, Martin E. Huber, Takashi Taniguchi, Kenji Watanabe, Chenhao Jin, Etienne Lantagne-Hurtubise, Aaron Sharpe, Trithep Devakul, Andrea F. Young

Mesoscale and Nanoscale Physics · Cross-listed from quant-ph

Quantum Desynchronization of Limit Cycles

Hans Christiansen and Jens Paaske

It is well known from classical physics that weakly coupled self-sustained oscillators may spontaneously lock their phases. Just like classical synchronization is known to break down due to noise induced phase slips, we show here how the synchronization of continuous variable quantum systems breaks down by proliferation of quantum phase slips. Within a Keldysh path integral formulation of limit cycles, we analyze the phase dynamics and show how, in spite of strong phase correlations, quantum phase slips degrade the actual phase locking. This approach also allows us to address non-Markovian effects on the synchronization of limit cycles, which we illustrate explicitly for superconducting resonators coupled via a voltage biased double quantum dot.
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Superconductivity

Electron Doping of $\mathrm{La_3Ni_2O_7}$ Thin Films: Candidate Metal Dopants and Their Potential Impact on Superconductivity

Shi-Cong Mo and Wéi Wú

The bilayer Ruddlesden-Popper nickelate $\mathrm{La_3Ni_2O_7}$ has emerged as a promising platform for exploring and understanding high-temperature superconductivities. While existing doping studies have primarily concentrated on hole doping achieved through strontium substitution or oxygen content tuning, the electron-doped regime in this system remains largely unexplored. In this work, we systematically investigate possible electron doping in $\mathrm{La_3Ni_2O_7}$ thin films through tetravalent element substitution, employing first-principles density functional theory calculations. Our results suggest that $\mathrm{cerium}$ (Ce) doping is inefficient in introducing electron carriers into the low-energy bands. In contrast, zirconium (Zr), hafnium (Hf), and thorium (Th) emerge as efficient electron donors. We show that Zr and Hf doping preferentially introduce electrons into the $d_{x^2-y^2}$-derived bands, while Th doping delivers more electrons into the $d_{z^2}$-derived bands. Electron dopings notably augment the interlayer hopping $t_{\perp}$ between $d_{z^2}$ orbitals, which could enhance superexchange coupling $J_{\perp}$ and consequently promote an increase in superconducting $T_c$. We evaluate the Coulomb interaction parameters using constrained random phase approximation. Our results identify viable dopants for achieving electron-doped $\mathrm{La_3Ni_2O_7}$, which not only diversifies the material family but also provides new platforms for disentangling the origins of $\mathrm{La_3Ni_2O_7}$ superconductivity.
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Strongly Correlated Electrons

Spectroscopic evidence for a molecular orbital Kondo insulator

Ke-Jun Xu, Kuan H. Hsu, Nathan Giles-Donovan et al. (+13 more)

A Kondo insulator (KI) is a prototypical example of a highly entangled phase of matter, where many-body interactions between local moments and delocalized electrons engender the non-magnetic insulating ground state. Conventionally, the local moments arise from atomic multiplet states with a narrow bandwidth, limiting Kondo coherence to low temperatures. Here, we realize a new paradigm for constructing the KI state with hybridized molecular orbitals in FeSb2. Resonant inelastic X-ray scattering (RIXS) at the Fe L-edge reveals distinct signatures of band-like continuum states and localized states. Comparisons with first-principles calculations establish a mixed-configuration ground state with hybridized Fe d-Sb p molecular orbitals as basis states. By systematically investigating the RIXS momentum, temperature, and doping dependences, we find propagating collective modes commensurate with many-body charge and spin excitations. Our results pave the way for understanding the emerging class of unconventional d electron insulators and engineering high temperature Kondo many-body states.
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All authors Ke-Jun Xu, Kuan H. Hsu, Nathan Giles-Donovan, Christopher T. Parzyck, Gi-Hyeok Lee, Wanli Yang, Jun Okamoto, Hsiao-Yu Huang, Di-Jing Huang, Joshua J. Kas, John Vinson, Zhi-Xun Shen, Dung-Hai Lee, Thomas P. Devereaux, Wei-Sheng Lee, Robert J. Birgeneau

Mesoscale and Nanoscale Physics · Cross-listed from quant-ph

Quantum Synchronization of Fock States

Fabian Hassler, David Scheer, Samah Saquaque et al. (+1 more)

Synchronization, a ubiquitous phenomenon in classical systems, has recently been extended to the quantum domain. Here, we show quantum synchronization of a bosonic mode exhibiting a Fock state-like limit cycle, manifesting as a steady state with a negative Wigner function. We demonstrate that this non-classical state can be phase-locked to an external drive, achieving synchronization within an Arnold tongue regime. We argue that synchronization is a dynamical property and fundamentally tied to the suppression of phase slips, which we show to occur with exponentially decreasing probability. We introduce a novel method to extract the phase slip rate from the Lindblad time evolution of the system. This work opens new avenues for understanding and manipulating non-classical synchronization dynamics.
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All authors Fabian Hassler, David Scheer, Samah Saquaque, Steven Kim

Materials Science

Exploring the Origins of Anti-Ambipolarity in BBL Polymer: Links to Redox Chemistry, Electronic Structure, and Structural Dynamics

Maryam Ghotbi, Alejandro Aviles and Perla B. Balbuena

We examine the intrinsic physical-chemical properties of the conjugated ladder-type polymer poly(benzimidazobenzophenanthroline) (BBL) in response to electron transfer. We aim at explaining the origin of the anti-ambipolar behavior behind the observed BBL nonlinear response associated with specific device architectures. To elucidate this point, we use theory and computation based on first principles, including density functional theory optimizations, ab initio molecular dynamics, time-dependent DFT, and Marcus-theory analysis. Our results reveal that this redox response is not simply monotonic but follows an alternating odd/even pattern in which gap narrowing and reopening occur sequentially before near-gapless behavior emerges at high charging. Converging theoretical evidence in this work demonstrates that bell shaped conductivity in BBL originates in its fundamental electronic structure and supramolecular organization.
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