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Physics Condensed Matter

cond-mat Watch Condensed Matter

Thursday 25 December

Mesoscale and Nanoscale Physics

Giant universal conductance fluctuations in the antiferromagnetic topological insulator MnBi2Te4

Michael Wissmann, Joseph Dufouleur, Louis Veyrat et al. (+4 more)

Intrinsic magnetic topological insulators can host quantum states with quantized magneto-electric responses, such as the axion and Chern insulators states evidenced in ultra-thin MnBi2Te4 films. Yet, whereas quantization is investigated thoroughly, transport properties related to the phase of charge carriers remains unexplored. Here, we study quantum coherent transport in mesoscopic Hall bars fabricated from thick exfoliated MnBi2Te4 flakes, and reveal the longest phase-coherence length ever observed in a mesoscopic magnet (about 500nm at 1K), associated to 2D topological surface states. In the fully-coherent regime, significant non-local contributions to quantum interference up to the micron scale lead to giant-amplitude universal conductance fluctuations (about 20e2/h). In the self-averaging regime, the statistical properties of conductance fluctuations confirm the 2D nature of quantum interference and different dephasing mechanisms are identified, as due to either magnetism or magnetic flux through coherent loops. Remarkably, the weak decoherence in magnetic topological insulator nanostructures show their potential to realize novel quantum spin interferometers based on dephasing by local magnetic textures at liquid-helium temperatures.
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All authors Michael Wissmann, Joseph Dufouleur, Louis Veyrat, Anna Isaeva, Laurent Vila, Bernd Büchner, Romain Giraud

Materials Science

Hidden layered structures from carbon-analog metastability in metal dichalcogenides

Shota Ono

Carbon exhibits both a layered ground state structure that produces two-dimensional (2D) nanosheets and a non-layered diamond structure created under high pressure conditions. Motivated by this metastability relationship, we revisit the ground state structure of metal dichalcogenides that are known to have non-layered pyrite-type structure. Ultrathin films of pyrite-type ZnSe$_2$ spontaneously transform into a layered phase. This phase is identified as a ground state, and the monolayer exhibits strong elastic anisotropy and a semiconducting bandgap larger than that of the pyrite phase by a factor of two. We demonstrate that a two-valued but directional potential energy surface exists along a Bain-like distortion path, hiding the layered ground state. This work implies that many 2D materials are hidden in non-layered materials and connects 2D materials science with surface and high-pressure science.
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Wednesday 24 December

Statistical Mechanics

Feedback Driven Convergence, Competition, and Entanglement in Classical Stochastic Processes

Allen Lobo and Saravanan A

We present a dynamical theory of statistical convergence in which the law of large numbers arises from outcome-outcome feedback rather than assumed independence. Defining the convergence field and its derivative, we show that empirical frequencies evolve through coupling, producing competition, finite-m fluctuations, and classical entanglement. Using the Kramers-Moyal expansion, we derive an Ito-Langevin and Fokker-Planck description, reducing in the symmetric regime to a time-dependent Ornstein-Uhlenbeck process. We propose variance-based witnesses that detect outcome-space entanglement in both binary sequences and coupled Brownian trajectories, and confirm entanglement through numerical experiments. Extending the formalism yields multi-outcome feedback dynamics and finite-time cross-diffusion between Brownian particles. The results unify convergence, fluctuation, and entanglement as consequences of a single feedback-driven stochastic principle.
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Materials Science · Cross-listed from cs.ET

Ovonic switches enable energy-efficient dendrite-like computing

Unhyeon Kang, Jaesang Lee, Seungmin Oh et al. (+9 more)

Over the last decade, dendrites within individual biological neurons, which were previously thought to generally perform information pooling and networking, have now been shown to express complex temporal dynamics, Boolean-like logic, arithmetic, signal discrimination, and edge detection for image and sound recognition. Mimicking this rich functional density could offer a powerful primitive for neuromorphic computing, which has sought to replace the aging digital computing paradigms using biological inspirations. Here, using electrically driven Ovonic threshold switching in Sb-Te-doped GeSe, we demonstrate a single two-terminal component capable of self-sustained dynamics and universal Boolean logic, in addition to XOR operations (which is traditionally thought to require a network of active components). We then employ logic-driven dynamics in a single component to detect and estimate the gradients of edges in images, a task that otherwise requires elaborate circuits. A network of Ovonic switches exhibits properties of a half adder and a full adder, in addition to discriminative logic accommodating inhibitory and excitatory signals. We show that this computational primitive is not only seemingly simpler, but also offers many orders of magnitude improved energy efficiency compared to prevailing digital solutions. As such, this work paves the path for potentially emulating dendrites for efficient post-digital neuromorphic computing.
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All authors Unhyeon Kang, Jaesang Lee, Seungmin Oh, Hanchan Song, Jongkil Park, Jaewook Kim, Seongsik Park, Hyun Jae Jang, Sangbum Kim, Su-in Yi, Suhas Kumar, Suyoun Lee

2512.23736 · 24 Dec · 17 pages, 5 figures, 1 table. Published in Nano Letters (2025). This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Nano Letters, copyright (c) American Chemical Society after peer review. To access the final edited and published work see https://pubs.acs.org/doi/full/10.1021/acs.nanolett.5c04348

Abstract PDF $CRCT ×1$NRN ×1

Materials Science

Toward reducing the formation temperature of diopside via wet-chemical synthesis routes using chloride precursors

N. Namvar, E. Salahinejad, A. Saberi et al. (+3 more)

Reducing the formation temperature of single-phase multioxides is one of the classic challenges in ceramic processing, including wet-chemical synthesis routes. Toward pursuing this aim for diopside (MgCaSi2O6), the merit of different sol-gel and coprecipitation processes using the related chloride precursors followed by calcination was compared from the viewpoints of crystallinity and homogeneity. In accordance to the results, the use of the sol-gel techniques, directed with/without an alkaline catalyst, gave rise to the unfavorable creation of multiphase and low-crystallinity structures. Regarding the coprecipitation methods, the one-step addition of a precipitant agent is accompanied by an indirect low-temperature formation of nano-diopside, while a direct crystallization into this phase was explored in the dropwise condition, albeit with a lower crystallinity. Thus, by employing a suitable synthesis processing, it is feasible to take control of a wide range of nanoparticulate diopside-based structures achieved after a low-temperature calcination.
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All authors N. Namvar, E. Salahinejad, A. Saberi, M.J. Baghjeghaz, L. Tayebi, D. Vashaee

Materials Science

Representations of the symmetry groups of infinite crystals

Bachir Bekka and Christian Brouder

We investigate the representations of the symmetry groups of infinite crystals. Crystal symmetries are usually described as the finite symmetry group of a finite crystal with periodic boundary conditions, for which the Brillouin zone is a finite set of points. However, to deal with the continuous crystal momentum $\mathbf{k}$ required to discuss the continuity, singularity or analyticity of band energies $\epsilon_n(\mathbf{k})$ and Bloch states $\psi_{\mathbf{k}}$, we need to consider infinite crystals. The symmetry groups of infinite crystals belong to the category of infinite non-compact groups, for which many standard tools of group theory break down. For example, character theory is no longer available for these groups and we use harmonic analysis to build the group algebra, the regular representation, the induction of irreducible representations of the crystallographic group from projective representations of the point groups and the decomposition of a representation into its irreducible parts. We deal with magnetic and non-magnetic groups in arbitrary dimensions. In the last part of the paper, we discuss Mackey's restriction of an induced representation to a subgroup, the tensor product of induced representations and the symmetric and antisymmetric squares of induced representations.
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Statistical Mechanics · Cross-listed from quant-ph

Algebraic Fusion in a (2+1)-dimensional Lattice Model with Generalized Symmetries

Chinmay Giridhar, Philipp Vojta, Zohar Nussinov et al. (+2 more)

The notion of quantum symmetry has recently been extended to include reduced-dimensional transformations and algebraic structures beyond groups. Such generalized symmetries lead to exotic phases of matter and excitations that defy Landau's original paradigm. Here, we develop an algebraic framework for systematically deriving the fusion rules of topological defects in higher-dimensional lattice systems with non-invertible generalized symmetries, and focus on a (2+1)-dimensional quantum Ising plaquette model as a concrete illustration. We show that bond-algebraic automorphisms, when combined with the so-called half-gauging procedure, reveal the structure of the non-invertible duality symmetry operators, which can be explicitly represented as a sequential quantum circuit. The resulting duality defects are constrained by the model's rigid higher symmetries (lower-dimensional subsystem symmetries), leading to restricted mobility. We establish the fusion algebra of these defects. Finally, in constructing the non-invertible duality transformation, we explicitly verify that it acts as a partial isometry on the physical Hilbert space, thereby satisfying a recent generalization of Wigner's theorem applicable to non-invertible symmetries.
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All authors Chinmay Giridhar, Philipp Vojta, Zohar Nussinov, Gerardo Ortiz, Andriy H. Nevidomskyy

Disordered Systems and Neural Networks · Cross-listed from quant-ph

Observation of disorder-induced superfluidity

Nicole Ticea, Elias Portoles, Eliott Rosenberg et al. (+299 more)

The emergence of states with long-range correlations in a disordered landscape is rare, as disorder typically suppresses the particle mobility required for long-range coherence. But when more than two energy levels are available per site, disorder can induce resonances that locally enhance mobility. Here we explore phases arising from the interplay between disorder, kinetic energy, and interactions on a superconducting processor with qutrit readout and control. Compressibility measurements distinguish an incompressible Mott insulator from surrounding compressible phases and reveal signatures of glassiness, reflected in non-ergodic behavior. Spatially-resolved two-point correlator measurements identify regions of the phase diagram with a non-vanishing condensate fraction. We also visualize the spectrum by measuring the dynamical structure factor. A linearly-dispersing phonon mode materializes in the superfluid, appearing even when disorder is introduced to the clean Mott insulator. Our results provide strong experimental evidence for disorder-induced superfluidity.
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All authors Nicole Ticea, Elias Portoles, Eliott Rosenberg, Alexander Schuckert, Aaron Szasz, Bryce Kobrin, Nicolas Pomata, Pranjal Praneel, Connie Miao, Shashwat Kumar, Ella Crane, Ilya Drozdov, Yuri Lensky, Sofia Gonzalez-Garcia, Thomas Kiely, Dmitry Abanin, Amira Abbas, Rajeev Acharya, Laleh Aghababaie Beni, Georg Aigeldinger, Ross Alcaraz, Sayra Alcaraz, Markus Ansmann, Frank Arute, Kunal Arya, Walt Askew, Nikita Astrakhantsev, Juan Atalaya, Ryan Babbush, Brian Ballard, Hector Bates, Andreas Bengtsson, Majid Bigdeli Karimi, Alexander Bilmes, Simon Bilodeau, Felix Borjans, Alexandre Bourassa, Jenna Bovaird, Dylan Bowers, Leon Brill, Peter Brooks, Michael Broughton, David A. Browne, Brett Buchea, Bob B. Buckley, Tim Burger, Brian Burkett, Jamal Busnaina, Nicholas Bushnell, Anthony Cabrera, Juan Campero, Hung-Shen Chang, Silas Chen, Zijun Chen, Ben Chiaro, Liang-Ying Chih, Agnetta Y. Cleland, Bryan Cochrane, Matt Cockrell, Josh Cogan, Paul Conner, Harold Cook, Rodrigo G. Cortiñas, William Courtney, Alexander L. Crook, Ben Curtin, Sayan Das, Martin Damyanov, Dripto M. Debroy, Stijn J. de Graaf, Laura De Lorenzo, Sean Demura, Lucia B. De Rose, Agustin Di Paolo, Paul Donohoe, Andrew Dunsworth, Valerie Ehimhen, Alec Eickbusch, Aviv Moshe Elbag, Lior Ella, Mahmoud Elzouka, David Enriquez, Catherine Erickson, Lara Faoro, Vinicius S. Ferreira, Marcos Flores, Leslie Flores Burgos, Sam Fontes, Ebrahim Forati, Jeremiah Ford, Brooks Foxen, Masaya Fukami, Alan Wing Lun Fung, Lenny Fuste, Suhas Ganjam, Gonzalo Garcia, Christopher Garrick, Robert Gasca, Helge Gehring, Robert Geiger, Élie Genois, William Giang, Dar Gilboa, James E. Goeders, Edward C. Gonzales, Raja Gosula, Alejandro Grajales Dau, Dietrich Graumann, Joel Grebel, Alex Greene, Jonathan A. Gross, Jose Guerrero, Tan Ha, Steve Habegger, Tanner Hadick, Ali Hadjikhani, Monica Hansen, Matthew P. Harrigan, Sean D. Harrington, Jeanne Hartshorn, Stephen Heslin, Paula Heu, Oscar Higgott, Reno Hiltermann, Jeremy Hilton, Hsin-Yuan Huang, Mike Hucka, Christopher Hudspeth, Ashley Huff, William J. Huggins, Evan Jeffrey, Shaun Jevons, Zhang Jiang, Xiaoxuan Jin, Cody Jones, Chaitali Joshi, Pavol Juhas, Andreas Kabel, Dvir Kafri, Hui Kang, Kiseo Kang, Amir H. Karamlou, Ryan Kaufman, Kostyantyn Kechedzhi, Julian Kelly, Tanuj Khattar, Mostafa Khezri, Seon Kim, Paul V. Klimov, Can M. Knaut, Alexander N. Korotkov, Fedor Kostritsa, John Mark Kreikebaum, Ryuho Kudo, Arun Kumar, Ben Kueffler, Vladislav D. Kurilovich, Vitali Kutsko, Nathan Lacroix, Tiano Lange-Dei, Brandon W. Langley, Pavel Laptev, Kim-Ming Lau, Emma Leavell, Loick Le Guevel, Justin Ledford, Joy Lee, Kenny Lee, Brian J. Lester, Wendy Leung, Matthew T. Lloyd, Lily L Li, Wing Yan Li, Ming Li, Alexander T. Lill, William P. Livingston, Aditya Locharla, Erik Lucero, Daniel Lundahl, Aaron Lunt, Sid Madhuk, Aniket Maiti, Ashley Maloney, Salvatore Mandrà, Leigh S. Martin, Orion Martin, Eric Mascot, Paul Masih Das, Dmitri Maslov, Melvin Mathews, Cameron Maxfield, Jarrod R. McClean, Matt McEwen, Seneca Meeks, Anthony Megrant, Kevin C. Miao, Reza Molavi, Sebastian Molina, Shirin Montazeri, Charles Neill, Michael Newman, Anthony Nguyen, Murray Nguyen, Chia-Hung Ni, Murphy Yuezhen Niu, Nicholas Noll, Logan Oas, William D. Oliver, Raymond Orosco, Kristoffer Ottosson, Alice Pagano, Sherman Peek, David Peterson, Alex Pizzuto, Rebecca Potter, Orion Pritchard, Michael Qian, Chris Quintana, Arpit Ranadive, Ganesh Ramachandran, Matthew J. Reagor, Rachel Resnick, David M. Rhodes, Daniel Riley, Gabrielle Roberts, Roberto Rodriguez, Emma Ropes, Eliott Rosenberg, Emma Rosenfeld, Dario Rosenstock, Elizabeth Rossi, David A. Rower, Robert Salazar, Kannan Sankaragomathi, Murat Can Sarihan, Kevin J. Satzinger, Sebastian Schroeder, Henry F. Schurkus, Aria Shahingohar, Michael J. Shearn, Aaron Shorter, Vladimir Shvarts, Volodymyr Sivak, Spencer Small, W. Clarke Smith, David A. Sobel, Barrett Spells, Sofia Springer, George Sterling, Jordan Suchard, Alexander Sztein, Madeline Taylor, Jothi Priyanka Thiruraman, Douglas Thor, Dogan Timucin, Eifu Tomita, Alfredo Torres, M. Mert Torunbalci, Hao Tran, Abeer Vaishnav, Justin Vargas, Sergey Vdovichev, Benjamin Villalonga, Catherine Vollgraff Heidweiller, Meghan Voorhees, Steven Waltman, Jonathan Waltz, Shannon X. Wang, Danni Wang, Brayden Ware, James D. Watson, Yonghua Wei, Travis Weidel, Theodore White, Kristi Wong, Bryan W. K. Woo, Christopher J. Wood, Maddy Woodson, Cheng Xing, Z. Jamie Yao, Ping Yeh, Bicheng Ying, Juhwan Yoo, Noureldin Yosri, Elliot Young, Grayson Young, Adam Zalcman, Ran Zhang, Yaxing Zhang, Ningfeng Zhu, Nicholas Zobrist, Zhenjie Zou, Sergio Boixo, Hartmut Neven, Vadim Smelyanskiy, Guifre Vidal, Erich Mueller, Trond Andersen, Lev Ioffe, Andre Petukhov, Mohammad Hafezi, Pedram Roushan

Soft Condensed Matter

Clogging of cohesive particles in a two-dimensional hopper

Johnathan Hoggarth, Pablo E. Illing, Eric R. Weeks et al. (+1 more)

We study clogging of cohesive particles in a 2D hopper with experiments and simulations. The system consists of buoyant, monodisperse oil droplets in an aqueous solution, where the droplet size, buoyant force, cohesion, and hopper opening are varied. Stronger cohesion enhances clogging, a trend confirmed in simulations. Balancing buoyant and cohesive forces defines a cohesive length scale that collapses the data onto a master curve. Thus, under strong cohesion, we find that clogging is governed not by particle diameter, but by the cohesive length scale.
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All authors Johnathan Hoggarth, Pablo E. Illing, Eric R. Weeks, Kari Dalnoki-Veress

Strongly Correlated Electrons

Disorder driven maximum in the magnetoresistance of spin polaron systems

Tanmoy Mondal and Pinaki Majumdar

Ferromagnetic polarons are self trapped states of an electron in a locally spin polarised environment. They occur close to the magnetic $T_c$ in low carrier density local moment magnets when the electron-spin coupling is comparable to the hopping scale. In non disordered systems the primary signatures are a modest non-monotonicity in the temperature dependent resistivity $\rho(T)$, and a magnetoresistance that can be $\sim 20-30 \%$ at $T_c$, at fields that, in energy units, are $\sim 0.01 k_BT_c$. We find that structural disorder, in the form of pinning centers, promotes polaron formation, hugely increases the resistivity peak at $T_c$, and can enhance the magnetoresistance to $\sim 80\%$. The change in magnetoresistance with disorder is, however, non-monotonic. Too much disorder just creates an Anderson insulator - with the resistivity unresponsive to the magnetisation. This paper establishes the optimum disorder for maximising the magnetoresistance, suggests the physical process behind the unusual disorder dependence, and provides a magnetoresistance map - in terms of coupling and disorder - that locates some of the existing magnetic semiconductors within this framework.
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Quantum Gases · Cross-listed from quant-ph

Hybrid digital-analog protocols for simulating quantum multi-body interactions

Or Katz, Alexander Schuckert, Tianyi Wang et al. (+3 more)

While quantum simulators promise to explore quantum many-body physics beyond classical computation, their capabilities are limited by the available native interactions in the hardware. On many platforms, accessible Hamiltonians are largely restricted to one- and two-body interactions, limiting access to multi-body Hamiltonians and to systems governed by simultaneous, non-commuting interaction terms that are central to condensed matter, quantum chemistry, and high-energy physics. We introduce and experimentally demonstrate a hybrid digital-analog protocol that overcomes these limitations by embedding analog evolution between shallow entangling-gate layers. This method produces effective Hamiltonians with simultaneous non-commuting three- and four-body interactions that are generated non-perturbatively and without Trotter error – capabilities not practically attainable on near-term hardware using purely digital or purely analog schemes. We implement our scheme on a trapped-ion quantum processor and use it to realize a topological spin chain exhibiting prethermal strong zero modes persisting at high temperature, as well as models featuring three- and four-body interactions. Our hardware-agnostic and scalable method opens new routes to realizing complex many-body physics across quantum platforms.
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All authors Or Katz, Alexander Schuckert, Tianyi Wang, Eleanor Crane, Alexey V. Gorshkov, Marko Cetina

Superconductivity

Thermodynamic Constraints on Perfect Equilibrium Superconducting Diodes

Pavan Hosur

Superconducting diodes promise dissipationless rectification, yet equilibrium platforms without engineered junctions typically exhibit modest efficiencies. We identify a general thermodynamic origin of this behavior that is largely independent of microscopic details. Denoting $\epsilon = |I_c^-/I_c^+|$, where $I_c^\pm$ are critical currents in opposite directions with $|I_c^+|>|I_c^-|$ by convention, we show that an exact perfect equilibrium diode ($\epsilon=0$) is forbidden by continuity of the free energy. Asymptotically perfect behavior $\epsilon\to0$ is possible within a global equilibrium description, but requires free-energy singularities to enable softening of the unfavorable current-carrying branch. We demonstrate this explicitly in an exactly solvable Ising superconductor model. For smooth single-branch superconductors, standard finite-order polynomial Landau theory yields finite lower bounds on $\epsilon$, while Josephson systems obey analogous bounds set by finite harmonic content of the current-phase relation. The high efficiencies often reported in Josephson platforms arise because such devices commonly operate under phase constraints, metastable switching, or external drive, thereby evading unconstrained equilibrium limits. Thus, our results provide a unified framework for interpreting diode efficiencies across superconducting platforms.
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Mesoscale and Nanoscale Physics

Orbitally Tuned Composite-Fermion Pairing Transitions in Bilayer Graphene

Ravi Kumar, Tomer Firon, André Haug et al. (+6 more)

The effective interaction between composite fermions, set entirely by the Coulomb potential and the underlying electronic Landau level orbitals, can stabilize exotic fractional quantum Hall states. In particular, half-filled Landau levels with different orbital character can host either metallic or paired phases of composite fermions. Here, we leverage experimental control over the orbital composition to realize a composite-fermion pairing transition in the first excited Landau level of bilayer graphene. Transport measurements at filling factors {\nu} = 9/2 and 11/2 reveal conductive states giving way to well-developed plateaus with increasing displacement fields. These states are insensitive to an in-plane magnetic field, indicating single-component ground states and thus pointing at non-Abelian orders. Our numerical study, based on displacement-field-dependent Landau-level wave functions, supports the orbital origin of the pairing transition and suggests Moore-Read or anti-Pfaffian ground states.
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All authors Ravi Kumar, Tomer Firon, André Haug, Misha Yutushui, Alon Ner Gaon, Kenji Watanabe, Takashi Taniguchi, David F. Mross, Yuval Ronen

Quantum Gases · Cross-listed from quant-ph

Bose polarons as relativistic Unruh-DeWitt detectors: Entanglement harvesting from Bose-Einstein condensates

T. Rick Perche, Francesco Gozzini and Markus K. Oberthaler

We show that a bound impurity in a Bose-Einstein condensate can be directly mapped to an Unruh-DeWitt detector interacting with a relativistic quantum field. We provide explicit experimental parameters for an implementation using ${}^{41}\text{K}$ impurities coupled to a ${}^{87}\text{Rb}$ condensate via finite-time Feshbach tuning. As an application, we study the extraction of vacuum entanglement from distant regions of the condensate and find viable parameters for the implementation of entanglement harvesting.
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Materials Science

Structure, biomineralization and biodegradation of Ca-Mg oxyfluorosilicates synthesized by inorganic salt coprecipitation

E. Salahinejad and M. Jafari Baghjeghaz

In this research, a novel group of Ca-Mg oxyfluorosilicates containing different levels of fluoride substituting for oxide was synthesized by an inorganic salt coprecipitation process followed by calcination/sintering. The effects of the incorporation of fluoride on the resultant structural characteristics, apatite-forming ability and biodegradability were evaluated by X-ray diffraction, transmission electron microscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, inductively coupled plasma spectroscopy and pH measurements. According to the results, the samples containing up to 2 mol% F present a single-phase structure of diopside (MgCaSi2O6) doped with F. It was also found that to meet the most biomineralization characteristic, the optimal value of fluoride in the homogeneous samples is 1 mol%. In this regard, on the one hand, the partial incorporation of fluoride into apatite (via forming fluorohydroxyapatite) and, on the other hand, the absence of fluorite (CaF2) as a consumer of Ca in the deposits are responsible for achieving the most apatite-forming ability circumstance controlled by an ion-exchange reaction mechanism. In conclusion, this study reflects the merit of the optimization of fluoride-doping into Ca-Mg silicates for development in biomedicine.
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Materials Science

Channel-last gate-all-around nanosheet oxide semiconductor transistors

Fabia F. Athena, Xiangjin Wu, Nathaniel S. Safron et al. (+18 more)

As we move beyond the era of transistor miniaturization, back-end-of-line-compatible transistors that can be stacked monolithically in the third dimension promise improved performance for low-power electronics. In advanced transistor architectures, such as gate-all-around nanosheets, the conventional channel-first process involves depositing dielectrics directly onto the channel. Atomic layer deposition of gate dielectrics on back-end-of-line compatible channel materials, such as amorphous oxide semiconductors, can induce defects or cause structural modifications that degrade electrical performance. While post-deposition annealing can partially repair this damage, it often degrades other device metrics. We report a novel channel-last concept that prevents such damage. Channel-last gate-all-around self-aligned transistors with amorphous oxide-semiconductor channels exhibit high on-state current ($>$ 1 mA/$\mu$m) and low subthreshold swing (minimum of 63 mV/dec) without the need for post-deposition processing. This approach offers a general, scalable pathway for transistors with atomic layer deposited channel materials, enabling the future of low-power three-dimensional electronics.
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All authors Fabia F. Athena, Xiangjin Wu, Nathaniel S. Safron, Amy Siobhan McKeown-Green, Mauro Dossena, Jack C. Evans, Jonathan Hartanto, Yukio Cho, Donglai Zhong, Tara Peña, Paweł Czaja, Parivash Moradifar, Paul C. McIntyre, Mathieu Luisier, Yi Cui, Jennifer A. Dionne, Greg Pitner, Iuliana P. Radu, Eric Pop, Alberto Salleo, H.-S. Philip Wong

Strongly Correlated Electrons

Topological Charge-2ne Superconductivity and Clustering Hierarchy

Zhi-Qiang Gao, Yan-Qi Wang, Hui Yang et al. (+1 more)

Charge-$2ne$ superconductors condense clusters of more than two electrons, extending superconductivity beyond Cooper pairing. They exhibit distinctive signatures including fractional flux quantization $h/(2ne)$ and are actively being explored in strongly correlated systems. We develop a general framework for constructing and characterizing topological charge-$2ne$ superconductors by combining wavefunction and field theory approaches. Generalizing the Read-Green wavefunction and Higgsing Read-Rezayi-type states yield two families that can support deconfined non-Abelian anyons and non-Abelian superconducting vortices. The first family also admits a construction from doping Jain states. Through Higgs theories, we find that the first and second families realize weak and intermediate clustering regimes, respectively, distinguished by the topology of vortices carrying flux greater than $h/(2ne)$, while strong clustering yields a charge-$2ne$ superconductor without intrinsic topological order. These reveal that higher-charge superconductivity supports a richer hierarchy of topological phases beyond the Read-Green weak-strong pairing dichotomy, with distinct internal clustering structures giving rise to different topological structures at fixed condensate charge.
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All authors Zhi-Qiang Gao, Yan-Qi Wang, Hui Yang, Congjun Wu

Statistical Mechanics

Universality of equilibration dynamics after quantum quenches

Vincenzo Alba, Sanam Azarnia, Gianluca Lagnese et al. (+1 more)

We investigate the distribution of the eigenvalues of the reduced density matrix (entanglement spectrum) after a global quantum quench. We show that in an appropriate scaling limit the lower part of the entanglement spectrum exhibits “universality”. In the scaling limit and at asymptotically long times the distribution of the entanglement spectrum depends on two parameters that can be determined from the Rényi entropies. We show that two typical scenarios occur. In the first one, the distribution of the entanglement spectrum levels is similar to the one describing the ground-state entanglement spectrum in Conformal Field Theories. In the second scenario, the lower levels of the entanglement spectrum are highly degenerate and their distribution is given by a series of Dirac deltas. We benchmark our analytical results in free-fermion chains, such as the transverse field Ising chain and the XX chain, in the rule 54 chain, and in Bethe ansatz solvable spin models.
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All authors Vincenzo Alba, Sanam Azarnia, Gianluca Lagnese, Federico Rottoli

Materials Science

Adhesion Energy of Phosphorene on Different Pristine and Oxidized Metallic Substrates

Matteo Vezzelli, Carsten Gachot and Maria Clelia Righi

Black phosphorus and its single-layer constituent, phosphorene, have emerged as promising two-dimensional materials with remarkable tribological properties. However, recent experimental investigations revealed that the their lubricating capabilities can change with the substrate. The present computational study employs density functional theory calculations to quantify the adhesion energy of both pristine and oxidized phosphorene monolayers on various metallic substrates (aluminum, copper, iron, and chromium) and their corresponding oxides ($\mathrm{Al_2O_3}$, $\mathrm{Cu_2O}$, $\mathrm{Fe_2O_3}$, and $\mathrm{Cr_2O_3}$), correlating these interfacial property with experimentally observed tribological performance. Results demonstrate that oxidized phosphorene presents higher adhesion to all substrates with respect to pristine phosphorene, attributed to favorable interactions between oxygen non-bonding states and substrate empty states. Adhesion is systematically more favorable on pristine metals than on their corresponding oxides, with chromium and iron showing particularly strong interactions due to partially filled 3d orbitals. This result is consistent with the coefficient of friction decrease observed in tribological experiments after scratching the iron substrate, thus removing the outermost oxide layer. Charge redistribution correlates with the adhesion and electronic structure analyses reveal system-dependent interfacial bonding characteristics, with some configurations inducing metallic character in phosphorene. These findings provide fundamental insights into substrate-dependent lubricating properties of black phosphorus, highlighting the key role of layer-substrate adhesion.
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Mesoscale and Nanoscale Physics

A Generalized Approach to Relaxation Time of Magnetic Nanoparticles With Interactions: From Superparamagnetism to Glassy Dynamics

Jean Claudio Cardoso Cerbino and Diego Muraca

A novel theoretical expression for the relaxation time of magnetic nanoparticles with dipolar interactions is derived from Kramers' theory, extending the Boltzmann-Gibbs framework to incorporate Tsallis statistics. The model provides a unified description of magnetic relaxation from weakly to strongly interacting regimes. It accounts for both the decrease and the increase of the relaxation time with increasing dipolar coupling, addressing a long-standing problem in nanoparticle magnetism that cannot be consistently described by classical phenomenological models. This result also offers an innovative interpretation of the cut-off condition inherent to the Tsallis distribution in terms of a cut-off temperature, T_cut-off, which naturally characterizes the onset of glassy freezing dynamics and provides an alternative interpretation of experimental relaxation data within a non-extensive statistical framework.
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Materials Science · Cross-listed from cs.LG

MiST: Understanding the Role of Mid-Stage Scientific Training in Developing Chemical Reasoning Models

Andres M Bran, Tong Xie, Shai Pranesh et al. (+9 more)

Large Language Models can develop reasoning capabilities through online fine-tuning with rule-based rewards. However, recent studies reveal a critical constraint: reinforcement learning succeeds only when the base model already assigns non-negligible probability to correct answers – a property we term 'latent solvability'. This work investigates the emergence of chemical reasoning capabilities and what these prerequisites mean for chemistry. We identify two necessary conditions for RL-based chemical reasoning: 1) Symbolic competence, and 2) Latent chemical knowledge. We propose mid-stage scientific training (MiST): a set of mid-stage training techniques to satisfy these, including data-mixing with SMILES/CIF-aware pre-processing, continued pre-training on 2.9B tokens, and supervised fine-tuning on 1B tokens. These steps raise the latent-solvability score on 3B and 7B models by up to 1.8x, and enable RL to lift top-1 accuracy from 10.9 to 63.9% on organic reaction naming, and from 40.6 to 67.4% on inorganic material generation. Similar results are observed for other challenging chemical tasks, while producing interpretable reasoning traces. Our results define clear prerequisites for chemical reasoning training and highlight the broader role of mid-stage training in unlocking reasoning capabilities.
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All authors Andres M Bran, Tong Xie, Shai Pranesh, Jeffrey Meng, Xuan Vu Nguyen, Jeremy Goumaz, David Ming Segura, Ruizhi Xu, Dongzhan Zhou, Wenjie Zhang, Bram Hoex, Philippe Schwaller

Materials Science

PhononBench:A Large-Scale Phonon-Based Benchmark for Dynamical Stability in Crystal Generation

Xiao-Qi Han, Ze-Feng Gao, Wen-Kao Li et al. (+2 more)

In recent years, generative artificial intelligence has made significant advances in the design of crystalline materials, giving rise to approaches based on graph neural networks, diffusion models, and large language models. Existing evaluations commonly follow the stability-uniqueness-novelty (S.U.N.) framework, where stability is primarily assessed using thermodynamic criteria, which do not fully capture the dynamical stability essential for a material's practical existence. Dynamical stability is a key determinant of whether a material can be synthesized and persist, with phonon spectrum calculations serving as the standard for its evaluation. However, the high computational cost of such calculations has prevented large-scale assessment of dynamical stability in generated crystals. In this work, we introduce PhononBench, the first large-scale benchmark for dynamical stability in AI-generated crystals. Leveraging the recently developed MatterSim interatomic potential, which achieves density-functional-theory (DFT)-level accuracy in phonon predictions across more than 10,000 materials, PhononBench enables efficient phonon calculations and dynamical-stability analysis for 133,838 crystal structures generated by 7 leading crystal generation models. PhononBench reveals a widespread limitation of current generative models: unless otherwise specified, all reported dynamical-stability metrics are evaluated at a phonon-frequency threshold of -0.1 THz, with the average dynamical-stability rate across all generated structures being only 32.15%, and the top-performing model, MatterGen, reaching just 45.05%.In addition, we identify 32,995 crystal structures that are phonon-stable across the entire Brillouin zone under a strict threshold of -0.001 THz. In addition, a web-based service is accessible at http://phononbench.cn/, enabling minute-level ultra-fast phonon predictions.
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All authors Xiao-Qi Han, Ze-Feng Gao, Wen-Kao Li, Peng-Jie Guo, Zhong-Yi Lu

Other Condensed Matter

Observation of High-Order Anisotropic Magnetoresistance in a Cubic Ferromagnet

Haoran Chen, Yue Chen, Yizi Feng et al. (+10 more)

High-order anisotropic magnetoresistance (AMR) is observed up to the 18th harmonic in cubic Fe(001) thin films, overturning the long-standing paradigm that only two- and four-fold terms are symmetry-allowed. Using angle-resolved transport and Fourier analysis, we show that six-fold and higher-order terms are intrinsic, tunable by temperature and thickness, and predicted by crystal symmetry. Microscopically, the two-fold sign reversal arises from a crossover between weak and strong scattering regimes, while high-order terms emerge from the interplay of anisotropic Fermi velocity and relaxation time. Our results establish high-order AMR as a symmetry-prescribed property of cubic ferromagnets, providing critical benchmarks for spin-orbit transport theory and enabling new angular-sensitive spintronic functionalities.
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All authors Haoran Chen, Yue Chen, Yizi Feng, Ruda Guo, Yuanfei Fan, Hongyue Xu, Tong Wu, Zhongxun Guo, Di Yue, Xiaofeng Jin, Yi Liu, Zhe Yuan, Yizheng Wu

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

3D cavity-based graphene superconducting quantum circuits in two-qubit architectures

Kuei-Lin Chiu, Avishma J. Lasrado, Cheng-Han Lo et al. (+4 more)

We construct a series of graphene-based superconducting quantum circuits and integrate them into 3D cavities. For a single-qubit device, we demonstrate flux-tunable qubit transition, with a measured $T_1$ $\approx$ 48 ns and a lower bound estimate of $T_2^\ast$ $\approx$ 17.63 ns. By coupling the device to cavities with different resonant frequencies, we access multiple qubit-cavity coupling regimes, enabling the observation of vacuum Rabi splitting and flux-dependent spectral linewidths. In a two-qubit device consisting of a SQUID and a single junction, power-dependent measurements reveal a two-stage dispersive shift. By flux-tuning the cavity frequency at different readout powers, we attribute the first shift to the fixed-qubit and the second to the SQUID-qubit, indicating successful coupling between the two circuits and a single cavity mode. Our study demonstrates the flexible coupling achievable between 2D-material-based superconducting circuits and 3D cavities, and paves the way toward constructing multi-qubit 3D transmon devices from 2D materials.
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All authors Kuei-Lin Chiu, Avishma J. Lasrado, Cheng-Han Lo, Yen-Chih Chen, Shih-Po Shih, Yen-Hsiang Lin, Chung-Ting Ke

Strongly Correlated Electrons

Quantum geometry in correlated electron phases: from flat band to dispersive band

Taisei Kitamura, Akito Daido and Youichi Yanase

Quantum geometry, describing the geometric properties of the Bloch wave function in momentum space, has recently been recognized as a fundamental concept in condensed matter physics. The flat-band system offers the paradigmatic platform where quantum geometry plays the essential role in correlated electron phases. However, systems that suffer from significant effects of quantum geometry are not limited to flat-band systems; dispersive-band systems also exhibit quantum condensed phases driven by quantum geometry. In this perspective, we provide a transparent account of quantum geometry and its role in correlated electron phases, throughout flat-band and dispersive-band systems.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.optics

Controlling photothermal forces and backaction in nano-optomechanical resonators through strain engineering

Menno H. Jansen, Cauê M. Kersul and Ewold Verhagen

In micro- and nanoscale optomechanical systems, radiation pressure interactions are often complemented or impeded by photothermal forces arising from thermal strain induced by optical heating. We show that the sign and magnitude of the photothermal force can be engineered through deterministic nanoscale structural design, by considering the overlap of temperature and modal strain profiles. We demonstrate this capability experimentally in a specific system: a nanobeam zipper cavity by changing the geometry of its supporting tethers. A single design parameter, corresponding to a nanoscale geometry change, controls the magnitude of the photothermal backaction and even its sign. These insights will allow engineering the combined photothermal and radiation pressure forces in nano-optomechanical systems, such that backaction-induced linewidth variations are deterministically minimized if needed, or maximized for applications that require cooling or amplification at specific laser detuning.
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Mesoscale and Nanoscale Physics

Coupled-wire construction of non-Abelian higher-order topological phases

Jiaxin Pan and Longwen Zhou

Non-Abelian topological charges (NATCs), characterized by their noncommutative algebra, offer a framework for describing multigap topological phases beyond conventional Abelian invariants. While higher-order topological phases (HOTPs) host boundary states at corners or hinges, their characterization has largely relied on Abelian invariants such as winding and Chern numbers. Here, we propose a coupled-wire scheme of constructing non-Abelian HOTPs and analyze a non-Abelian second-order topological insulator as its minimal model. The resulting Hamiltonian supports hybridized corner modes, protected by parity-time-reversal plus sublattice symmetries and described by a topological vector that unites a non-Abelian quaternion charge with an Abelian winding number. Corner states emerge only when both invariants are nontrivial, whereas weak topological edge states of non-Abelian origins arise when the quaternion charge is nontrivial, enriching the bulk-edge-corner correspondence. The system further exhibits both non-Abelian and Abelian topological phase transitions, providing a unified platform that bridges these two distinct topological classes. Our work extends the understanding of HOTPs into non-Abelian regimes and suggests feasible experimental realizations in synthetic quantum systems, such as photonic or acoustic metamaterials.
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Soft Condensed Matter

Multi-Tau Pulsed Illumination Differential Dynamic Microscopy with 80 $\mu$s Resolution

Emmanuel Schaub and Martinus H. V. Werts

Differential dynamic microscopy (DDM) is a digital video-microscopy technique for quantitative measurements of the microscale dynamics in soft condensed matter systems. Here, multi-tau pulsed illumination DDM (MTPI-DDM) is introduced as a method for significantly enhancing the time resolution of DDM. The technique employs simple, low-cost instrumentation comprising a single monochrome digital camera and a single pulsed LED. A timing sequence, following a geometric progression of time lags, is used to generate a "multi-tau" scheme, providing high sampling density at short timescales where dynamics are fastest. In the current implementation, a time resolution of 80 $\mu$s is achieved, limited by the dead time of the camera electronics. Validation of MTPI-DDM was performed by measuring the diffusion of 147 nm polystyrene nanoparticles in water. Compared to conventional continuous-wave (CW) DDM, the pulsed approach extends the range of the shortest measurable time lags by nearly two orders of magnitude and enhances DDM signal amplitudes by eliminating motion blur.
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Materials Science

Features of the Electronic and Magnetic Properties of Heusler Alloys in the States of a Half-Metallic Ferromagnet and a Spin-Gapless Semiconductor

V. V. Marchenkov, V. Yu. Irkhin and Yu. A. Perevozchikova

The review treats Heusler alloys that display distinctive functional properties, including shape-memory behavior and magnetocaloric effects. Particular emphasis is placed on Heusler systems in which half-metallic ferromagnetism and spin-gapless semiconductor state are realized. Although these compounds are crystallographically rather "ordinary", peculiarities of their electronic structure and magnetic state lead to unconventional kinetic and magnetic properties. Their magnetic and transport characteristics are highly sensitive to external stimuli, and changes in alloy composition or external parameters can induce transitions between the states considered. This tunability provides further opportunities for controlling the electronic and magnetic properties of Heusler alloys and for exploiting them in applications such as spintronics and micro- and nanoelectronics.
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Materials Science

Substrate Role in Polaron Formation on Single-layer Transition Metal Dihalides

Affan Safeer, Oktay Güleryüz, Guangyao Miao et al. (+3 more)

Single-layer transition metal dihalides grown on conducting substrates were shown to host stable polarons. Here, we investigate polarons in insulating single-layer MnBr$_2$ grown by molecular beam epitaxy on three different substrates, namely graphene on Ir(110), graphene on Ir(111), and Au(111). The number densities and species of polarons observed vary strongly as a function of the substrate. For MnBr$_2$ grown on Ir(110) the largest number of polaron species is observed, namely four, of which three show clear similarities with the species observed for CoCl$_2$ on graphite. Polarons in single-layer MnBr$_2$ are observed up to 300K. They can be created, converted, and moved by the STM tip when a tunneling current flows at a proper bias voltage. For graphene on Ir(110) as a substrate, mobile polarons in MnBr$_2$ are guided through the periodic potential imposed from the super-moiré resulting from the interaction of MnBr$_2$ with graphene and Ir(110). Our findings indicate that modeling of polarons in such single-layer insulators in contact with a conducting substrate requires to take the substrate explicitly into account.
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All authors Affan Safeer, Oktay Güleryüz, Guangyao Miao, Wouter Jolie, Thomas Michely, Jeison Fischer