Statistical Mechanics
A Fuzzy Sphere Journey in Critical Phenomena
Yin-Chen He and W. Zhu
This review discusses the recently proposed fuzzy sphere regularization for studying $2+1$D critical phenomena, particularly three-dimensional (3D) conformal field theory (CFT). The fuzzy sphere scheme not only offers remarkable efficiency in extracting extensive CFT data at low computational cost but also reveals unexpected connections among 3D CFT (critical phenomena), noncommutative geometry, and the
quantum Hall effect. We introduce the fundamental ideas of fuzzy sphere regularization, emphasizing its role in demonstrating the state-operator correspondence of 3D CFTs on the $S^2 \times \mathbb{R}$ geometry. Additionally, we review key developments in this approach across various directions and outline potential future applications.
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Superconductivity
Ising superconductivity and anomalous metallic states in a bulk crystal with artificial unidirectional stacking layers
Xiangqi Liu, Chen Xu, Haonan Wang et al. (+17 more)
The two-dimensional (2D) limit in macroscopic bulk
crystals provides a powerful platform for exploring exotic
quantum phases. Here, we report the synthesis of a Sr0.75ClNbS2
superconductor that achieves unidirectional, parallel AA stacking-a configuration never before realized in a bulk
crystal. Unlike conventional intercalation, which merely expands the interlayer spacing, our approach employs a planar Sr-Cl network to enforce a complete stacking reorganization, driving all NbS2 layers from the native antiparallel AB stacking into a unidirectional, parallel AA arrangement. This stacking switch globally breaks inversion
symmetry, transforming centrosymmetric 2H-NbS2 into a noncentrosymmetric bulk
crystal with D3h point group
symmetry. Crucially, this structural design reproduces, in three dimensions, the electronic environment of an isolated monolayer, thereby preventing cancellation of the local Ising fields. As a result, strong Ising
spin-orbit coupling and
spin-split bands persist throughout the bulk. Transport measurements reveal extreme superconducting anisotropy ({\gamma} ~ 77), an in-plane upper critical field (~ 10.65 T) that far exceeds the Pauli paramagnetic limit, and clean-limit superconductivity indicative of high crystalline quality. Moreover, magnetotransport uncovers a novel
magnetic-field-induced anomalous metallic state characterized by finite dissipation yet a vanishing
Hall response. Direct band-structure measurements corroborate the layer-decoupled, quasi-2D electronic nature of the system. This work establishes stacking-geometry engineering as a powerful strategy to artificially enforce a globally noncentrosymmetric, quasi-2D superconducting state in bulk
crystals, paving the way for designing
quantum materials with tunable crystalline
symmetry and electronic band
topology.
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All authors Xiangqi Liu, Chen Xu, Haonan Wang, Runfeng Zhang, Ziyi Zhu, Zhengyang Li, Lianbing Wen, Ze Yan, Fanbo Shen, Jiawei Luo, Zhengtai Liu, Xia Wang, Leiming Chen, Ke Qu, Jianping Sun, Jinguang Cheng, Shiwei Wu, Zhenzhong Yang, Dawei Shen, Yanfeng Guo
Materials Science
On the limits of the energetic coupling between field dislocation mechanics and phase field crystal
Aymane Graini, Jorge Viñals and Manas V. Upadhyay
This paper investigates the energetic coupling between Field Dislocation Mechanics (FDM) and the Phase Field
Crystal (PFC) model proposed in Phys. Rev. B 102, 064109, 2020. While FDM correctly solves the initial boundary value problem of a continuum body with dislocation fields, PFC captures the underlying crystallographic structure. The coupling, which penalizes the $L^2$ distance between elastic distortion from FDM and configurational distortion from PFC in the $L^2$ sense, had been proposed to reconcile dislocation mechanics with crystallography in a single continuum framework. Variational analysis reveals that the coupling term acts as a divergence-driven forcing in the phase-field
evolution that matches only the compatible (curl-free) parts of the distortion fields. Consequently, its contributions are insensitive to the incompatible (divergence-free) elastic distortion carrying all the information on dislocation
topology. Furthermore, the nature of the configurational distortion causes mechanical boundary conditions to be transmitted diffusively from FDM to PFC rather than elastically. Numerical simulations demonstrate that this coupling cannot prevent the unnatural core spreading in FDM. Finally, it is shown that even in the most general case, an energetic coupling suffers from the same drawbacks, which limits its ability to integrate dislocation mechanics with crystallography.
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Statistical Mechanics
Brownian ratchets and pumps universally simulate many-body active dynamics
Charles Stahl, Ethan Lake and Vedika Khemani
Active systems can exhibit a broad range of phenomena forbidden in
equilibrium. Their dynamics are often specified by abstract local update rules, and it is generally unclear when the same behavior can arise from physically natural driving. Here we show that two simple driving mechanisms can universally simulate any local active dynamics in
spin systems. The first is the familiar setting of a time-periodic
Hamiltonian coupled to a cold bath, which we call a "many-body Brownian pump." As a second mechanism, we promote the Brownian ratchet, traditionally a mechanism for transport, to a "many-body Brownian ratchet": a static
Hamiltonian coupled to a hot bath and a cold bath, where the resulting steady heat current can be harnessed not only to drive transport but also to generate local active dynamics. Using probabilistic cellular automata as an explicit model, we prove that for any continuous-time (or discrete-time) local active dynamics, there is always a many-body Brownian ratchet (or pump) that approximates the dynamics, up to noise that can be made arbitrarily weak by tuning energy scales and other parameters. As a concrete demonstration, we construct a simple
ferromagnetic Ising ratchet on a
bilayer lattice. When the two layers are coupled to baths at different temperatures, this model serves as a robust classical
memory even under a
symmetry-breaking field, something impossible in
equilibrium. More broadly, our work shows that ratchets can use steady heat currents to autonomously generate and stabilize novel collective behavior, realizing a new static setting for nonequilibrium many-body dynamics.
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Quantum Gases · Cross-listed from quant-ph
Polynomial equivalence of the global transverse-field Ising model and the gate model of quantum computation
Matthias Werner
The transverse-field Ising model has attracted a lot of
attention in recent years, especially in the
quantum simulation and
quantum computation literature. This interest is driven by many platforms for analog
quantum computation, which implement the transverse-field Ising model for solving optimization problems, such as
quantum annealing. However, it has remained an open question whether the Ising model with a global transverse field is equivalent to the gate model of
quantum computation. Here we answer this question affirmatively for the case of a non-monotonic time-dependent transverse field. Building on a recent result by Cesa and Pichler on global control of Rydberg atoms, we provide a construction that allows simulating arbitrary
quantum circuits using the Ising model with global transverse field with
polynomial overhead in time,
qubit number, and energy scale. Although the
polynomial overheads we establish here are large relative to what is feasible on real-world
quantum hardware, our result motivates the development of more sophisticated methods for simulating
quantum circuits using the Ising model with a global transverse field. Additionally, under the assumption that
quantum computing is strictly more powerful than classical computing, our result serves as a no-go
theorem for efficient classical simulation of the transverse-field Ising model with a time-dependent global transverse field. Therefore, our finding is relevant for multiple communities, from analog
quantum simulation and
quantum optimization on various platforms to complexity and control theory.
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Mesoscale and Nanoscale Physics
Confinement in a magnetically induced WSe$_2$ quantum dots
Rachid El Aitouni, Mohammed El Azar, Clarence Cortes et al. (+2 more)
Monolayer tungsten diselenide (WSe$_2$) has become a suitable platform for
quantum transport and spintronics and valleytronics applications because it possesses an intrinsic band gap and strong
spin-orbit coupling and
spin-valley coupling features. The electrostatic confinement of Dirac
fermions proves challenging in
graphene because of Klein tunneling, yet WSe$_2$ provides an environment that supports both carrier localization and the development of confined
quantum states. In this work, we theoretically investigate the confinement of massive Dirac
fermions in a WSe$_2$
quantum dot generated by a localized
magnetic field. Using the effective Dirac
Hamiltonian in the presence of a
magnetic flux, we derive the exact wave functions and scattering coefficients by employing Kummer's confluent hypergeometric functions together with Bessel and Hankel functions. Our results show that the localized
magnetic field provides an efficient mechanism to suppress Klein tunneling and promote the formation of stable quasibound states. We systematically examine the scattering efficiency and carrier density distributions as functions of the incident energy,
magnetic field strength, and
quantum dot radius. We find that low-energy carriers are strongly confined by the
magnetic barrier, while the interplay between
magnetic localization and
geometric confinement gives rise to sharp and tunable resonance peaks. These results provide valuable insight into the control of
spin-valley transport in transition metal dichalcogenide nanostructures and establish a theoretical basis for the development of
quantum confinement devices and
quantum information technologies.
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All authors Rachid El Aitouni, Mohammed El Azar, Clarence Cortes, David Laroze, Ahmed Jellal
Materials Science · Cross-listed from cs.AI
Optimal Resource Utilization for Autonomous Laboratory Orchestrators
Austin McDannald, Julia Tisaranni and Howie Joress
In autonomous laboratories, AI
agents suggest the next batch of experiments to do. However, planning and executing those tasks taking full advantage of the available resources is a completely different question. This can be challenging when dealing with real-world hardware constraints, especially so when there are multiple instruments with different capacities and throughputs. Here we demonstrate a 2-step method to address resource utilization for our autonomous platform for metal-organic framework synthesis. First, we use constraint programming to find optimal schedules. This finds schedules that minimizes the total time while still satisfying the limitations and capacities of the hardware. Secondly, we use a system of status dependencies for each task, which allows for the robust execution of the optimal schedules.
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Materials Science
Observation of Flat Bands in Type-II Weyl Semimetal TaRhTe$_{4}$
Harry Rankin, Tyler J. Slade, Benjamin Schrunk et al. (+7 more)
Flat bands have been theoretically predicted for decades but have only recently been realized in
quantum materials such as magic-angle twisted
bilayer graphene, kagome and Lieb
lattices, and rare-earth metal compounds. To date, only twisted layered materials have enabled tuning of flat-band energies near the electronic chemical potential, thereby influencing transport and thermodynamic properties. Here, we report the presence of flat bands near the chemical potential in bulk TaRhTe$_{4}$, a noncentrosymmetric van-der Waals type-II Weyl semimetal. Flat bands are rarely observed in Weyl semimetals, particularly in nonmagnetic bulk systems, and the observed flat bands were not predicted by density functional theory calculations. TaRhTe$_{4}$ therefore provides a platform in which nontrivial
topology coexists with flat bands near the
Fermi level, as evidenced by our angle-resolved photoemission spectroscopy measurements.
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All authors Harry Rankin, Tyler J. Slade, Benjamin Schrunk, Yevhen Kushnirenko, Andrew Eaton, K. U. R. R. S. Rathnayaka, Maxwell Doyle, Lin-Lin Wang, Paul C. Canfield, Adam Kaminski
Materials Science
Electric-field effects on defect migration energetics in GaN
Farshid Reza, Hamdy Arkoub, Alexander S. Hauck et al. (+2 more)
A predictive understanding of defect transport in GaN under operating electric fields is critical for assessing device reliability in high-power and radiation environments. In this work, a ReaxFF reactive force field for GaN is developed using a density-functional-theory training set that includes structural, thermodynamic, and defect properties. The force field yields various properties such as
lattice parameters, cohesive energies, and defect formation and migration energies in close agreement with prior first-principles and experimental results. Under externally applied electric fields, we find that migration barriers can be strongly modulated, with changes that depend on defect type and field orientation. Notably, the electric fields do not simply linearly bias defect motion in GaN, but can anisotropically modify migration barriers through charge-
lattice coupling, leading to nonlinear transport behavior. The response arises from field-induced partial charge redistribution and local
lattice distortion. These results demonstrate that electric fields can complexly modify the defect migration landscape, providing new insight into defect transport in GaN under high-field conditions.
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All authors Farshid Reza, Hamdy Arkoub, Alexander S. Hauck, Adri C.T. van Duin, Miaomiao Jin
Materials Science
Topological Hall effect due to electron-skyrmion scattering
Arijit Mandal, Hareram Swain, B. R. K. Nanda et al. (+1 more)
Electron scattering from
chiral spin textures such as skyrmions is fundamental to the understanding of transport in more complex systems, including skyrmion
crystals. Most of the previous studies have focused on the weak-coupling regime, where the exchange interaction is small compared with the electron energy. Real materials, however, often lie in the strong-coupling regime, which exhibits qualitatively different behavior. Using the Lippmann-Schwinger equation and Green's function formalism, valid for all coupling strengths, we uncover several new features in the scattering cross section, including Ramsauer-Townsend minima, pronounced intermediate-coupling resonances, and Landau-level resonances for skyrmions with larger winding numbers. These features strongly influence the topological and
spin Hall conductivities, which depend sensitively on the incident electron energy. Our work provides important insights into the
Hall transport in collective
chiral spin textures such as the skyrmion
crystal.
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All authors Arijit Mandal, Hareram Swain, B. R. K. Nanda, S. Satpathy
Strongly Correlated Electrons
Strange Luttinger liquids in a cavity-embedded one-dimensional electronic chain
Danh-Phuong Nguyen, Christophe Mora and Cristiano Ciuti
We study a one-dimensional electronic chain coupled to a homogeneous quantized
vacuum field and electron-electron interactions. In the absence of the latter, we derive a low-energy effective description in the presence of light-matter coupling, which we identify as a strange Luttinger
liquid. Although it retains a formal resemblance to conventional Luttinger
liquid theory, the coupling to the
quantum field qualitatively modifies the low-energy sector and breaks the standard velocity relation underlying Luttinger universality. For finite electron-electron interactions, we recover a phase diagram featuring several phases as a function of interaction strength and hopping amplitude, including a phase hosting Majorana-like zero modes. Using exact diagonalization, we compute observables that characterize the phase boundaries and show that the cavity field significantly shifts them. We also study the fate of Majorana-like states under the influence of the cavity field, highlighting their modification by light-matter coupling. Finally, we investigate whether the strange Luttinger
liquid description identified in the noninteracting regime continues to hold when electron-electron interactions are introduced.
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Materials Science
Diamond Diode for Extreme Venus Environments
Harshad Surdi, Gabriel Munro-Ludders, Mohamadali Malakoutian et al. (+9 more)
A diamond Schottky PIN diode (SPIND) with the highest reported current density to date of ~116 kA/cm2 is demonstrated carrying a total current of ~1.3 A through a 50 micron wide pseudo-vertical diode structure. The diamond SPIND also provides a maximum power handling capacity of 1.85 MW/cm2 and a low specific on-resistance Ron,S of 0.05 mOhm-cm2 at a forward bias of ~16 V. The diamond
SPIN diode also shows excellent rectification characteristics with a current on-off ratio of ~6e12. An analytical model including thermionic emission and space charge limited current is presented together with Silvaco ATLAS TCAD simulations, to accurately reproduce the experimental J-V characteristics using multiple single trap levels and other physical models emulating a real device. Theoretical analysis from the analytical models in conjunction with ATLAS simulations shows that further improvement in the device turn on voltage and Ron,S can be achieved by reducing the defect density and contact resistance in order to approach the ultimate performance in the Mott-Gurney space charge limited current regime
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All authors Harshad Surdi, Gabriel Munro-Ludders, Mohamadali Malakoutian, Srabanti Chowdhury, Savannah Eisner, Mohamed Fadil Isamotu, Mengyang Yuan, Stephen Goodnick, Franz Koeck, James Lyons, Trevor Thornton, Robert Nemanich
Strongly Correlated Electrons
Exact dimer ground states of long-range spin chains and ladders
Jędrzej Wardyn and Miłosz Panfil
Interacting
spin chains and ladders are known to support a plethora of
quantum phases with complex ground-state phase diagrams. In this work, we study a large family of such models and determine precise, explicit conditions under which an exact dimer state is guaranteed to be the ground state. These general conditions are validated for various generalizations of the Majumdar-Ghosh model using exact diagonalization. Our results provide exact reference points in the phase diagrams of a wide class of
spin chains and ladders, including those with anisotropic and arbitrary-range interactions.
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Statistical Mechanics
Universal Short-Imaginary-Time Quantum Critical Dynamics Near Boundaries
Yu-Rong Shu, Yuan-Biao Li and Shuai Yin
While imaginary-time
evolution has long served as a standard paradigm for ground-state preparation in numerical simulations and
quantum devices, its intrinsic dynamical properties has been largely overlooked. Here, we investigate the short-imaginary-time critical dynamics in
quantum systems with boundaries. A universal scaling theory is developed and verified in the two-dimensional
quantum Ising model, uncovering rich dynamic critical behaviors dictated by boundary universality classes. For ordered initial states, the boundary order parameter $M_s$ decays with imaginary time $\tau$ as $M_s \propto \tau^{-\beta_1/\nu z}$, where $\beta_1$ denotes the boundary order parameter exponent, and $\nu$ and $z$ correspond to the correlation length exponent and the dynamic exponent, respectively. For disordered initial states, the autocorrelation of the boundary order parameter is governed by a novel critical exponent $\theta_1$, which is closely related to the critical initial slip behavior of $M_s$ characterized by the corresponding exponent $\theta_1'$. In contrast to its positive bulk counterpart, the boundary initial-slip exponent $\theta_1'$ is negative for the ordinary transition while remaining positive for the special transition. Although the static universality classes of $d$-dimensional
quantum phase transitions generally coincide with those of $(d+1)$-dimensional classical phase transitions, we show that $\theta_1$ does not follow this conventional
quantum-classical mapping. We further discuss the implications of our results for more exotic forms of boundary criticality. Our findings provide new physical insights into boundary critical dynamics and offer a novel route for probing exotic boundary critical behaviors in
quantum many-body systems.
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Materials Science · Cross-listed from math-ph
Scattering, Trapping and Cloaking-Type Effects of Plane Waves by Point Scatterers in Strain Gradient Elasticity
E. Alevras, Th. Zisis and P. A. Gourgiotis
Wave scattering by localized constraints in microstructured solids is strongly influenced by the interplay of material length scales, dispersion and geometry. This work investigates plane-strain scattering of time-harmonic P and SV waves by clusters of rigid point constraints embedded in an infinite strain gradient elastic medium. A closed-form dynamic Green's tensor is derived for the plane-strain problem. Unlike the classical elastodynamic Green's tensor, the strain gradient Green's tensor remains bounded at the source, enabling point constraints to be introduced directly through superposition of fundamental solutions. The multiple-scattering problem is reduced to a finite-dimensional algebraic system for the pin reaction amplitudes. A frequency-domain procedure is developed to identify resonance-like amplification and trapping. Candidate resonant frequencies are associated with local minima of the Green
matrix determinant, while higher-order
curvature criteria distinguish trapping-dominated resonances from non-localized scattering responses. The results show that the response is governed primarily by the ratio of the microinertial and energetic strain gradient lengths. In the anomalous dispersion regime, sharp resonances produce strong displacement localization, including perimeter-localized trapping modes in dense circular arrays. In the normal dispersion regime, these resonances are strongly attenuated and the pins behave as weak scatterers, producing a cloaking-type response in which the incident field is only weakly perturbed. The influence of Poisson's ratio, incidence angle and compound pin configurations is also examined, demonstrating how intrinsic material lengths and
geometric arrangement can be used to tune scattering, trapping and wave-screening mechanisms in microstructured elastic media.
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Strongly Correlated Electrons
Chiral enhancement of two-magnon bound states in an $S=1/2$ triangular-lattice magnet
László Rudner and Karlo Penc
We study one- and two-
magnon excitations above the fully polarized state of the
spin-$1/2$ triangular-
lattice $J_1$-$J_2$-$J_3$ Heisenberg model with a uniform scalar-chirality interaction. In the Heisenberg model, we identify two special
manifolds of one-
magnon minima by rewriting the dispersion in complete-square form. The chirality term cancels exactly in the one-
magnon sector, leaving the dispersion and instability field unchanged, but survives in the two-
magnon sector as an oriented interaction between neighboring
magnons. Using
symmetry-adapted
lattice harmonics, we show that scalar chirality splits two-
magnon states of opposite relative-motion chirality and selectively enhances the binding of one of them. It can strengthen an existing bound state, change the
symmetry of the lowest
magnon pair, or induce binding where none occurs without chirality. Exact diagonalization further shows that two-
magnon pairing can also occur at finite total momentum. Our results identify scalar chirality as a microscopic mechanism for enhancing two-
magnon pairing without modifying the one-
magnon spectrum.
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Mesoscale and Nanoscale Physics
Bandwidth-Limited Critical Currents in Electrically Tunable Moiré Bands
Riccardo Bertini, Xueqiao Wang, Sergey Slizovskiy et al. (+16 more)
Moiré superlattices host narrow minibands whose bandwidth governs correlated and topological phases. Here, we demonstrate that the bandwidth also sets the critical current for the onset of out-of-
equilibrium transport. In
bilayer graphene aligned to hexagonal boron nitride, we explore the high-current transport regime as we continuously flatten the valence miniband using an out-of-plane displacement field. We observe a significant reduction in the critical current, which is captured by a minimal analytical model and corresponds to the calculated narrowing of the miniband. Moreover, by comparing distinct moiré platforms, we show that the scaling between critical current and bandwidth is a universal feature of
graphene superlattices. Our results reveal a direct link between miniband dispersion and high-current transport, and establish this regime as a fast and accessible electrical probe of bandwidth
evolution.
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All authors Riccardo Bertini, Xueqiao Wang, Sergey Slizovskiy, Zhiren Zheng, Julien Barrier, Chiara Pizzo, Robin Smeyers, Krystian Nowakowski, Hitesh Agarwal, Alvaro Moreno, Bert Jorissen, Kenji Watanabe, Takashi Taniguchi, Milorad V. Milošević, Lucian Covaci, Vladimir Fal'ko, Pablo Jarillo-Herrero, Roshan Krishna Kumar, Frank H. L. Koppens
Superconductivity
Breathing mode inducing dynamical pairing in Kagome materials
Debmalya Chakraborty, Anushree Datta and Jorge Cayao
The breathing mode in Kagome materials is a structural modulation that breaks inversion
symmetry and has been shown to be a crucial source for intriguing phases in the normal state. In this work, we carry out a full classification of superconducting
symmetries in kagome
superconductors and demonstrate the emergence of odd-frequency dynamical Cooper pairs entirely driven by the breathing mode. We then show that odd-frequency
spin-singlet Cooper pairs can be realized by controlling the breathing mode in kagome
lattices with conventional
spin-singlet $s$-wave superconductivity. Since odd-frequency pairing is intrinsically nonlocal in time, our results put forward the breathing mode for designing dynamical Cooper pairs in kagome materials.
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Strongly Correlated Electrons
Exact interlayer triplet-pairing eigenstates in the extended Hubbard model
F. X. Liu and Z. Song
$\eta$-pairing
symmetry generalizes the pairing mechanisms in superconductivity but is broken in the presence of interlayer interactions. In this work, we extend this approach to triplet pairs. We propose interlayer triplet-pairing operators for the multi-layer extended Hubbard model. We find that a set of exact condensate-pair eigenstates can be constructed, which exhibit off-diagonal long-range order. In contrast to the $\eta$-pairing mechanism, this originates from restricted spectrum generating
algebra and is only available for
bilayer and trilayer systems in the presence of interlayer Hubbard interactions. Nevertheless, the system also retains the original on-site $\eta$-pairing
symmetry in the absence of interlayer interactions. Consequently, both singlet and triplet pairs coexist in the eigenstates of the multi-layer Hubbard model. We employ quench dynamics to demonstrate the results through numerical simulations. Our findings open avenues for the study of exact condensate-pair states in strongly correlated systems.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Quantum-Informed Portfolio Selection: An End-to-End Pipeline Validated on Trapped-Ion Hardware with Real Market Data
Romina Yalovetzky, Martin J. A. Schuetz, Zichang He et al. (+11 more)
Portfolio diversification - a cornerstone of modern investment management - can be formulated as a Maximum Independent Set (MIS) problem on asset correlation graphs. Solving this problem at scale is computationally challenging, motivating the exploration of
quantum algorithms for practical financial optimization. We propose an end-to-end pipeline leveraging qReduMIS, a recursive hybrid
quantum-classical
algorithm. Rather than using
quantum optimization to directly produce a final solution, qReduMIS leverages independent set measurements from the
Quantum Approximate Optimization
Algorithm (QAOA) to identify frozen nodes - vertices likely to belong to optimal solutions - thereby guiding and unblocking subsequent (provably optimal) classical reductions on the remaining graph. We
benchmark qReduMIS on real financial data from four major
market indices with up to 225 assets, executing experiments on Quantinuum's 98-
qubit trapped-ion Helios system, with QAOA
circuits acting on kernels of up to 78
qubits and 1016 two-
qubit gates. While standalone QAOA fails to find the optimal solution for two of the largest indices (S&P 100 and Nikkei 225), qReduMIS achieves success probabilities of $0.40$ and $0.95$, respectively, with average approximation ratios $\geq 0.96$ across all four indices. We perform a systematic
benchmark on the Quantinuum H2-1 noisy emulator over 73 asset correlation graphs of varying size showing that, for $p=2$ QAOA layers, the optimal time-to-solution scaling exponent of qReduMIS is $3.2$ times smaller than that of standalone QAOA.
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All authors Romina Yalovetzky, Martin J. A. Schuetz, Zichang He, Jiayu Shen, Yue Sun, Rudy Raymond, Shauna Sahay, Kishore Perla, Ruben S. Andrist, Grant Salton, Helmut G. Katzgraber, Roger Bongiovanni, Niraj Kumar, Rob Otter
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Susceptibility-kinetic uncertainty relations for quantum systems
Didrik Palmqvist, Ludovico Tesser and Janine Splettstoesser
Kinetic uncertainty relations bound current precision of
stochastic processes by dynamical activity. The extension of these bounds to
quantum systems has been impeded by coherence, strong system-reservoir coupling, and the subtlety of defining dynamical activity in the
quantum regime. Here, we introduce a partial dynamical activity through the
quantum Fisher information associated with the rescaling of the system-reservoir coupling and show that it bounds current precision via a universal susceptibility-kinetic uncertainty relation. The general validity of this relation for any open
quantum system is guaranteed by the natural contribution of a susceptibility term, which is experimentally accessible by tuning the system-reservoir coupling strength. We show how the partial dynamical activity encompasses previous definitions of activity in the weak-coupling Markovian limit and that it provides an information-
geometric interpretation of correlator-based activities. We illustrate the tight constraint on precision that our bound provides with the example of steady-state transport through a double
quantum dot, where
quantum effects invalidate previously developed kinetic uncertainty relations. We expect our bound to provide a powerful tool for optimizing precision in arbitrary
quantum systems.
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Soft Condensed Matter
Diffusiophoretic transport of colloids and emulsions in complex environments
Amir A. Pahlavan
Chemical gradients are ubiquitous in porous and crowded environments, including soils, filters, fabrics, tissues, hydrogels, biofilms and living
cells. They arise from displacement fronts, dissolution and precipitation, ion exchange, metabolism, root exudation, evaporation, gas dissolution, freeze–thaw cycles and externally imposed chemical treatments. These gradients can drive colloids, macromolecules and emulsion droplets by diffusiophoresis, while simultaneously driving diffusioosmotic flows along confining surfaces. Classical models of colloid transport in porous media emphasize hydrodynamic dispersion, surface interactions, straining, deposition, detachment and filtration. This chapter places diffusiophoresis within that broader transport framework and reviews how porous media generate, stretch, disperse and sustain the solute gradients that drive phoretic motion. We first discuss sources of chemical gradients and the distinction between spreading and mixing, then summarize classical colloid transport, the minimal physicochemical model for diffusiophoresis and diffusioosmosis, and the experimental platforms used to study these effects. Particular emphasis is placed on recent results showing that diffuse solute fronts can enhance phoretic removal from dead-end pores by prolonging the duration of forcing, and that cross-streamline migration within flowing pathways can change macroscopic breakthrough and dispersion by orders of magnitude. We close by discussing emulsion droplets, multiphase flows, confined and living media, and open problems, including the transition from algebraic mixing in two-dimensional micromodels to chaotic mixing in three-dimensional porous media.
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Materials Science
Effect of radially heterogeneous band gap collapse on formation of swift heavy ion tracks in Al2O3
Roman Voronkov, Danil Zainutdinov, Nikita Medvedev et al. (+1 more)
We estimate the effects of radial heterogeneity in the collapse of the electronic band gap on the damage in Al2O3 after impact of a swift heavy ion decelerated in the electronic stopping regime. The Monte Carlo code TREKIS describes the initial excitation of the electronic and ionic systems following the ion passage, while the density functional theory based molecular dynamics traces changes in the band structure in the ion track. This combination of methods enables us to compute the profile of energy transferred to the
lattice by the time of relaxation of the electronic excitation, accounting for the induced spatial inhomogeneity of the band structure around the ion trajectory. We demonstrate that impact of a 700 MeV Bi ion induces a transient metal-
semiconductor heterojunction in Al2O3: the metallization (the band gap collapse) occurs within a radius of about 2 nm from the ion trajectory. The band gap shrinks at distances of about 3-5 nm, while it remains almost unaffected at radii larger than 5 nm. Using this data, we estimate the atomic heating depending on the degree of band gap reduction at different radii from the ion trajectory. This approach refines the damage modeling, producing more pronounced discontinuous damage patterns along the ion path for all crystallographic directions compared to the model that assumes all the energy accumulated in the electron-hole ensemble is delivered to the atoms.
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All authors Roman Voronkov, Danil Zainutdinov, Nikita Medvedev, Alexander E. Volkov
Statistical Mechanics
Phase diagram of a double-occupancy cell model of a fluid with Curie-Weiss interaction
R. V. Romanik, O. A. Dobush, M. P. Kozlovskii et al. (+2 more)
A double-occupancy
cell model of a fluid with Curie-Weiss interaction is studied. First, we show that the model is isomorphic to the Blume-Capel model on a complete graph through a simple transformation from
spin to occupancy variables. We then investigate its phase behavior within the grand-canonical ensemble using a combination of analytical and numerical methods. Despite its simplicity, the model exhibits a remarkably rich thermodynamic behavior depending on the ratio between the local repulsive and global attractive interactions. We identify the regimes characterized by a single critical point, two distinct critical points, tricritical behavior, and triple-point formation. For sufficiently strong repulsion, the system possesses three fluid phases of different densities, leading to both gas-
liquid and
liquid-
liquid coexistence. The locations of the critical, tricritical, and triple points are determined, and the corresponding phase diagrams are constructed. These results demonstrate that the competition between double-occupancy repulsion and long-range attraction is sufficient to generate a complex phase behavior in a minimal multiple-occupancy
lattice-gas-like model.
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All authors R. V. Romanik, O. A. Dobush, M. P. Kozlovskii, I. V. Pylyuk, M. A. Shpot
Materials Science
Complex crystal structure prediction using ML-enhanced multi-minima iterative genetic algorithm
Ling Tang, Weiyi Xia, Tyler J. Slade et al. (+2 more)
Current machine learning (ML) approaches for materials discovery rely heavily on known structural databases, limiting their ability to identify entirely novel structure types. In this work, we develop a multi-minima iterative genetic
algorithm (MMIGA) that integrates an artificial-neural-network machine learning (ANN-ML) interatomic potential with an iterative, metadynamics-inspired penalty scheme. We demonstrate the robustness of this method on a complex ternary La-Co-Pb system, characterized by Co-Pb immiscibility and an intricate energy landscape. The ML-enhanced MMIGA successfully predicts the ground-state Pbam structure of the recently synthesized La4Co4Pb antagonistic-pair-phase, a novel structure missed by previous database-reliant ML predictions, while also identifying multiple metastable competing phases. Additionally, we challenged the MMIGA method to predict the structure of La5CoPb2 antagonistic-pair-phase, a new compound discovered during earlier attempts to synthesize the predicted phase La3CoPb. With only knowledge of the composition, our MMIGA approach successfully predicts the orthorhombic structure of La5CoPb2, producing an exact match with the structure independently determined by x-ray diffraction. By efficiently mapping both global minimum and relevant competing metastable states, this approach provides critical theoretical insights into phase selection for novel
quantum and
magnetic materials.
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All authors Ling Tang, Weiyi Xia, Tyler J. Slade, Paul C. Canfield, Cai-Zhuang Wang
Materials Science
Geometry-Driven Magnetoelectric Coupling in Two-Dimensional Compensated Ferrimagnets
Peibo Xu, Yixuan Che, Haifeng Lv et al. (+2 more)
The magnetoelectric coupling in compensated magnets enables stray-field-free manipulation of
spin-splitting, holding great promise for spintronics, but inherently hindered by the
symmetry mismatch between spatial-inversion-broken ferroelectricity and time-reversal-broken
spin states. Here, based on a
symmetry-decoupled analysis of magnetoelectric coupling in compensated magnets, we establish a geometry-driven
spin-ferroelectric coupling mechanism in
bilayer breathing kagome
lattices. Within this
geometric framework interlocking the out-of-plane electric polarization with cooperative intralayer structural distortions, we demonstrate that polarization switching drives a deterministic reversal of the global
spin splitting. First-principles calculations on a prototype
bilayer Nb3Cl8 successfully validate this mechanism, demonstrating the switching of
spin-splitting states through an energetically feasible, asynchronous layer-by-layer transition pathway. Our proposed coupling originates from
lattice geometry and structural
symmetry, establishing a unique route toward switchable
spin splitting in compensated ferrimagnets.
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All authors Peibo Xu, Yixuan Che, Haifeng Lv, Xiaojun Wu, Jinlong Yang
Mesoscale and Nanoscale Physics
Exceptional points in dissipative coupling polaron-polaritons
A. J. Vega-Carmona, D. A. Mendoza, A. Camacho-Guardian et al. (+1 more)
Understanding how strong correlations and dissipation combine to shape collective
quantum excitations is a central challenge in many-body physics. We investigate the effect of dissipative light-matter coupling on strongly interacting
exciton-polaritons in the presence of a biexciton resonance, which gives rise to polaron-polariton quasiparticles. We show that the interplay between many-body correlations and non-Hermitian coupling generates anomalous dispersion relations and exceptional points in the polaron-polariton spectrum. The location and coexistence of exceptional points are controlled by the dissipative coupling and the relative decay rates of the excitonic and photonic constituents, allowing them to emerge across different polaron-polariton branches. These results identify dissipative polaron-polaritons as a versatile platform for exploring non-Hermitian many-body physics with tunable light-matter quasiparticles.
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All authors A. J. Vega-Carmona, D. A. Mendoza, A. Camacho-Guardian, M. A. Bastarrachea-Magnani
Mesoscale and Nanoscale Physics
Magnon-polaron mediated spin Seebeck effect in altermagnets
Ilia Moghayer, Ritesh Das and Yaroslav M. Blanter
Altermagnets, distinguished by compensated antiparallel
spins yet nondegenerate
magnon spectra, bridge the gap between ferromagnets and antiferromagnets. Although several probes such as anisotropic transport and spectroscopic measurements have been proposed to identify altermagnetic order, experimentally accessible transport signatures remain highly desirable. Here, we show that in altermagnets subject to an external
magnetic field, the
spin Seebeck effect exhibits pronounced directional anisotropy. Specifically, the
spin Seebeck coefficient differs significantly along in-plane directions, and this anisotropy increases with field strength. Magnetoelastic interactions further produce resonant peaks whose positions with respect to an applied
magnetic field reflect the intrinsic
magnon band anisotropy, and provide localized features that enhance the distinguishability of the altermagnetic response. The peaks provide a robust experimental signature of altermagnetic order. Our findings serve as signatures of altermagnetic order while laying the groundwork for their application in spintronic devices.
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Soft Condensed Matter
Single Chain Expulsion from Diblock Copolymer Micelles with Dense Corona
Shuang Yuan and Jiajia Zhou
We use self-consistent field theory to investigate the free energy landscape for single-chain expulsion from a diblock copolymer micelle with a dense corona. Using the distance from the micelle center-of-mass to the hydrophilic-hydrophobic junction of the chain as the reaction coordinate, we compute the free energy landscape for chain exchange. Our results show that the expulsion free energy barrier scales linearly with both the hydrophobic block length and the solvent selectivity, consistent with recent experiments. To accurately resolve chain conformation, we introduce a second reaction coordinate: the distance between the junction and the free end of the hydrophobic block, and construct a two-dimensional free energy surface. Using the string method to identify the minimum energy path, we find that all pathways converge to a nearly degenerate reaction channel, irrespective of the initial path. Within this channel, the end-to-end distance of the hydrophobic block exhibits a broad distribution, yet the corresponding expulsion barriers remain nearly indistinguishable. Together, these findings establish a continuum-level theoretical foundation for understanding the hyperstretching mechanism and the transition state ensemble in micellar chain exchange.
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Strongly Correlated Electrons
Tensor network solvers for ultra-large tight-binding Hamiltonians: algorithms and applications
Tiago V. C. Antão, Anouar Moustaj, Yitao Sun et al. (+1 more)
Understanding
quantum materials at meso and even macroscopic scales requires tight-binding calculations on system sizes where explicit
matrix representations become prohibitively costly. This represents a major bottleneck to rationalize phenomena in moiré and super-moiré
heterostructures and quasicrystals. Here, we present a unified tensor-network methodology to solve tight-binding problems at exceptionally large scales, by mapping a system of $N = 2^L$ sites onto a many-body problem of $L$ pseudospin sites, which is subsequently solved with tensor network
algorithms. For
Hamiltonians with compressible real-space structure, the tensor network bond dimension remains modest, typically of order a few tens, independent of $N$. Tensor network representations of arbitrary hopping functions including long-range, spatially modulated, and twisted-layer couplings are built with quantics tensor cross interpolation, and all physical observables are evaluated entirely with tensor network
algebra without explicit
matrix storage or diagonalization. We demonstrate applications to spectral functions, momentum-space spectra via the tensor-network
quantum Fourier transform, real-space topological invariants, real-time dynamics, correlation induced
symmetry breaking with self-consistent mean-field calculations, non-Hermitian phenomena, and excitonic many-body physics. Our methodology enables routinely solving systems with billions of sites, by leveraging the tensor network compressibility of real-space structures, and establishing a flexible framework to study
quantum matter at ultra-large length scales. The methodology is implemented in the open-source Julia package TensorBinding.
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All authors Tiago V. C. Antão, Anouar Moustaj, Yitao Sun, Jose L. Lado