Materials Science · Cross-listed from cs.LG
Geometry-free prediction of inertial lift forces in microfluidic devices using deep learning
Jesse Ward-Bond, Ali Mashadian, Timothy C. Y. Chan et al. (+1 more)
Inertial microfluidic devices (IMDs) offer low-cost, high-throughput alternative techniques for many traditional particle- (or
cell-) manipulation tasks, but simulating them requires being able to predict particle migration, and thus particle lift forces, under a variety of possible channel geometries. Recent work has demonstrated that machine learning models can be used to drastically speed up these numerical simulations, but doing so required training individual models for every unique channel cross-section type (e.g., rectangular, triangular) – shifting the burden from the simulation step to the training step. In this paper, we develop a novel approach for predicting particle lift forces that contains no explicit
geometric parameters. We train a neural network model using a new parameter set and show that while it performs comparably to existing models on channel geometries in the training set, it is able to generalize to unseen channel geometries far more effectively. We show that the lift force model developed herein can be easily transferred to particle tracing simulation software, where it is capable of predicting particle migration patterns consistent with the literature across a variety of channel designs.
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All authors Jesse Ward-Bond, Ali Mashadian, Timothy C. Y. Chan, Edmond W. K. Young
Strongly Correlated Electrons
Opto-criticality in Drude metals near the plasma frequency
Bikram Keshari Behera, Rhitabrata Bhattacharyya and Shyamal Biswas
Within a simple unified framework of classical electrodynamics that incorporates background bound charges and currents, we have analytically determined the attenuation constant, phase constant, and reflectivity of Drude metals across the full frequency spectrum ($0 < \omega < \infty$).Our result for reflectivity agrees well with existing experimental data for both
plasmas and seawater. Notably, for highly conductive Drude metals ($\omega_p \tau \gg 1$), the attenuation constant simplifies to $k_- \simeq \sqrt{\frac{\mu \epsilon}{2}} \sqrt{\omega_p^2 - \omega^2 + \vert{}\omega_p^2 - \omega^2\vert{}}$ across a broad high-frequency range spanning the
plasma frequency $\omega_p$. The branch-point singularity at $\omega=\omega_p$ in this relation reveals opto-critical behavior near $\omega=\omega_p$ in properties such as the attenuation constant, group velocity, and complex dielectric constant, for which we have determined the corresponding opto-critical exponents. Furthermore, we have incorporated
quantum corrections into these optical properties via the Drude-Sommerfeld model with Thomas-
Fermi screening.
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Statistical Mechanics
Statistical mechanics in continuous space with tensor network methods
Gunhee Park, Tomislav Begušić, Si-Jing Du et al. (+2 more)
Tensor network (TN) methods are well established for computing partition functions in statistical mechanics, though this use has traditionally been limited to
lattice models. We extend the scope of TN methodology to interacting particle systems in continuous space. Through a real-space discretization combined with a
cell-based coarse-graining scheme, we formulate an effective
lattice model that explicitly preserves spatial locality. The partition function of this model is represented as a TN, and the thermodynamic quantities are computed via boundary contraction. We apply this framework to the two-dimensional hard-disk problem and demonstrate the strengths of the TN formulation compared to existing Monte Carlo simulations.
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All authors Gunhee Park, Tomislav Begušić, Si-Jing Du, Johnnie Gray, Garnet Kin-Lic Chan
Disordered Systems and Neural Networks · Cross-listed from physics.chem-ph
Thermal conductivity of aligned polymers with kinks
Igor V. Parshin, Igor V. Rubtsov and Alexander L. Burin
Thermal conductivity of aligned
polymer molecules can be exceptionally high along the
alignment direction due to energy transport through strong covalent bonds. At the same time, it is highly sensitive to molecular conformation, varying by orders of magnitude as a result of gauche kinks. Here, we theoretically investigate
phonon transport in kinked
polymers by numerically evaluating thermal conductivity and interpreting the results in terms of
phonon scattering from randomly distributed kinks. For strongly aligned
polymers with restricted deviations from a linear backbone, we find that heat transport becomes superdiffusive at long lengths, with thermal conductivity scaling as $\kappa \propto L^{1/3}$. At shorter lengths, thermal conductivity exhibits non-monotonic behavior: it increases at very short scales due to ballistic transport of almost all
phonons, then decreases at intermediate lengths due to the Anderson localization of most
phonon modes. These results are consistent with experiments and molecular dynamics simulations, and they elucidate the microscopic mechanisms governing heat transport in
polymers.
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Mesoscale and Nanoscale Physics
Probing GHz Spin Dynamics Across Magnetic Phase Transitions in CrCl3 Nanoflakes Using Nitrogen-Vacancy Microscopy
Benjamin Hammons, Jitender Kumar, Sehrish Iqbal et al. (+11 more)
CrCl3, a layered van der Waals (vdW) magnet, exhibits in-plane
magnetic anisotropy and enhanced interlayer coupling upon stacking, making it an ideal platform to host exotic nanoscale
magnetic phenomena such as
magnon hydrodynamics and meron-like topological
spin defects. When interfaced with other vdW materials, its
antiferromagnetic-to-
ferromagnetic and
ferromagnetic-to-paramagnetic phase transitions and
magnetic anisotropy can be tuned by voltage, strain, and layer stacking. Understanding the
spin dynamics of CrCl3 at its
magnetic phase transitions is crucial to its applications in magnonics. Here, we investigate the
spin dynamics of CrCl3 nanoflakes using cryogenic diamond
quantum sensing microscopy, based on measuring optically detected
magnetic resonance, Rabi oscillations, and
spin-
lattice relaxation time (T1) of shallow nitrogen vacancy (NV) centers in diamond. In the
ferromagnetic regime, we observe a pronounced reduction in the NV
spin resonance contrast, a collapse of the Rabi oscillations, and a strong enhancement by two orders of magnitude of the relaxation rate G1 = 1/T1. These observations indicate intensified
spin fluctuations in the gigahertz range. Broadband
ferromagnetic resonance spectroscopy on CrCl3
crystals reveals resonance frequencies in the 4-15 GHz range together with a linewidth of ~24 mT, further supporting the NV measurements. A phenomenological model of
magnetic-noise-induced NV relaxation reproduces the temperature dependence of G1 by combining
antiferromagnetic,
ferromagnetic, and paramagnetic fluctuation channels, indicating that
magnetic noise is strongest in the
ferromagnetic regime and evolves markedly across the phase transition. These results are crucial for using CrCl3 in 2D magnonics and hybrid
quantum-
magnon systems.
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All authors Benjamin Hammons, Jitender Kumar, Sehrish Iqbal, Prem Bahadur Karki, Karishma Prasad, Tianlin Li, Aram Pirali, Ayodimeji E. Aregbesola, Rupak Timalsina, Xia Hong, Jian Wang, Kapildeb Ambal, Ilja Fescenko, Abdelghani Laraoui
Materials Science · Cross-listed from physics.flu-dyn
Effects of temperature-dependent material properties in coldwater Rayleigh-Bénard convection
Gustavo Estay, Daisuke Noto and Hugo N. Ulloa
Water exhibits an anomalous nonlinear density equation of state (EOS) as it approaches freezing, along with an increase in viscosity ($\mu$) and a decrease in thermal conductivity ($k$). Here we ask: how do these temperature-dependent material properties affect thermal convection in coldwater? We examine these effects within the canonical Rayleigh-Bénard convection (RBC) system, performing direct numerical simulations with coldwater between $0^{\circ}$C and the temperature of maximum density $3.98^{\circ}$C. To disentangle the effects of these properties, we consider two main cases: RBC with a quadratic EOS and constant $\mu$ and $k$; and RBC with a quadratic EOS and temperature-dependent $\mu(T)$ and $k(T)$. We show that the most significant consequence is a shift in the mean fluid temperature relative to `standard RBC'. The nonlinear EOS and the temperature-dependent $\mu$ and $k$ drive this shift in opposite directions, with the former dominating and producing a net decrease in the mean temperature. This decrease varies with the Rayleigh number $Ra$, reaching up to $0.08^{\circ}$C at $Ra=10^{8}$. Additionally, the onset of convection is affected, but the influence from the EOS and $\mu(T)$ and $k(T)$ compensate, resulting in a negligible net effect. Despite these changes, the Nusselt and the Reynolds numbers follow classical scalings in all cases. Our results establish how the anomalous material properties of coldwater affect local and global features of convection, evidencing the implications of model selection for studies of cryospheric water bodies.
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Soft Condensed Matter
Entropic Trapping of Hard Spheres in Spherical Confinement
Praveen K. Bommineni, Junwei Wang, Nicolas Vogel et al. (+1 more)
Monodisperse spherical colloidal particles confined within emulsion droplets can crystallize into icosahedral clusters. Experimentally it was observed that a few large colloidal particles added as defects preferentially migrate to the vertices of the icoshedral clusters. To understand this structure formation phenomenon, we simulate the confined self-assembly of hard spheres in the presence of a small number of larger particles. The results demonstrate that large spheres are significantly influenced by concentric shells of small spheres near the crystallization transition. Entropic forces drive the large spheres to the cluster surface, where they settle into free energy minima at the icosahedron vertices. Notably, the addition of twelve large spheres results in the formation of a perfect icosahedral frame. Free energy calculations via umbrella sampling are used to quantify this process and show that both the migration to the cluster surface and the trapping at the vertices with trapping strength of multiple $k_\text{B}T$ results from free energy minimization. Moreover, our study reveals that the crystallization pathway and dynamics of large spheres are consistent across different systems, suggesting robustness of entropic trapping.
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All authors Praveen K. Bommineni, Junwei Wang, Nicolas Vogel, Michael Engel
Strongly Correlated Electrons
Crystal-Field Symmetry Constraints in Layered Honeycomb ErBr$_3$
Biaoyan Hu, Mingyuan Hu, Franz Demmel et al. (+3 more)
Crystal-field
symmetry restricts the ground-state Kramers doublet of ErBr$_3$ to one of two classes. We show that the compressed octahedral environment selects the class with $\langle \psi_\pm | J^{\pm} | \psi_\mp \rangle = 0$, suppressing the lowest-order $J^{\pm}$-mediated exchange. Thermodynamic measurements reveal two zero-field anomalies at 0.375 and 0.200 K. Under an in-plane
magnetic field, the thermodynamic response separates into a phase boundary and a broader crossover line. Inelastic
neutron scattering measurements at 2 K reveal no well-defined low-energy dispersive
magnetic modes. These results connect the ground-state
symmetry with the field-dependent thermodynamic response of ErBr$_3$, providing a microscopic starting point for understanding its low-energy
magnetic behavior.
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All authors Biaoyan Hu, Mingyuan Hu, Franz Demmel, Andrey A. Podlesnyak, Jiaqing He, Liusuo Wu
Statistical Mechanics
On the Mathematics of Information-Thermodynamics
Dallin Fisher and Qi-Jun Hong
We present a validation of the asdf method, an information-theoretic framework for computing thermodynamic
entropy from molecular configurations. The method reformulates
entropy estimation as the Shannon
entropy of a residual mapping distribution defined between two decorrelated microstates. We demonstrate analytically that for the closed-form
Hamiltonians with known solutions, the classical ideal gas and the one-dimensional harmonic oscillator's
entropy obtained from the compressibility of the residual mapping object reproduces the exact thermodynamic
entropy. In each case, the conditional
entropy of the residual mapping object with respect to an uncorrelated microstate is shown to coincide with the ensemble
entropy derived from the canonical partition function. These results establish consistency between the asdf formalism and classical statistical mechanics for analytically solvable systems. We further discuss how the framework generalizes to interacting
Hamiltonians. The analysis supports the interpretation of thermodynamic
entropy as an information measure encoded geometrically in inter-microstate mappings and motivates application of the method to complex condensed phases.
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Materials Science
Visualizing Crystallization Dynamics and Transformation Pathways of Disordered Rocksalt Oxides During Thermally Activated Sol-Gel Synthesis
Diyi Cheng, Tim Kodalle, Anika T. Promi et al. (+7 more)
Sol-gel synthesis is a wet-chemical processing route for the fabrication of functional materials offering control over composition, morphology, and microstructure at relatively low processing temperatures compared to conventional solid-state synthesis methods. While the sol-gel process initiates with intermixed molecular precursors, the transformation pathways at the early nucleation stage are insufficiently understood. Here, the chemical and structural transformation of disordered rocksalt (DRX) Li1.2Mn0.4Ti0.4O2 (LMTO), a promising cathode material for lithium batteries, is studied by multiscale characterization tools. In situ heating transmission electron microscopy (TEM) using a
liquid cell visualizes and identifies crystallization pathways at nanoscale. While some regions follow a classical multi-step transition through thermodynamically stable intermediates, others exhibit a kinetic shortcut in which intermediate nanocrystals dissolve into a localized amorphous
matrix that directly precipitates the DRX structure. Macroscale FTIR corroborates the findings to be related to chemically distinct microenvironments in the gel precursor, with transition metal ions more strongly incorporated into the acetate-coordinated network than lithium. Although in situ heating TEM captures diverse local transformation pathways, in situ SXRD indicates that the macroscopic transformation proceeds predominantly through spinel LMTO and lithium titanite intermediates toward DRX-LMTO. The findings shed light on the spatiotemporal chemical and structural transformations in sol-gel derived DRX-LMTO materials, and call for fine tuning of such sol-gel chemistries to manipulate the crystallization pathways and achieve target material homogeneity more efficiently.
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All authors Diyi Cheng, Tim Kodalle, Anika T. Promi, Ansuman Halder, Raphael F. Moral, Madeline Grass, Venkata S. Avvaru, Haegyeom Kim, Carolin M. Sutter-Fella, Haimei Zheng
Strongly Correlated Electrons
Dielectric signatures of crystal-field and low-temperature correlated dynamics in NdMgAl11O19
Sonu Kumar, Gaël Bastien, Maxim Savinov et al. (+3 more)
We report dielectric spectroscopy of single-crystalline \ce{NdMgAl11O19}, a magnetoplumbite hexaaluminate in which localized \ce{Nd^{3+}} moments coexist with a polarizable \ce{AlO5} bipyramidal network. The real part of the permittivity, $\varepsilon'_{c}(T)$, measured along the crystallographic $c$ axis, increases as the temperature is lowered from 275~K to 30~K and is frequency-independent between 4~Hz and 50~kHz. At lower temperatures, a frequency-dependent decrease in permittivity is observed, followed by a further upturn below 2~K. The high-frequency $\varepsilon'_{c}(T)$ is described by a Barrett formula supplemented by an effective two-level contribution, yielding a robust gap of $\Delta = 25.85 \pm 0.32$~K consistent with the lowest \ce{Nd^{3+}}
crystal-electric-field (CEF) splitting. Below $\sim 30$~K, the dielectric response becomes strongly frequency and
magnetic-field dependent. Isothermal $\varepsilon_c'(H)$ measurements reveal a reproducible low-field crossover near $\mu_0H_c \simeq 0.85$~T, which we attribute to the competition between
antiferromagnetic correlations and Zeeman splitting of the ground-state Kramers doublet. \ce{NdMgAl11O19} thus provides a Kramers reference system in which dielectric signatures of the excited-state CEF
manifold can be distinguished from those of the field-tuned, correlation-dominated ground-state doublet sector in a centrosymmetric frustrated magnetoplumbite host
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All authors Sonu Kumar, Gaël Bastien, Maxim Savinov, Małgorzata Śliwińska-Bartkowiak, Ross H. Colman, Stanislav Kamba
Disordered Systems and Neural Networks
Theory of Anderson localization on the hyperbolic plane
Alexander Altland, Tobias Micklitz, Devasheesh Sharma et al. (+2 more)
The two-dimensional
hyperbolic plane, $\mathbb{H}^2$, is an unusual system in that dimensionality changes with scale: locally two-dimensional and planar at short distances, but effectively infinite-dimensional at large scales, it provides an interesting paradigm for the study of (
quantum) phase transitions, notably the disorder-driven Anderson transition. Generalizing previous work, which treated short and large distance scales separately, we develop a unified framework interpolating between the principles of low- and high-dimensional Anderson localization. As a main result, we derive a two-parameter flow in a plane spanned by scale-dependent
curvature (setting the system's effective dimensionality) and conductivity, with an extended critical line separating metallic and insulating phases.
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All authors Alexander Altland, Tobias Micklitz, Devasheesh Sharma, Maksimilian Usoltcev, Carolin Wille
Quantum Gases
Phase diagram of a dual-species Rydberg atom ladder
Lei-Yi-Nan Liu, Shi-Rong Peng, Ze-Yuan Huang et al. (+4 more)
Dual-species Rydberg atom arrays extend single-species platforms by introducing competing interaction scales and enhanced
quantum fluctuations, enabling phenomena beyond homogeneous settings. In this work, we study the ground-state phase diagram of a one-dimensional dual-species Rydberg atom ladder using large-scale density-
matrix renormalization group calculations. We identify disordered phases, multiple ordered phases with $\mathbb{Z}_2$, $\mathbb{Z}_3$, and $\mathbb{Z}_4$
symmetry, as well as floating phases characterized by incommensurate wave vectors and algebraically decaying correlations. Importantly, we observe a smooth crossover between distinct $\mathbb{Z}_2$-ordered regimes, reflecting a reorganization of low-energy degrees of freedom rather than a true phase transition, which is absent in single-species Rydberg arrays. We further uncover a multi-critical point at the boundary between the $\mathbb{Z}_2 \otimes \mathbb{Z}_2$ and $\mathbb{Z}_3 \otimes \mathbb{Z}_3$ ordered phases, where Ising,
chiral, and first-order transition lines intersect. Our results demonstrate that dual-species Rydberg atom arrays provide a unique platform for realizing crossover physics and multi-critical behavior inaccessible in single-species architectures.
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All authors Lei-Yi-Nan Liu, Shi-Rong Peng, Ze-Yuan Huang, Xing-Man Wei, Yun-Han Zou, Su Yi, Jian Cui
Strongly Correlated Electrons
Symmetry-Protected Topological Phases in the Triangular Majorana-Hubbard Ladder
Will Holdhusen, Alberto Nocera, Jian-Xin Zhu et al. (+1 more)
We uncover a family of
symmetry-protected topological phases in a model of interacting Majorana
fermions on triangular-
lattice ladders. Included among these phases is one in which
symmetry-protected topological order coexists with spontaneous
symmetry breaking associated with an adiabatically evolving set of
symmetries. Our results indicate a mechanism through which interactions among Majorana modes generate nontrivial
symmetry-fractionalized orders. These phases may be realized in arrays of
vortex-bound Majorana zero modes on the surface of topological
superconductors.
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All authors Will Holdhusen, Alberto Nocera, Jian-Xin Zhu, Armin Rahmani
Quantum Gases
Uncovering Exotic Paired States in the 2D Spin-Imbalanced Fermi Gas with Neural Wave Functions
Wan Tong Lou, Gino Cassella, Andres Perez Fadon et al. (+5 more)
We study the zero-temperature phase diagram of the 2D
spin-imbalanced
Fermi gas with short-ranged attractive interactions using the recently developed neural network variational Monte Carlo method with the AGPs FermiNet Ansatz. The Fulde-Ferrell-Larkin-Ovchinnikov phase is observed in the weakly interacting BCS limit and a polarised superfluid is seen in the strongly interacting BEC limit. When the interactions are strong, the minority-
spin momentum density is reduced almost to zero in the momentum-space region occupied by the unpaired majority-
spin electrons. When the interactions are very strong, phase separation occurs, with regions containing bosonic pairs and unpaired regions occupied by the remaining majority-
spin particles. In addition, we observe translational
symmetry breaking at intermediate interaction strengths, where the system forms an exotic
crystal of Cooper pairs in a
Fermi fluid of unpaired majority-
spin particles. We provide a possible explanation for the formation of the crystalline phase, explain the origins of the k-space momentum-density hole when the pairs are tightly bound, and discuss how our approach opens new directions for future work.
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All authors Wan Tong Lou, Gino Cassella, Andres Perez Fadon, Halvard Sutterud, David Pfau, James S. Spencer, Johannes Knolle, W.M.C. Foulkes
Strongly Correlated Electrons
Anomaly and symmetry-charge flow in mixed states
Ze-Min Huang and Sebastian Diehl
The $(1+1)$-dimensional
chiral anomaly is a paradigmatic exact result in
quantum field theory, traditionally formulated for zero-temperature pure states where it arises from spectral flow induced by external gauge fields and captures universal ground-state properties. In mixed states, however, the participation of many states and charge exchange with the environment invalidate this mechanism. Naive extensions yield model-dependent anomaly coefficients, calling its universality into question. Here, we resolve this problem for Abelian
symmetries by deriving the anomaly from an algebraic relation between the
symmetry and its flux-insertion operator. We obtain
symmetry-charge flow, a mixed-state generalization of spectral flow, in which an applied field redistributes statistical weight across
symmetry-resolved charge sectors. Fixed solely by
symmetry, the anomaly restores universality and applies to both pure and mixed states in fermionic and bosonic systems. We substantiate these results in tight-binding fermionic models with continuous
symmetry and in
spin models with discrete
symmetries.
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Strongly Correlated Electrons
Dynamical dimer structure factor of the triangular $S=1/2$ Heisenberg antiferromagnet
Markus Drescher, Laurens Vanderstraeten, Roderich Moessner et al. (+2 more)
The dynamical dimer structure factor is an observable probing
spin-singlet excitations of
quantum magnets distinct from those commonly studied by the
spin structure factor. We report the dimer response for the extended
spin-$1/2$
antiferromagnetic Heisenberg model on the triangular
lattice using large-scale GPU-accelerated
matrix-product-state simulations. We investigate the ordered phases with $120^\circ$ coplanar, collinear stripe, and tetrahedral
spin order, as well as candidate
quantum spin-
liquid (QSL) regimes, comprising an expected gapless $U(1)$ Dirac QSL and a
chiral QSL at finite
spin-scalar-chirality coupling. In the ordered phases, we find low-energy modes below the onset of the two-
magnon continuum illustrating avoided quasiparticle decay. Within the candidate gapless QSL, we observe absolute dispersion minima at momenta of half the Brillouin zone corners, $X\equiv K/2$, in agreement with field-theory predictions that singlet monopole excitations of the $U(1)$ Dirac
spin liquid become gapless at these points. Thus, the high-resolution dynamical dimer response provides support for a $U(1)$ Dirac QSL with singlet monopole excitations.
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All authors Markus Drescher, Laurens Vanderstraeten, Roderich Moessner, Frank Pollmann, Johannes Knolle
Mesoscale and Nanoscale Physics
Dispersion of Anyon Bloch Bands
Kishore Iyer, Andreas Feuerpfeil, Valentin Crépel et al. (+2 more)
Fractional Chern
insulators (FCIs) are zero
magnetic field analogs of fractional
quantum Hall states. While the electrons forming an FCI are not subject to an external
magnetic field, their anyonic excitations experience a
magnetic field with finite-flux due to a many-body Berry phase, whose
lattice periodicity generically induces some dispersion. From Laughlin wavefunctions at filling 1/m, we analytically construct single-anyon Bloch states in an ideal band, providing a basis to efficiently compute the dispersion. The anyon spectrum exhibits an $m$-fold degeneracy in the reduced
magnetic Brillouin zone (BZ), which originates from the topological degeneracy of the FCI. From our wavefunctions, we derive the m^2-fold degeneracy seen in previous works, showing it to be a splicing of anyon momenta into the electronic BZ. Finally, we find that the anyon dispersion bandwidth is controlled by
quantum geometry non-uniformity, growing linearly at weak modulation and saturating at strong modulation. Remarkably, higher harmonics of the
quantum geometry alone strongly suppress the dispersion, which we attribute to emergent
magnetic translation
symmetries. When combined with the first harmonic, a positive (negative) second harmonic drives the system toward a second- (first-) harmonic-dominated regime, thereby reducing (enhancing) the bandwidth. Our results offer an analytically controlled method for evaluating anyon spectra in ideal band FCI, shedding light on how non-uniform
quantum geometry and emergent
symmetries shape the dispersion of anyons.
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All authors Kishore Iyer, Andreas Feuerpfeil, Valentin Crépel, Nicolas Regnault, Christophe Mora
Mesoscale and Nanoscale Physics
Absence of Quasi-Majorana False Positives in Full-Shell Hybrid Nanowires
Carlos Payá, César Robles, Pablo San-Jose et al. (+1 more)
Tunneling spectroscopy cannot be used as an unambiguous detection tool for Majorana zero modes (MZMs) in conventional partial-shell nanowires. The presence of smooth confinement at the end of the hybrid wire (among other sources of disorder) can create exponentially pinned zero-energy states, called quasi-MZMs, that mimic all local signatures of MZMs but lack topological protection. We find that this ambiguity in MZM detection does not occur in full-shell hybrid nanowires, an alternative nanowire design where a superconducting shell fully surrounds the
semiconductor core. Acting as a synthetic
vortex, a full-shell hybrid nanowire hosts Caroli-de Gennes-Matricon state analogs. In the presence of smooth confinement, these states create a topologically trivial skin at the wire's end that prevents the local probe from detecting quasi-MZMs. In this way, the same mechanism that creates MZM impostors makes them invisible in tunneling spectroscopy, avoiding false positives produced by smooth disorder.
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All authors Carlos Payá, César Robles, Pablo San-Jose, Elsa Prada
Statistical Mechanics · Cross-listed from quant-ph
Randomised measurements of a disorder-induced entanglement transition in a neutral atom quantum processor
Apollonas S. Matsoukas-Roubeas, Oscar Scholin, Lucas Sá et al. (+5 more)
The development and spread of
entanglement in complex
quantum systems is central to exploring many-body phenomena out of
equilibrium. Measuring
entanglement dynamics can shed light on information scrambling and thermalisation, namely on transitions from many-body
quantum chaos to localisation in disordered, interacting systems. In
quantum computing systems,
entanglement entropy and other nonlinear functions of the density
matrix have been recently measured, in particular by using the randomised measurement toolbox. However, it is difficult to implement the required arbitrary
unitary rotations on specific subsystems without universal local control. Here we devise and demonstrate the measurement of
entanglement entropy in a programmable analogue
quantum simulator using a randomised measurement protocol that leverages local energy tuning together with a global field to bypass the need for local gate control. We implement this on a commercially available neutral-atom
quantum simulator, QuEra's Aquila, and use it to show how programmable disorder in the local
Hamiltonian parameters leads to a transition from chaotic to localised
entanglement dynamics. Given current decoherence times, we clearly resolve disorder-specific, time-dependent
entanglement spreading in small systems. Our work extends the utility of programmable analogue
quantum simulators, and opens further opportunities for wider randomised measurement toolboxes in a range of other analogue systems.
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All authors Apollonas S. Matsoukas-Roubeas, Oscar Scholin, Lucas Sá, Arinjoy De, Majd Hamdan, Alexei Bylinskii, Andrew J. Daley, Dorian A. Gangloff
Strongly Correlated Electrons
Universal Topological Power Transfer with Arbitrarily Large Chern Number in Driven Quantum Spin Chains
Anshuman Tripathi, Mircea Trif and Thore Posske
Topological frequency converters exploit a quantized transfer of power between two driving fields in a
quantum system, a phenomenon topologically protected by the Chern number of the associated fiber bundle. While realizations with few-
spin systems have theoretically demonstrated this effect, the conversion factors have typically been restricted to small integer values. Here, we investigate an interacting $XXZ$ Heisenberg
spin-$1/2$ chain driven adiabatically by two
magnetic drives with incommensurate frequencies. The Chern number, determined by the degeneracy points enclosed by the adiabatic trajectory, increases systematically with the chain length and can be tuned through the exchange anisotropy, providing direct control of the topological pumping strength. We reveal a universal dependency of the anisotropy and
magnetic field strength for odd and even chain lengths of the
quantum critical points. This provides a mechanism for a topological frequency converter with an arbitrarily large, quantized conversion ratio in interacting
quantum spin chains. The mechanism remains the same for arbitrary coupling regions of the drives.
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Strongly Correlated Electrons
Magnetic phases of the anisotropic triangular Hubbard model from the ghost-Gutzwiller approximation in the rotating spin-frame
Azin Kazemi-Moridani, Samuele Giuli, Tsung-Han Lee et al. (+4 more)
We investigate the
magnetic phase diagram of the half-filled Hubbard model on the anisotropic triangular
lattice using the Gutzwiller approximation (GA) and its ghost generalization (ghost-GA). By combining a rotating
spin-frame formulation with high-resolution momentum grids, we determine
magnetic ground states through direct total-energy minimization over the ordering wavevector. We
benchmark standard GA and ghost-GA against dynamical mean-field theory (DMFT) and dual-
fermion results. We show that GA already captures the qualitative structure of the phase diagram, but systematically overestimates the stability of
magnetic order due to the absence of dynamical fluctuations. We find that introducing a small number of auxiliary ”ghost” orbitals is sufficient to recover most dynamical effects and significantly improves quantitative agreement with DMFT. Exploring the full Brillouin zone, we obtain a phase diagram comprising paramagnetic and various
magnetic phases. In contrast to ladder dual-
fermion susceptibility-based predictions, we find that the one-dimensional
antiferromagnetic phase is never stabilized, despite being the leading instability in certain regimes. Our results establish ghost-GA as an efficient and systematically improvable framework for studying magnetism in frustrated systems, capable of achieving near-DMFT accuracy at a fraction of the computational cost. They also highlight that standard GA performs qualitatively well for capturing the general phase diagram, enabling the investigation of incommensurate
magnetic orders in more complex systems.
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All authors Azin Kazemi-Moridani, Samuele Giuli, Tsung-Han Lee, A.-M. S. Tremblay, Michel Côté, Nicola Lanatà, Olivier Gingras