Materials Science · Cross-listed from physics.optics
Propagation Maps, Maradona Exceptional Points, and Pele Singularities in Anisotropic, Tellegen, Chiral, Moving-Medium, Omega and Other Isotropy-Broken Materials
Maxim Durach
Anisotropic, Tellegen,
chiral, moving-medium-type, omega, gyrotropic,
hyperbolic, and multi-
hyperbolic materials form an important class of isotropy-broken photonic media in which wave propagation can no longer be characterized by the Fresnel wave surface alone. Here we show that Fresnel wave surfaces can be converted into propagation maps that organize positive- and negative-phase-velocity propagation together with attenuation and amplification. In Hermitian media, the boundary between forward and backward propagation forms the Michelangelo silhouette separatrix. This separatrix is also a continuous locus of Maradona exceptional points, where the index-of-refraction operator becomes defective even though the material medium remains Hermitian. In non-Hermitian media, the attenuation-amplification boundary forms the Caravaggio chiaroscuro separatrix. The associated Pele singularities occur where the handedness remains continuous while the gain-loss character changes sign. Their physical importance is revealed by the momentum-resolved density of states: at these points, the Lorentzian linewidth of the non-Hermitian momentum-resolved density of states (DOS) collapses, producing sharp DOS peaks whose sign reverses across the separatrix. Thus, Pele singularities are threshold-like gain-loss singularities of the Fresnel wave-surface propagation map, generated by non-Hermitian linewidth collapse. The result is a compact
geometric language for describing how handedness, degeneracy, loss, gain, and momentum-resolved DOS are organized in isotropy-broken electromagnetic materials.
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Soft Condensed Matter
A Design Framework for Compositional Hierarchical Mechanical Metamaterials via a Qualitative Unit-Cell Library
Shammo Dutta, Girish Krishnan and Sree Kalyan Patiballa
Hierarchically designed mechanical metamaterials involve nested levels of structural organization, mimicking natural structures (such as bones, wood, and bird feathers) to create advanced functional materials. Compositional hierarchy, a specific type of hierarchical strategy that involves the methodical assembly of discrete building blocks, offers unique advantages in engineering design due to its modular nature. This involves proper selection and spatial arrangements of distinct microstructures, as a result of which the desired macro-scale mechanical behavior can be achieved. Towards the design of such compositional hierarchical metamaterials, this paper presents a two-step design framework. First, material optimization of the design domain is performed using a parameterized elasticity
matrix to obtain optimal conceptual designs. Second, building-block microstructure geometries are selected from a qualitative library and subjected to shape-size refinement to satisfy the desired kinematic or stiffness requirements. To construct the qualitative library, a novel parametrization scheme is initially introduced, which categorizes the planar orthotropic elasticity
matrix into four distinct classes. Utilizing a kinetostatic load flow visualization technique, the candidate microstructure geometries are then populated within these four classes. The framework is validated for the design of a cantilever beam with a specified lateral stiffness requirement and the design of planar sheets that exhibit specified target deformation patterns. Thus, the present work provides a systematic and physically intuitive methodology applicable to arbitrary kinematic deformation and stiffness requirements.
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Soft Condensed Matter
Mechanics of heterogeneous fiber networks
Kyu Hwan Choi, Sattvic Ray, Reef Sweeney et al. (+2 more)
Internally generated active stresses drive soft materials into architectures inaccessible to thermal self-assembly. We use a microtubule-based active fluid to assemble and irreversibly restructure actin-fascin networks. Subsequently, we probe the mesoscale mechanics of such networks by combining active microrheology with fluorescence imaging of the strain field around the probe. Increasing motor concentration broadens the pore-size distribution and thickens load-bearing bundles, raising the mean local elastic modulus and its spatial variability. Displacement fields of actively-processed networks propagate over longer range when compared to unprocessed networks. At large strains, both networks strain soften and plastically restructure. The combined microrheology and strain-imaging approach show that tunable active stresses reprogram the structure and viscoelastic response of fiber networks at the scale of their structural heterogeneity.
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All authors Kyu Hwan Choi, Sattvic Ray, Reef Sweeney, Zvonimir Dogic, Sho C. Takatori
Soft Condensed Matter
Existent condition of partially wet state in capillary tubes
Chen Zhao, Jiajia Zhou and Masao Doi
We develop a theory that predicts the
equilibrium states of a fluid contained in a capillary which has corners. Each section of the tube can take three states: completely wet state where the tube section is completely occupied by the fluid, partially wet state where only the corners are occupied by the fluid known as corner film or finger, and completely dry state. We calculate the phase diagram of these states for a square tube with rounded corners. It is shown that the partially wet state can exist only in a certain region in the parameter space spanned by the
equilibrium contact angle and the corner
curvature.
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Statistical Mechanics
Random-h Fractional-Dimensional Lattices Reveal Endpoint-Compressed Percolation Activation between Two and Three Dimensions
Ran Huang
Non-integer dimensionality is central to fractal and complex systems, yet it is rarely represented as an explicit
lattice on which classical statistical-mechanical models can be directly simulated. Here we introduce random-h fractional dimension (RhFD), a constructive
lattice framework in which fractional-dimensional environments are generated by
stochastic activation of local connectivity, h. In the 2D-to-3D interval, RhFD
lattices are formed by recursively growing out-of-plane sites from a square base with probability h̊o}h. Using quenched site-percolation simulations, we show that the construction recovers the integer-dimensional endpoints and yields a robust crossover in which the percolation threshold decreases from the 2D regime toward the 3D regime. The crossover is not a uniform interpolation: high-resolution scans reveal endpoint-compressed activation, with -dpc/dh̊o}h increasing toward h̊o}h = 1. Mass dimension increases with h̊o}h, whereas the coordination descriptor first decreases as sparse protrusions form and then rises sharply when a dense 3D backbone emerges. RhFD provides an explicit
lattice substrate for fractional-dimensional statistical mechanics and shows that
geometric mass, local coordination, and critical connectivity can decouple during dimensional crossover.
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Materials Science · Cross-listed from physics.plasm-ph
Capturing many-body effects in electrical conductivity of warm dense matter
Brian P. Robinson, Alina Kononov, Lucas J. Stanek et al. (+3 more)
Conductivity models for warm dense matter inform simulations of planetary structure and fusion experiments. State-of-the-art conductivity calculations based on density functional theory approximate many-body physics and neglect electron-electron scattering lifetimes. We introduce a many-body framework for electrical conductivity using the GW approximation of the electronic self-energy. For beryllium, improved transition energies yield a surprisingly large reduction in low-temperature DC conductivity, while electron-electron scattering primarily reduces high-temperature DC conductivity.
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All authors Brian P. Robinson, Alina Kononov, Lucas J. Stanek, Andrew D. Baczewski, André Schleife, Stephanie B. Hansen
Strongly Correlated Electrons
Unbiased large-$N$ approach to competing vestigial orders of density-wave and superconducting instabilities
Grgur Palle and Rafael M. Fernandes
When a primary order breaks multiple
symmetries, partially ordered phases that only break a subset of those
symmetries, known as vestigial phases, may onset at a higher temperature. This concept has been applied to a wide range of systems, including iron pnictides, cuprates, van der Waals antiferromagnets, doped topological
insulators, and twisted
bilayer graphene. In general, a multicomponent primary order parameter (OP) supports multiple vestigial channels, each described by a quadratic (or higher-order) composite OP. However, the standard large-$N$ approach to the Ginzburg-Landau action of the primary OP has an intrinsic ambiguity in how one decouples the composite OPs, leading to situations in which one can seemingly enhance or eliminate altogether any vestigial instability. Here, we show that this ambiguity is a direct consequence of redundancy relations, such as Fierz identities, that relate different composite OPs, reflecting the fact that different vestigial channels interfere with each other and thus cannot be treated separately. To resolve this ambiguity, we propose an unbiased large-$N$ approach that respects both the redundancy relations and the underlying
symmetry-group structure, and that gives unique values for the effective interactions of all vestigial channels. Our analysis reveals the generic existence of regions in the parameter space of quartic Landau coefficients where no vestigial order is stable, in contrast to the standard large-$N$ approach, but in agreement with weak-coupling and variational approaches. We illustrate our results by analyzing the vestigial orders of charge-density waves,
spin-density waves, and multicomponent
superconductors in tetragonal, hexagonal, and cubic systems, respectively, revealing the presence of exotic vestigial phases describing
spin-quadrupolar, charge-$4e$ superconducting, and altermagnetic orders.
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Strongly Correlated Electrons · Cross-listed from physics.chem-ph
Low-rank compression of two-electron reduced density matrices
Kemal Atalar, Hugh G. A. Burton, Andreas Grüneis et al. (+1 more)
Two-body reduced density
matrices (2RDMs) encode the essential two-electron physics of electronic states, but their quartic storage cost poses a major limitation in practical workflows. We investigate a simple protocol to compress both transition and non-transition 2RDMs into a lower-rank representation that preserves their wedge-product structure and physical
symmetries under truncation. The resulting decomposition couples Coulomb and exchange channels through a common set of low-rank factors, yielding a more compact rank-sparse representation than single-channel factorizations. For correlated states, the effective rank scales linearly with system size, achieving a $\sim99$% compression for the coupled-cluster 2RDM of octane while retaining chemical accuracy. We apply this to the recently introduced ab initio eigenvector continuation workflows, where many-body wave functions are interpolated across
nuclear geometries with mean-field cost. Here, 2RDMs between training states act as projectors into a subspace but their
memory scaling limits applications to larger systems. The compression scheme reduces the
memory cost from quartic to quadratic for a fixed error per electron. Metrics to systematically control the decomposition are investigated, enabling statistically resolved structural, dynamical and spectroscopic observables from nonadiabatic molecular dynamics simulations of photoexcited H$_{28}$ chains, interpolating from compressed near-exact DMRG training data. This establishes these structure-preserving compressed intermediates for practical correlated electronic structure workflows.
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All authors Kemal Atalar, Hugh G. A. Burton, Andreas Grüneis, George H. Booth
Superconductivity · Cross-listed from quant-ph
Quantum tunneling, global phases and the limits of classical action reconstructions
Chong Qi and Mário B. Amaro
It was proposed recently that the Schrödinger wave function can be reconstructed exactly from a discrete superposition of classical action branches weighted by associated classical densities, without semiclassical approximations. We examine this construction for
quantum tunneling through finite potential barriers and for
quantum phase phenomena. Although formally consistent when the Hamilton-Jacobi equation admits globally defined real branches, the construction breaks down in classically forbidden regions where no real classical action exists. Using rectangular and Coulomb barrier tunneling in alpha decay and
nuclear fusion, we show that the wave function requires either a non-vanishing
quantum potential or complex-valued action. The growing barrier component fixed by global boundary conditions is essential for transmission and cannot arise from local real classical trajectories alone. Berry phase, flux quantization, Josephson tunneling, and dc SQUID interference likewise impose global phase constraints absent from local classical action transport.
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Mesoscale and Nanoscale Physics
Optical signatures of antiferromagnetic correlations in a strongly interacting quantum Hall MoSe2 monolayer
Jiho Sung, Pavel A. Volkov, Ilya Esterlis et al. (+9 more)
Strong
magnetic fields quench the kinetic energy of electrons, leading to the formation of flat energy bands, known as Landau levels (LLs). In this situation, even weak interactions can drive the emergence of various ordered phases. The simplest of such phases is a
quantum Hall ferromagnet, where a spontaneous
spin polarization emerges when LLs with opposite
spins cross. The presence of strong electron-electron interaction at zero field changes this picture and makes the resulting states much harder to predict. Here we use magneto-optical spectroscopy to reveal
quantum Hall states with unconventional correlations favouring an unpolarized state in the strongly correlated electron
liquid in a MoSe2 monolayer. The oscillations of the
exciton polaron energies as a function of perpendicular
magnetic field and electron density demonstrate the emergence of LLs in a correlated electron
liquid and density-dependent crossings between LLs of opposite valleys. On lowering the LL filling factor, where interactions within LLs are stronger, the crossings systematically broaden, indicating an increase in the Zeeman energy required to fully polarize the valley-degenerate LLs. These observations are shown to be consistent with
antiferromagnetic interactions between LL electrons, favouring a ground state with zero valley polarization, and are therefore inconsistent with conventional
quantum Hall ferromagnetism. This discovery demonstrates a qualitatively distinct form of
quantum Hall magnetism in a strongly correlated electron
liquid, establishing an anchoring point for understanding
spin-unpolarized fractional and ordered states of correlated electrons driven by
magnetic field.
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All authors Jiho Sung, Pavel A. Volkov, Ilya Esterlis, Jue Wang, Luke N. Holtzmann, Takashi Taniguchi, Kenji Watanabe, Katayun Barmak, James Hone, Mikhail D. Lukin, Philip Kim, Hongkun Park
Quantum Gases
Giant critical response in a driven-dissipative quantum gas
Ross C. Schofield, Daniel Lim, Himadri S. Dhar et al. (+6 more)
Systems close to a phase transition turn weak perturbations into large responses. At
equilibrium, this amplification is closely linked to criticality: fluctuations grow, dynamics slow, and a common soft mode controls the response. Whether this correspondence survives in driven-dissipative
quantum systems, sustained by continuous pumping and loss away from thermal
equilibrium, remains an open question. Here we show experimentally that it does. In a room-temperature
semiconductor photon Bose-Einstein condensate, the critical slowing of spontaneous intensity fluctuations and the amplification of weak pump perturbations are measured independently. Both peak at the same condensate population, $\bar{n}_c = 1250$, where the dimensionless slowing factor and susceptibility reach the same value, $\bar{n}_c/2 = 625$. A single weakly damped collective
photon-reservoir mode governs both effects. This fluctuation-response correspondence in a finite open
quantum gas establishes critical susceptibility as a measurable dynamical signature of condensation, with peak gain set by system size.
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All authors Ross C. Schofield, Daniel Lim, Himadri S. Dhar, Robert A. Nyman, Akshay K. Verma, Edmund Clarke, Jon Heffernan, Florian Mintert, Rupert F. Oulton
Superconductivity · Cross-listed from nucl-th
The mean-field theory of superfluid-superconducting vortex states in the outer core of neutron stars
Dmitry Kobyakov
Purpose: Characterize superfluid-superconducting
vortex states at arbitrary pressures with $T_{cp}\neq T_{cn}$, assuming both
proton and
neutron mean-fields are formed by
spin-0 Cooper pairs. Method: The existing mean-field theory is extended to account for $T_{cp}\neq T_{cn}$. The pressure dependence of the pairing gap energy $\Delta_{\alpha0}$ is quantitatively established on the basis of the effective
chiral field theory. To link $T_{c\alpha}$ with $\Delta_{\alpha0}$, I use the weak-coupling result $T_{c\alpha}\approx0.57\Delta_{\alpha0}$. A quadratic scaled-temperature ($T/T_{cp}$) dependence of the thermodynamic
magnetic field is postulated in analogy with pure
superconductors. The $T/T_{c\alpha}$-dependence of the gap $\Delta_{\alpha T}$ is inferred from the many-body approximations for the pure
neutron matter. Results: An empirical $T/T_{c\alpha}$-dependence for the mean-field is constructed to account for the interplay between the condensation and the
magnetic energies. The superfluid entrainment is found to increase the size of the
vortex core and to decrease the effective
magnetic penetration depth. The size of the
neutron vortex core is found to be larger than the
magnetic penetration depth in the outer core. Conclusions: The usual approximation of infinitely thin
vortex line (the London's approximation) for the
neutron vortex is found to be irrelevant in the entire outer core and for the
proton vortex is found to be limited to vicinity of the crust-core transition. The developed mean-field theory paves the way to study the
vortex microscopic structure, the angular momentum, the magnetization and the
vortex-fluxtube interaction energy.
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Superconductivity
First-principles real-space embedding theory of the superconducting proximity effect
Nicolas Baù, Mitra Dowlatabadi, Tommaso Chiarotti et al. (+2 more)
When a
superconductor is placed in contact with a normal material, Cooper pairs penetrate the latter and induce superconductivity via the proximity effect. Despite its central role in
quantum materials, superconducting devices and topological platforms, a predictive first-principles description of the proximity effect at realistic interfaces has remained computationally prohibitive so far. Here, we fill this gap by developing a Green's-function framework based on real-space dynamical
embedding that enables first-principles simulations of superconducting proximity in mesoscopic systems. We show that the proximity effect admits a transparent diagrammatic formulation in terms of normal and anomalous
embedding self-energies, which disentangle and quantify the distinct renormalization mechanisms generated by coupling to a superconducting bath. By combining this formalism with recursive schemes, we compute local spectral functions and proximity lengths extending over hundreds of nanometers into the bulk without resorting to thick interface slabs. We deploy the approach on tight-binding models (Qi-Hughes-Zhang and Fu-Kane-Mele), where we analyze mixed-parity superconductivity in topological
insulators proximitized by $s$-wave
superconductors, and on first-principles simulations of NbSe$_2$/CrBr$_3$
heterostructures based on density-functional theory and maximally-localized Wannier functions, the latter enabling direct comparison with scanning tunneling spectroscopy experiments. Our work provides a scalable and conceptually unified framework that bridges microscopic electronic structure and mesoscale proximity physics, enabling predictive atomistic simulations of superconducting interfaces.
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All authors Nicolas Baù, Mitra Dowlatabadi, Tommaso Chiarotti, Massimo Capone, Antimo Marrazzo
Mesoscale and Nanoscale Physics
Zijian Zhou, Ran Jing, Heng Wang et al. (+3 more)
Hyperbolic polaritons are conventionally associated with structural anisotropy or phononic Reststrahlen bands. Here, we predict a new class of
hyperbolic polaritons arising from
magnetic-field-induced cyclotron motion of charge carriers. When a perpendicular
magnetic field is applied to high-mobility semimetals, the cyclotron response drives the in-plane dielectric function from metallic- to insulating-like below the cyclotron resonance frequency, while the out-of-plane response remains metallic. This anisotropy creates a
hyperbolic dielectric environment that supports field-tunable
hyperbolic polaritons. We develop a comprehensive theoretical framework incorporating coupling to other collective excitations and show that these modes can be directly visualized in real space via terahertz near-field nanoscopy. Our work identifies cyclotron motion as a new route to
hyperbolic polaritons and establishes a versatile platform for magnetically programmable nanophotonics.
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All authors Zijian Zhou, Ran Jing, Heng Wang, Lukas Wehmeier, Mengkun Liu, Bing Cheng
Materials Science
Symmetry Guided Band-Gap Opening via Periodic Topological Defects in Graphene
D. N. Garzon, Leonel Cabrera-Loor, Jacopo Gliozzi et al. (+3 more)
Graphene lacks an intrinsic band-gap, which limits its use in electronic applications. Here we demonstrate that periodic arrays of topological defects can open and control a band-gap in a predictable manner governed by defect spacing and
lattice symmetry. Using first-principles density functional theory calculations supported by tight-binding models, we investigate
graphene superlattices containing Stone-Wales and flower-like defects over a range of $N \times N$ periodicities, where $N$ determines the defect separation. We show that band-gap opening occurs only when translation
symmetry is reduced in a specific way: for supercells with $N$ a multiple of three, Brillouin-zone folding brings the Dirac cones at $K$ and $K'$ to the same momentum in the reduced Brillouin zone. In particular, flower-like defect superlattices produce larger and tunable band-gaps, whose magnitude decreases systematically with increasing defect separation and approaches zero in the dilute-defect limit. These results establish a predictive framework for band-gap engineering in defect-patterned
graphene and clarify the microscopic mechanism underlying gap formation in periodically reconstructed
lattices.
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All authors D. N. Garzon, Leonel Cabrera-Loor, Jacopo Gliozzi, Marco Fronzi, Catherine Stampfl, Henry P. Pinto
Materials Science
Synergistic doping of the grain interior and grain boundary alters deformation mechanisms and enables extreme strength in nanocrystalline Ni-Cr-Y alloys
Yi Liu, Jason R. Trelewicz and Timothy J. Rupert
Solid solution addition and grain boundary segregation have been independently shown to enhance the strength of nanocrystalline
alloys. In the present study, the interplay between these two effects is investigated in nanocrystalline Ni-Cr-Y sputtered films through systematic variation of alloying element contents with grain size kept constant. Cr is introduced into a solid solution and serves to strengthen the
lattice, while Y segregates to the grain boundaries to stabilize these features. Nanoindentation is used to probe hardness, with unexpected trends and very high values observed. Cr additions led to nanocrystalline solid solution strengthening, yet saturation was observed at higher concentrations due to the emergence of grain boundary dominated processes, as evidenced by pile-up morphologies containing slip steps and grain rotation. Y enrichment was observed at the examined grain boundaries, enhancing boundary-mediated strengthening by pinning the dislocations and suppressing dislocation emission, grain boundary sliding, and grain rotation processes. With increasing Y concentration, the nanocrystalline solid solution strengthening effect induced by Cr addition becomes weaker. This phenomenon can be attributed to a reduced dislocation bowing distance caused by dopant pinning. Most notably, the strongest ternary Ni-Cr-Y
alloy exhibited a hardness of 11.0 GPa, among the highest hardness values reported for single-phase nanocrystalline Ni
alloys with grain sizes near 20 nm. These findings highlight how tuning grain and grain boundary chemistry offers a viable strategy to control dislocation mechanics and improve the strength of nanocrystalline metals.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Plasmon exciton coupling enhances second order nonlinear response in borophene ZnO hybrid structures
Maximilian Black, Yaser Abdi, Prabhdeep Singh et al. (+7 more)
Nonlinear optical processes in low dimensional materials are often weak or
symmetry forbidden, limiting their use in nanoscale light sources and on chip frequency conversion. Here, we show that combining two weakly nonlinear systems, anisotropic borophene and excitonic zinc
oxide, yields an enhanced and resonant nonlinear response. In borophene ZnO
heterostructures, cathodoluminescence reveals a two orders of magnitude enhancement at 400 nm and 800 nm, due to an enhanced two
photon absorption process. Under tunable near infrared excitation, a clear second harmonic signal emerges with quadratic power dependence and strong resonance near 800 nm. We attribute this to nonlinear plasmon
exciton coupling, which reshapes the excitonic response and enables efficient hybrid pathways for frequency conversion. These results establish anisotropic plasmon
exciton hybridization as a route to controlling nonlinear optical responses in low dimensional
heterostructures.
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All authors Maximilian Black, Yaser Abdi, Prabhdeep Singh, Bharti Garg, Zahra Alavi, Mohammadreza Alikhanim, Mohammad Hossein Salemi Seresht, Fatemeh Chahshouri, Masoud Taleb, Nahid Talebi
Mesoscale and Nanoscale Physics
Bound States in Second-order Topological Graphitic Structures
Haiyue Huang, Prineha Narang and Ioannis Petrides
Quadrupole
insulators are a class of second-order topological
insulators (SOTIs) that host zero-dimensional corner states within a two-dimensional bulk. Despite their unique properties, their realization in electronic systems on realistic material platforms remains rare. In this work, we present a general design principle to obtain quadrupole
insulators based on two-dimensional graphitic structures. By engineering the positions and connections of zigzag edges, we identify four topological classes of graphitic structures. We show that topologically protected massless corner state emerge at the intersection of domains belonging to different topological classes. Crucially, by tuning the smoothness of the domain wall, we further demonstrate the appearance of additional massive localized states with non-zero angular momentum. Our results provide a practical framework for realizing experimentally accessible SOTIs and uncover the coexistence of both massless and massive bound states in two dimensions.
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Statistical Mechanics · Cross-listed from quant-ph
Lecture Notes on Replica Tensor Networks for Random Quantum Circuits
Xhek Turkeshi
We present a pedagogical, hands-on tutorial on replica tensor-network techniques for random
quantum circuits. At its core, the method recasts
circuit-averaged observables acting on multiple copies of the system as the contraction of a classical tensor network, equivalently the partition function of a statistical-mechanics model whose effective
spins live in the commutant of the gate ensemble. The framework is general: changing the observable or the initial state modifies only the replica boundary conditions, while changing the ensemble modifies the bulk tensors. Focusing on
quantum-information diagnostics, from metrics of wavefunction spreadings to
entanglement quantifiers, we illustrate the approach in both clean and noisy random
unitary circuits. We then briefly explain how the methodology extends to other ensembles, such as orthogonal or Clifford
circuits. The lecture notes are accompanied by ReplicaTN, a self-contained C++/Python library and pedagogical notebooks.
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Quantum Gases
BCS-BEC crossover in trapped one-dimensional Fermi-Hubbard chains: entanglement and correlation signatures from DMRG and effective-pairing theory
G. Diniz, I. M. Carvalho, M. Sanino et al. (+2 more)
Confined ultracold atoms in optical
lattices provide a versatile platform for simulating
lattice models of strongly correlated
quantum systems, where pairing phenomena and superfluid phases can be explored under controlled conditions. While the crossover between the Bardeen-Cooper-Schrieffer (BCS) phase and the Bose-Einstein condensation (BEC) is well understood in homogeneous systems, spatial confinement breaks translational
symmetry and reshapes correlation patterns, making the BCS-BEC identification in trapped geometries challenging and allowing unconventional phases to emerge with no direct analog in homogeneous systems. Here we present a characterization of the BCS-BEC crossover in harmonically confined one-dimensional
Fermi-Hubbard chains. Our analysis combines Density
Matrix Renormalization Group (DMRG) simulations and
entanglement-based diagnostics with effective models describing the formation of tightly bound
fermion pairs. This combined approach enables a detailed understanding of how the interplay between interactions and confinement reshapes the crossover, leading to insulating regions coexisting with persistent superfluid correlations. Within this framework, we further introduce conditioned correlation functions whose power-law decay allows a clear distinction between BCS-like and BEC-like regimes. The consistency between the effective descriptions and the numerical DMRG results yields a unified picture of the crossover in harmonically confined geometries.
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All authors G. Diniz, I. M. Carvalho, M. Sanino, F. Iemini, V. V. França
Statistical Mechanics
Field Theory of Data: Anomaly Detection via the Functional Renormalization Group. The 2D Ising Model as a Benchmark
Riccardo Finotello, Vincent Lahoche, Parham Radpay et al. (+1 more)
We establish a correspondence between anomaly detection in high-noise regimes and the renormalization group flow of non-
equilibrium field theories. We provide a physical grounding for this framework by proving that the detection of phase transitions in interacting non-
equilibrium systems maps to the study of an effective
equilibrium field theory near its Gaussian fixed point, which we identify with the universal Marchenko-Pastur distribution. Applying the Functional Renormalization Group to the two-dimensional Model A, we demonstrate that the noise-to-signal ratio acts as a physical temperature, where the signal emerges as ordered domains within a thermalized background of fluctuations. Using the exact Onsager solution as a
benchmark, we show that this approach identifies critical thresholds with an error below 4%, significantly outperforming standard information-theoretic metrics such as the Kullback-Leibler divergence. Our results provide a universal strategy for resolving structures in complex
datasets near criticality, bridging the gap between statistical mechanics and statistical inference.
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All authors Riccardo Finotello, Vincent Lahoche, Parham Radpay, Dine Ousmane Samary
Mesoscale and Nanoscale Physics
Photon Momentum Enabled Symmetry Breaking and Nonlinear Photocurrents in the Centrosymmetric Dirac Semimetal PdTe
Sambhu G Nath, Subhadip Manna, R K Gopal et al. (+1 more)
In centrosymmetric Dirac semimetals, second order nonlinear photocurrents are forbidden by the coexistence of time-reversal and inversion
symmetries. Here, we demonstrate that finite
photon momentum transfer acts as a dynamic
symmetry breaking mechanism in PdTe, enabling nonlinear optical responses that are nominally forbidden in the centrosymmetric bulk. Through polarization sensitive measurements, we resolve distinct contributions from the circular photogalvanic effect (CPGE),
geometric shift currents, and
photon drag mediated processes. We show that the helicity dependent current vanishes at normal incidence and reverses sign with the angle of incidence, reflecting the coupling between
photons and
spin polarized surface states. Crucially, thickness dependent analysis reveals that the helicity dependent photocurrent component C scales with film thickness, establishing a robust bulk contribution enabled by momentum transfer. This confirms that incident
photons provide the directional axis required to probe interband
quantum geometry, rather than the response originating solely from surface states or strain. Our results demonstrate that optical excitation can dynamically reduce the effective
symmetry of the system, enabling access to
quantum geometric tensors and establishing PdTe as a promising platform for exploring nonequilibrium dynamics governed by
photon momentum in high
symmetry topological materials.
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All authors Sambhu G Nath, Subhadip Manna, R K Gopal, Chiranjib Mitra
Strongly Correlated Electrons
Contrasting structural reversibility and magnetic correlations in isostructural honeycomb magnets CrCl$_3$ and $\alpha$-RuCl$_3$
Zachary Morgan, Iris Ye, Jiasen Guo et al. (+2 more)
We report a comparative
neutron single
crystal diffraction study of the structural and
magnetic properties of layered halides CrCl$_3$ and $\alpha$-RuCl$_3$, which host a honeycomb arrangement of transition metal ions with distinct electronic configurations and undergo a first-order structural transition between high-temperature C2/m and low-temperature R$\bar{3}$. Both compounds show a step-like change in the $c$-
lattice, consistent with an expected stacking rearrangement. In contrast, the in-plane
lattice response is quite different: $\alpha$-RuCl$_3$ exhibits an abrupt hysteretic change across the transition accompanied by progressive crystalline degradation upon thermal cycling, whereas CrCl$_3$ shows a smooth in-plane
lattice evolution and remains structurally robust. Magnetically, CrCl$_3$ orders into an A-type
antiferromagnetic structure at T$_N$=14\,K and exhibits pronounced diffuse
magnetic scattering extending up to about 40\,K. $\alpha$-RuCl$_3$ shows no observable
magnetic diffuse scattering above its zig-zag
antiferromagnetic ordering temperature T$_N$=7.6\,K. These results suggest that the contrasting structural and
magnetic behaviors arise from an interplay between interlayer sliding energetics and the fundamentally different electronic configurations of the two compounds.
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All authors Zachary Morgan, Iris Ye, Jiasen Guo, Michael A McGuire, Jiaqiang Yan
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Permutation-symmetric quantum trajectories
Elliot W. Lloyd, Aleksandra A. Ziolkowska and Jonathan Keeling
We show how one may perform a
stochastic unravelling which respects weak permutation
symmetry for general models of $N$ emitters coupled to a common system (e.g. a cavity mode). Our work extends prior work by Zhang et al. [2018 New J. Phys. 20 112001] which provided an efficient
quantum jump approach for a restricted subset of such problems. For problems involving $2$-level emitters, such an unravelling reduces the computational cost from $\mathcal{O}(N^5)$ to $\mathcal{O}(N^2)$, and with additional refinements, allows reduction to $\mathcal{O}(N)$. This significantly increases the range of system sizes for which one can model exact
quantum dynamics of such systems. We further show how the method can also be applied to $d$-level systems, with computational effort scaling as $\mathcal{O}(N^{d(d-1)/2})$, and we show it allows large-$N$ simulations for $d=3$.
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Materials Science
Application of the exact-factorization density-functional perturbation approach to pentacene crystal and monolayer MoS2
Rachel Steinitz-Eliyahu, Galit Cohen, Guy Vosco et al. (+3 more)
Non-adiabatic effects arising from electron-
phonon interactions are often neglected within the Born-Oppenheimer (BO) approximation, which assumes that electronic states adjust instantaneously to
nuclear motion. The exact factorization (EF) formalism provides a rigorous framework for treating such effects beyond the adiabatic regime and has recently been adapted to density functional theory (DFT) in the harmonic limit. Building on these foundations, we previously introduced an EF-based perturbative scheme, the EF density-functional perturbation theory (EF-DFPT), that enables the computation of
phonon-driven non-adiabatic (NA) corrections to Kohn-Sham (KS) electronic states, up to second order in
nuclear displacements. Here, we present the first implementation and application of EF-DFPT to extended periodic materials, focusing on its impact on experimentally relevant observables. Using the pentacene molecular
crystal and monolayer MoS2 as representative soft- and stiff-mode systems, respectively, we demonstrate how NA electron-
phonon interactions modify the static dielectric response. We show that these modifications originate from the combined effect of NA
phonon-dressed electronic wavefunctions and second-order NA energy renormalizations. The resulting behavior is strongly material dependent: NA effects are negligible in monolayer MoS2, whereas in pentacene they lead to pronounced long-range screening effects associated with soft vibrational modes and enhanced electron-
phonon coupling.
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All authors Rachel Steinitz-Eliyahu, Galit Cohen, Guy Vosco, E.K.U. Gross, Ryan Requist, Sivan Refaely-Abramson
Mesoscale and Nanoscale Physics
Valley-Controlled Viscosity of Two-Dimensional Dirac Fluids
Alexey Ermakov and Alessandro Principi
Motivated by recent experiments in weakly hybridized small-angle twisted
bilayer graphene, we investigate how valley imbalance affects the viscosity of two-dimensional Dirac fluids. We show that shifting the two low-energy Dirac cones relative to one another provides a direct knob to control the viscosity of the electron fluid. As the splitting is increased, the system passes through distinct transport regimes associated with valley depletion, charge-neutrality crossover, and the onset of electron-hole scattering, producing a pronounced nonmonotonic response. To place this result in context, we also analyze the viscosity in monolayer
graphene (MLG) and two-dimensional electron gas (2DEG). We show that, due to the strong dependence of its inertial mass density on temperature, the kinematic viscosity of MLG is a monotonically decreasing function of temperature. Our results identify valley control as a route to tuning hydrodynamic transport in Dirac materials and clarify the interplay between band structure, scattering phase space, and screening in setting the viscous response.
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Mesoscale and Nanoscale Physics
Shubhanshu Karoliya, Ekta and Gargee Sharma
The unambiguous identification of topological Majorana-bound states (MBSs) in superconducting hybrid systems is hindered by trivial low-energy excitations, especially partially separated Andreev bound states (psABSs), which can mimic Majorana signatures. Here we show that spatially nonuniform strain offers a systematic route to control and interconvert these low-energy states. Using tight-binding Bogoliubov–de Gennes simulations, we study one-dimensional
semiconductor nanowires and
graphene nanoribbons with superconductivity, Rashba
spin-orbit coupling, Zeeman fields, and disorder. We find that even weak strain can qualitatively reshape the low-energy spectrum by modifying effective band parameters and redistributing wavefunction weight. In nanowires, strain tunes the spatial overlap of Majorana components and shifts the topological phase boundary, enabling controlled crossovers between trivial states, psABSs, and topological MBSs. In
graphene nanoribbons, where multiband effects and edge states produce a dense, hybridized low-energy spectrum, strain suppresses subband mixing, lifts degeneracies, and stabilizes boundary-localized modes. In both platforms, we identify regimes where disorder-induced psABSs are converted into well-separated and robust MBSs through strain-enhanced nonlocality. We further develop an analytical framework based on a position-dependent topological mass and strain-driven domain-wall motion, which captures the physical mechanism of these crossovers and yields a real-space criterion for the emergence and stability of Majorana modes. Our results establish strain as an effective tuning parameter for distinguishing and stabilizing topological MBSs in realistic disordered systems, and suggest an experimentally relevant pathway toward improved control and identification of Majorana modes in complex hybrid structures relevant to topological
quantum computation.
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Materials Science
Adamantane plasma polymers: fluorine-free vacuum-processable triboelectric thin films for all-triboelectric nanogenerator configurations
Gloria P. Moreno-Martinez, Fernando Nunez-Galvez, Hari Krishna Mishra et al. (+12 more)
Triboelectric nanogenerators (TENGs) are major drivers in on-site power generation for smart devices, enable self-powered sensors, and introduce novel catalytic processes. Here, we present the advantages of adamantane
plasma layers as bivalently triboelectric surfaces capable of exhibiting both tribopositive and tribonegative character through simple modification of the synthesis conditions without the need for additives or functionalization. Fabrication facing or backfacing the
plasma yields thin film
polymers with different dielectric constants, Young's
moduli, and secondary electron emission. The conformality, stability, and processability of the
polymers enable direct implementation across solid-solid, solid-
liquid, and hybrid piezo-triboelectric configurations. Additional texturization by buckling is shown to provide voltage and current outputs as high as 90 V cm2 and 0.6 uA for a 2.8 um (tribonegative) vs. 400 nm (tribopositive) combination. A maximum power density of 2.1 uW cm-2 is generated from salty droplets in a switch-electrode drop-TENG configuration employing a 500 nm-thick tribopositive adamantane
polymer as the triboelectric surface. These layers have demonstrated outstanding durability, enabling more than 10^5 cycles in solid-solid nanogenerators and 10^4 droplet impacts in solid-
liquid configurations. The synthetic method is environmentally friendly and industrially scalable, making the adamantane
plasma polymer a reliable and competitive solution for thin film triboelectric materials.
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All authors Gloria P. Moreno-Martinez, Fernando Nunez-Galvez, Hari Krishna Mishra, Triana Czermak, Xabier Garcia-Casas, Vanda Cristina Godinho, Bernd Wicklein, Juan Carlos Sanchez-Lopez, Javier Ferrer, Isabel Montero, Juan Ramon Sanchez-Valencia, Andris Sutka, Francisco Aparicio, Angel Barranco, Ana Borras