Mesoscale and Nanoscale Physics
Fano profile in the resonance fluorescence spectrum of a solid-state quantum emitter coupled to phonons
Rafal A. Bogaczewicz and Pawel Machnikowski
We present a theory of resonance fluorescence (RF) of a solid-state
quantum emitter in the regime of weak optical excitation. The emitter is coupled to the
phonon modes of the surrounding bulk
semiconductor, described by a super-Ohmic spectral density. We show that the RF spectrum of this system consists of a central elastic line, a broad
phonon sideband known from other linear and non-linear spectra of such systems, and a narrow inelastic contribution characteristic of scattering spectra, stemming from noise-induced transient dynamics. At moderate
phonon couplings or low temperatures, the interplay between the broad sideband and the inelastic feature leads to a Fano-like profile near the resonant energy with the Fano parameter determined by
laser detuning. In the weak-coupling limit (where only single-
phonon processes are included), the spectrum becomes an exact Fano shape, with the inelastic component vanishing completely at the exact
laser frequency. The amplitude of this spectral feature grows linearly with temperature, while its width depends solely on the spontaneous emission rate of the emitter. Because the spectral line shape is extremely sensitive to dephasing, resonance fluorescence can serve as a direct, non-interferometric probe of coherence at dephasing rates critical for generating highly indistinguishable single
photons. We relate the
quantum character of the reservoir to the non-commutativity of noise observables and show that the Fano resonance persists in the classical (commutative) limit. We also discuss how the redistribution of optical coupling efficiency between the central line and the sidebands affects the total scattering rate under various excitation conditions.
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Strongly Correlated Electrons
Measuring the Hall effect in hysteretic materials
Jaime M. Moya, Anthony Voyemant, Sudipta Chatterjee et al. (+4 more)
Measurement of the
Hall effect is a ubiquitous probe for materials discovery, characterization, and metrology. Inherent to the
Hall measurement geometry, the measured signal is often contaminated by unwanted contributions, so the data must be processed to isolate the
Hall response. The standard approach invokes Onsager-Casimir reciprocity and antisymmetrizes the raw signal about zero applied
magnetic field. In hysteretic materials this becomes nontrivial, since Onsager-Casimir relations apply only to microscopically reversible states. Incorrect antisymmetrization can lead to artifacts that mimic anomalous or topological
Hall signatures. The situation is especially subtle when hysteresis loops are not centered at zero applied field, as in exchange-biased systems. A practical reference for generically extracting the
Hall response in hysteretic materials is lacking. Here, using Co$_3$Sn$_2$S$_2$ as a bulk single-
crystal model that can be prepared with or without exchange-biased hysteresis, we demonstrate two procedures that can be used to extract the
Hall effect: (1) reverse-
magnetic-field reciprocity and (2) antisymmetrization with respect to applied field. We then measure the
Hall effect on CeCoGe$_3$, a noncentrosymmetric antiferromagnet which can be prepared to have asymmetric magnetization and magnetoresistance, and demonstrate how improper processing can generate artificial anomalous
Hall signals. These methods are generic and can be applied to any conductor.
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All authors Jaime M. Moya, Anthony Voyemant, Sudipta Chatterjee, Scott B. Lee, Grigorii Skorupskii, Connor J. Pollak, Leslie M. Schoop
Materials Science
Colloquium: A critique on van der Waals and two-dimensional magnets
Johann Coraux, Nicolas Rougemaille, Cedric Robert et al. (+6 more)
Magnetic two-dimensional (2D)
crystals were isolated about a decade ago, triggering a tremendous research activity worldwide. This colloquium raises a stiff question: what is really new about them? At first sight, they seem to be purer implementations of 2D
spin models than traditional systems such as ultra-thin films. Yet, they partly realized their promises so far, and whether they give fresh perspectives on long-standing predictions in statistical physics is still an open question. Undoubtedly, they are uniquely amenable to electric-field effect, susceptible to mechanical deformation, and sensitive to moirés, for example. They represent interesting platforms for exploring, challenging, or simply revisiting a wide range of phenomena in condensed matter magnetism. This colloquium intends to offer a critical, yet not necessarily skeptical, overview of the field, clarifying what we believe could be unique with 2D magnets, related quasi-2D van der Waals magnets, and their
heterostructures.
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All authors Johann Coraux, Nicolas Rougemaille, Cedric Robert, Clément Faugeras, Andrès Saul, Benoît Grémaud, Luis Hueso, Félix Casanova, Aurélien Manchon
Statistical Mechanics
Kinetic theory of pattern formation in a generalized multi-species Vicsek model
Eloise Lardet, Letian Chen and Thibault Bertrand
The theoretical understanding of pattern formation in active systems remains a central problem of interest. Heterogeneous flocks made up of multiple species can exhibit a remarkable diversity of collective states that cannot be obtained from single-species models. In this paper, we derive a kinetic theory for multispecies systems of self-propelled particles with (anti)
alignment interactions. We summarize the numerical results for the binary system before employing linear stability analysis on the coarse-grained system. We find good agreement between theoretical predictions and particle simulations, and our kinetic theory is able to capture the correct lengthscale in the emergent coexistence phases through a Turing-
Hopf instability. Extending the kinetic framework to multispecies systems with cyclic
alignment interactions, we recover precisely the same emergent ordering as corresponding simulations of the microscopic model. More generally, our kinetic theory provides an extensible framework for analyzing pattern formation and collective order in multispecies active matter systems.
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Materials Science
Ab initio prediction of strain-tunable spin defects in quasi-1D TiS3 and NbS3 nanowires
Jordan Chapman, Arindom Nag, Thang Pham et al. (+1 more)
Defects in atomically thin van der Waals materials have recently been investigated as sources of
spin-
photon entanglement with sensitivity to strain tuning. Unlike many two-dimensional materials, quasi-one-dimensional materials such as transition metal trichalcogenides exhibit in-plane anisotropy resulting in axis-dependent responses to compressive and tensile strains. Herein, we characterize the tunable
spin and optical properties of intrinsic vacancy defects in titanium trisulfide (TiS3) and niobium trisulfide (NbS3) nanowires. Within our ab initio approach, we show that sulfur vacancies and divacancies (VS and VD , respectively) in TiS3 and NbS3 adopt strain-dependent defect geometries between in-plane strains of -3 % and 3 %. The calculated electronic structures indicate that both VS and VD possess in-gap defect states with optically bright electronic transitions whose position relative to the conduction and valence bands varies with in-plane strain. Further, our calculations predict that VS in TiS3 and VD in NbS3 exhibit transitions in their ground state
spins; specifically, a compressive strain of 0.4 % along the direction of nanowire growth causes a shift from a triplet state to a singlet state for the VS defect in TiS3, whereas a tensile strain of 2.9 % along the same direction in NbS3 induces a triplet ground state with a zero-
phonon line of 0.83 eV in the VD defect. Our work shows that the anisotropic geometry of TiS3 and NbS3 nanowires offers exceptional tunability of optically active
spin defects that can be used in
quantum applications.
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All authors Jordan Chapman, Arindom Nag, Thang Pham, Vsevolod Ivanov
Disordered Systems and Neural Networks
Tree tensor networks for many-body localization in two dimensions
Lars Humpert, Dante M. Kennes and Jan-Niklas Herre
We investigate the disordered
spin-$\frac12$Heisenberg model in two dimensions and employ tree tensor networks (TTNs) with a physics-informed structural optimization of the tree layout, to simulate dynamics in the many-body localization problem. We find that TTNs are able to capture two-dimensional
entanglement patterns more effectively than
matrix product states (MPS) while being more efficient to contract than projected entangled pair states (PEPS) to probe larger systems and longer times. Structural optimization of the trees based on time
evolution of the
entanglement in the system allows to keep the necessary bond dimensions low and to maximally exploit the increased expressiveness of TTNs over MPS. In this way, we achieve more accurate results in all considered parameter regimes both below and above the ergodicity-to-localization crossover at a comparable compute-time cost.
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Materials Science
Anomalous lattice specific heat and rattling phonon modes in quadruple perovskites
Valentin Yu. Irkhin, Zhehong Liu, Danil A. Myakotnikov et al. (+3 more)
Experimental data on the specific heat $C_p$ of quadruple perovskites ACu$_3$Fe$_2$Re$_2$O$_{12}$ (A = Mn, Cu, La, Ce, Dy) are presented, demonstrating an anomalous concave-down $C_p/T$ vs. $T^2$ curve and a bell-shaped feature in $\beta(T) = (C_p - \gamma T)/T^3$ plotted against $T$ on a logarithmic scale. This feature is most pronounced for A = Cu and Mn. These findings can be explained by the rattling phenomenon, previously identified in other systems such as filled skutterudites and $\beta$-pyrochlores. Using first-principles DFT+U calculations, the presence of a rattling mode in A = Mn system is directly confirmed. A qualitative interpretation of the rattling mechanism in terms of a pseudo-Jahn-Teller effect is proposed.
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All authors Valentin Yu. Irkhin, Zhehong Liu, Danil A. Myakotnikov, Evgenia V. Komleva, Youwen Long, Sergey V. Streltsov
Superconductivity
Superconductivity in Electron Liquids: Precision Many-Body Treatment of Coulomb Interaction
Xiansheng Cai, Tao Wang, Shuai Zhang et al. (+5 more)
More than a century after discovery, the theory of conventional superconductivity remains incomplete. While the importance of electron-
phonon coupling is understood, a controlled first-principles treatment of Coulomb interaction is lacking. Current ab initio calculations of superconductivity rely on a phenomenological downfolding approximation, replacing Coulomb interaction with a repulsive pseudopotential \mu*, and leaving ambiguities in electron-
phonon coupling with dynamical Coulomb interactions unresolved. We address this via an effective field theory approach, integrating out high-energy electronic degrees of freedom using variational Diagrammatic Monte Carlo. Applied to the uniform electron gas, this establishes a microscopic procedure to implement downfolding, define the pseudopotential, and express dynamical Coulomb effects on electron-
phonon coupling via the electron vertex function. We find the bare pseudopotential significantly larger than conventional values. This yields improved pseudopotential estimates in simple metals and tests density functional perturbation theory accuracy for effective electron-
phonon coupling. We present an ab initio workflow computing superconducting Tc from the anomalous vertex's precursory Cooper flow. This infers Tc from normal state calculations, enabling reliable estimates of very low Tc (including near
quantum phase transitions) beyond conventional reach. Validating our approach on simple metals without empirical tuning, we resolve long-standing discrepancies and predict a pressure-induced transition in Al from superconducting to non-superconducting above ~60GPa. We propose ambient-pressure Mg and Na are proximal to a similar critical point. Our work establishes a controlled ab initio framework for electron-
phonon superconductivity beyond the weak-correlation limit, paving the way for reliable Tc calculations and novel material design.
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All authors Xiansheng Cai, Tao Wang, Shuai Zhang, Tiantian Zhang, Andrew Millis, Boris V. Svistunov, Nikolay V. Prokof'ev, Kun Chen
Other Condensed Matter
Berry phase polarization and orbital magnetization responses of insulators: Formulas for generalized polarizabilities and their application
J. W. F. Venderbos
Condensed matter physics is often concerned with determining the response of a solid to an external stimulus. This paper revisits and extends the microscopic formalism for calculating response coefficients – here referred to as (generalized) polarizabilities – in crystalline electronic
insulators. The main focus is on the Berry phase polarization and orbital magnetization, for which we obtain general formulas describing the linear response to an arbitrary (but static and uniform) perturbation. The response of an arbitrary
lattice-periodic observable (e.g.
spin, layer pseudospin) to electric and
magnetic fields is also examined, and serves as a basis for mircoscopically establishing Maxwell relations between conjugate generalized polarizabilities. We furthermore introduce and examine the notion of Berry
curvature or
Hall vector polarizability, i.e., the response of the Berry
curvature to a general perturbation, and show how it relates to Berry phase polarization and orbital magnetization responses. For all polarizabilities considered, we obtain simplified formulas applicable to two- and four-band models, expressed directly in terms of the
Hamiltonian and the perturbation. Three specific applications of these formulas are discussed: (i) a computation of the magnetoelectric polarizabilities of model antiferromagnets in one and two dimensions; (ii) a general proof of (quasi)topological signatures in the polarizabilities of Dirac
fermions in two dimensions; (iii) a calculation of the strain-induced Berry
curvature polarizability in an altermagnet.
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Disordered Systems and Neural Networks
Reentrant Localization Length in a Quasiperiodic Thue-Morse Chain
Taylan Yildiz and B. Tanatar
We investigate single-particle localization in a dimerized Su-Schrieffer-Heeger chain whose quasiperiodic onsite potential is masked by the deterministic Thue–Morse sequence. The behavior is characterized by the transfer-matrix Lyapunov exponent, and by the participation moments of exactly diagonalized chains. For intracell-dominated hopping the mid-spectrum Lyapunov exponent depends nonmonotonically on the potential strength, developing a pronounced minimum that enhances the localization length by an order of magnitude over an intermediate window, whereas an intercell-dominated chain responds monotonically. The exponent remains positive at every sampled nonzero potential strength and at every state of the spectral sector, and the second participation moment saturates over the full range of system sizes, so the intermediate window is an enhancement of a finite localization length and not a change of localization class. Finite-size generalized dimensions follow the same response in real space and in the Fourier-conjugate representation, while their moment-order separation decreases systematically with size. Controlled sign masks identify the origin: the response requires short-range sign anticorrelation aligned with the dominant bonds, and displacing the modulation by a single site, which destroys the exactness of that anticorrelation while leaving the sequence otherwise intact, removes the response entirely. An effective-dimer description relates the alignment to the division of the onsite modulation between the internal detuning of a bonded pair and its common-mode energy.
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Strongly Correlated Electrons · Cross-listed from hep-th
Near-extremal hydrodynamics and the holographic product formula
Edwan Préau
The
holographic product formula is used to determine the general form taken by
holographic spectral functions in the near-extremal hydrodynamic regime, with energy $\omega$, momentum $k$ and temperature $T$ much smaller than a hard scale $\mu$. The resulting expressions simplify in the extremal limit $T \ll \omega,k\ll \mu$, for which the low-temperature gapless modes and the IR conformal behavior factorize. In some cases, this factorization extends to the general near-extremal regime $\omega,k,T\ll\mu$ at leading order in $T/\mu$. Several examples are discussed with different types of gapless modes and IR CFTs, including new numerical results for low temperature quasi-normal modes. We end with a concrete application that shows how the inclusion of the IR conformal behavior improves the description of the spectral function at low energies.
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Statistical Mechanics
Collective dynamics of higher-order Vicsek model emerging from local conformity interactions
Iván León, Riccardo Muolo, Hiroya Nakao et al. (+1 more)
The Vicsek model is the paradigmatic framework for collective motion in systems of self-propelled particles. In its continuous-time formulation and most of its extensions,
alignment arises from pairwise interactions among neighboring particles. In this work, we consider a model in which each particle assigns weights to its neighbors according to their
alignment with the local consensus. This simple mechanism naturally yields a Vicsek-type model with pairwise and higher-order (i.e., nonpairwise) interactions. We analyze its collective dynamics through numerical simulations and approximate theory in the absence and presence of noise. The higher-order interactions generate a novel bidirectionally ordered phase, in which particles self-organize into oppositely moving groups. Moreover, we show that, depending on the relative strength of the pairwise and three-body interactions, the order-disorder transition can be either continuous or abrupt.
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All authors Iván León, Riccardo Muolo, Hiroya Nakao, Keisuke Taga
Strongly Correlated Electrons
Quantum Altermagnetic Instability in Disordered Metals
Alberto Cortijo
The possibility of a zero temperature, altermagnetic instability in anisotropic two dimensional electron systems in the diffusive regime is analyzed, in the presence and absence of
spin-orbit coupling. Allowing for ferromagnetism, a phase diagram is built as a function of the parameter that controls anisotropy and the strength of the interactions. It is found that, at zero
spin orbit coupling, ferromagnetism only dominates at small values of anisotropy and coupling constant. Larger values of these parameters favour the formation of altermagnetism. At finite
spin-orbit coupling, a paramagnetic phase competes with the other two, and a
quantum critical point appears. The phase transition from the paramagnetic to the magnetically ordered phases is of second order, while the phase transition between ferromagnet and altermagnet states is first order. The altermagnetic phase is robust under small
magnetic fields, displaying a coexistence with a field-induced magnetization.
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Soft Condensed Matter
Ashley Z. Guo, Sam Wilken, Dov Levine et al. (+1 more)
We investigate a 2D dynamical absorbing state model of monodisperse disks, in which rich phase behavior arises from interactions consisting solely of repulsive displacements between overlapping particles. The phase diagram reveals several unconventional features, including a disordered and static absorbing configuration, where no particles overlap, separated by a second-order phase transition to a continuously evolving active hexagonal
crystal with collective ring
diffusion, which in turn undergoes a first-order phase transition to an active isotropic
liquid. The only driving parameter is $\epsilon$, the maximum size of the random repulsive kicks. Small $\epsilon$ facilitates self-organization into an ordered state, but large $\epsilon$ prevents this organization from occurring. This is very different from typical order-disorder transitions, where there are two competing influences, energy and
entropy, that drive the transition.
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All authors Ashley Z. Guo, Sam Wilken, Dov Levine, Paul M. Chaikin
Soft Condensed Matter
CO2-induced Rejuvenation in Polyetherimide: a New Key to Understand the Brittle-to-Ductile Transition in Mechanical Behavior of Nanocellular Polymers
Felix Lizalde-Arroyo, Frederik Van Loock, Victoria Bernardo et al. (+2 more)
Nanocellular polyetherimide exhibits significant improvements in mechanical properties like toughness and impact resistance, commonly associated with the presence of nanoporosity. However, this work demonstrates these enhancements, often measured directly after processing, cannot be fully explained solely by the cellular structure but also originate from a modification of the
polymer matrix induced by the CO2-saturation process. Through a systematic study involving thermal treatments and saturation-desorption processes without foaming, it is shown that CO2 exposure, even in the absence of pore formation, induces an apparent rejuvenation of the
polymer, as evidenced by a reduction in the yield stress, which persists after complete CO2 desorption and in the absence of residual gas during mechanical testing. Therefore, the observed ductile response is not associated with the presence of CO2 during deformation, but with a permanent modification of the
polymer matrix induced by prior gas exposure. This structural state can be thermally reversed by activating the beta relaxation of the
polymer. For nanocellular
polymers, the presence of residual gas within the
matrix during foaming restricts thermal relaxation and helps preserve the CO2-modified state. As a result, the mechanical response of the solid phase reflects the intrinsic properties of the saturated
polymer and the architecture imposed by the cellular structure. This work demonstrates for the first time that CO2 saturation can permanently alter the mechanical state of a high-Tg amorphous
polymer, providing a new framework to interpret the brittle-to-ductile transition in nanocellular PEI.
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All authors Felix Lizalde-Arroyo, Frederik Van Loock, Victoria Bernardo, Miguel Angel Rodriguez-Perez, Judith Martin-de Leon
Mesoscale and Nanoscale Physics
Zero-field deterministic all-optical writing and annihilation of nanometer-scale skyrmion bubbles
M.G. van der Schans, W.P.M. de Kleijne, M.A. Brozius et al. (+1 more)
Skyrmions are highly stable
chiral magnetic spin textures with non-trivial
topology. They can act as quasi-particles that can be generated, manipulated and annihilated, and hold promise for future
memory and logic devices. As of now, all-optical
stochastic nucleation of skyrmion ensembles, mostly in small applied
magnetic fields, has been shown. However, to research their true potential, the ability to selectively toggle switch individual single skyrmions would be highly beneficial. In this paper, we demonstrate the field-free optical control of single stable skyrmions via single femtosecond
laser pulses with diameters down to 175 nm, containing a fixed chirality. By engineering ferrimagnetic Co/Gd-based multilayers, we resolve the competition between deterministic and
stochastic processes, and thereby overcome the challenge of optically writing and annihilating sub-micron skyrmions on demand. Our work is envisioned to fuel applications of skyrmion-based applications and opens up further endeavors in research related to the behaviour of more complicated skyrmion-based textures.
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All authors M.G. van der Schans, W.P.M. de Kleijne, M.A. Brozius, B. Koopmans
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Optical parametric free-electron–photon quantum interaction
Zetao Xie, Zehai Pang and Yi Yang
Optical parametric processes underpin
quantum photonics, while free-electron–
photon interactions offer agile pathways to generate nontrivial
quantum photonic states. These threads have so far largely progressed independently, whereas placing free electrons in a driven nonlinear system can potentially activate coherent parametric interaction channels for joint state engineering of both types of particles. Here we unify these paradigms by developing a general theoretical framework for parametric free-electron–
photon interactions in a nonlinear optical system driven by degenerate parametric down-conversion. Unlike free electrons in a linear bath, here they can couple to Bogoliubov quasiparticles through two detuned phase-matching channels, where the parametric process and free-electron interactions can
quantum amplify each other. Seeding the interaction with squeezed
vacuum yields gain-only or loss-only electron energy spectra, and enables electron-heralded squeezed Fock states; with bare
vacuum, postselecting electron energy sidebands generates high-fidelity Schrödinger cat states. Our results show how optical parametric interactions can
quantum shape free electrons and
photons, potentially enabling a
quantum parametric dielectric
laser accelerator that mitigates the need for temporal phase synchronization, thereby allowing acceleration probabilities to approach unity even for phase-random electrons.
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Soft Condensed Matter
Hierarchical and ultrametric barriers in the energy landscape of jammed granular matter
Shuonan Wu, Yuchen Xie, Deng Pan et al. (+2 more)
According to the mean-field glass theory, the (free) energy landscape of disordered systems is hierarchical and ultrametric if they belong to the full-replica-
symmetry-breaking universality class. However, examining this theoretical picture in three-dimensional systems remains challenging, where the energy barriers become finite. Here, we numerically explore the energy landscape of granular models near the jamming transition using a saddle dynamics
algorithm to locate both local energy minima and saddles. The multi-scale distances and energy barriers between minima are characterized by two metrics, both of which exhibit signatures of an ultrametric space. The scale-free distribution of energy barriers reveals that the landscape is hierarchical.
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All authors Shuonan Wu, Yuchen Xie, Deng Pan, Lei Zhang, Yuliang Jin
Disordered Systems and Neural Networks
Localization and persistent currents in a quasiperiodic disordered helical lattice
Taylan Yildiz and B. Tanatar
We investigate localization and persistent currents in a helical tight-binding
lattice subject to two independent
magnetic fluxes and a quasiperiodic on-site potential. Working with non-interacting, spinless
fermions under periodic boundary conditions, we solve the model by exact diagonalization and study localization with both inverse and normalized participation ratios. We identify boundaries separating extended, mixed, and localized regimes by constructing a diagram incorporating potential strength and inter-ring coupling. In the metallic regime, persistent currents flowing around both the toroidal and poloidal directions show oscillations whose amplitude decays as disorder grows and vanishes past the localization threshold; in the localized regime, currents become flux-insensitive. We demonstrate that tuning
magnetic fluxes, hopping strengths, or quasiperiodic potential amplitudes provides control over the critical disorder threshold. Our results suggest a versatile platform for disorder-and flux-controlled switching between conductive and insulating states.
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Disordered Systems and Neural Networks
Localization Properties of a Disordered Helical Chain
Taylan Yildiz and B. Tanatar
We study the localization properties of the quasiperiodic one-dimensional helical chain with two tunneling paths: nearest-neighbor and a long-range hop that connects sites of consecutive helical turns. Using exact diagonalization, we quantify localization employing the inverse participation ratio (IPR) and the normalized participation ratio (NPR), and combine them into a single measure to create a phase map. The resulting diagrams reveal three regimes: a completely extended phase, a completely localized phase, and a mixed domain where localized and extended states coexist. In the diagrams, we investigate the behaviors of tightly and loosely wound helices and examine a special case where the number of sites per turn is a Fibonacci number. For moderate numbers of sites per helical turn, the mixed region is broad and also shifts with the long-range coupling. When the turn size is a Fibonacci number, the phase boundary becomes nearly horizontal and the mixed region fades out, effectively recovering the standard Aubry-André model behavior.
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Strongly Correlated Electrons
Quantum decay of magnons in the unfrustrated honeycomb Heisenberg model
Calvin Krämer, Dag-Björn Hering, Vanessa Sulaiman et al. (+3 more)
We investigate the physical properties of elementary
magnon excitations of the ordered
antiferromagnetic Heisenberg model on the honeycomb
lattice using
quantum Monte Carlo (QMC) simulations, series expansions (SE), and continuous similarity transformations (CST). The
stochastic analytic continuation method is used to determine the dynamic structure factor from correlation functions in imaginary time obtained by QMC. In contrast to the "roton minimum" of the square
lattice Heisenberg antiferromagnet, we find that
magnons on the honeycomb
lattice completely decay in the corner of the Brillouin zone ($K$-point); the entire weight is shifted into the continuum. These findings are fully supported by SE and CST in momentum space. The extrapolated one-
magnon dispersion obtained from SE about the Ising limit quantitatively agrees with the extracted QMC excitation energies except around the $K$-point, where large uncertainties in the extrapolation indicate the
magnon decay. This
quantum decay is further confirmed and understood by the CST, which yields a divergent flow when enforcing a
magnon quasi-particle picture. The divergence originates from strong attractive
magnon-
magnon interactions leading to a bound state and thereby to a three-
magnon continuum overlapping with the one-
magnon state. This has the
magnon quasi-particle picture break down at high energies on the honeycomb
lattice.
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All authors Calvin Krämer, Dag-Björn Hering, Vanessa Sulaiman, Matthias R. Walther, Götz S. Uhrig, Kai Phillip Schmidt
Soft Condensed Matter
A Smoluchowski equation for a sheared suspension of frictionally interacting rods
Genevieve Quiñones and Peter D. Olmsted
In this work we develop constitutive equations for a dense, sheared suspension of frictionally interacting rods by applying Onsager's variational method as formulated by Doi. We treat both solid friction, of the Amontons-Coulomb form; and lubricated friction, which scales with relative tangential velocity at the contact point. Dissipation functions in terms of the rod angular velocity are derived via a mean field approach for each form of friction, and from these, a Rayleighian for dense suspensions of rigid rods under shear constructed. Derivatives of this Rayleighian with respect to rod angular velocity and velocity gradient give a Smoluchowski equation and stress tensor, respectively. We show that these are representable as perturbations to Doi's model for a sheared
liquid crystal. We also suggest a form for the average number of contacts between rods as a function of volume fraction, aspect ratio, and nematic order parameter, generalizing Philipse's random contact equation for disordered packings.
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Quantum Gases
Asymmetric and chiral dynamics of two-component anyons with synthetic gauge flux
Rui-Jie Chen, Ying-Xin Huang, Guo-Qing Zhang et al. (+1 more)
In this work, we investigate the non-
equilibrium dynamics in a one-dimensional two-component anyon-Hubbard model, which can be mapped to an extended Bose-Hubbard ladder with density-dependent hopping phase and synthetic gauge flux. Through numerical simulations of two-particle dynamics and the
symmetry analysis, we reveal the asymmetric transport with broken inversion
symmetry and two dynamical
symmetries in the expansion dynamics. The expansion of two-component anyons is dynamically symmetric under spatial inversion and component flip, when the sign of anyonic statistics phase or the signs of gauge flux and interaction are changed. In the non-interacting case, we show the dynamical suppression induced by both the statistics phase and gauge flux. In the interacting case, we demonstrate that both
chiral and antichiral dynamics can be exhibited and tuned by the statistics phase and gauge flux. The dynamical phase regimes with respect to the
chiral-antichiral dynamics are obtained. These findings highlight the rich dynamical phenomena arising from the interplay of anyonic exchange statistics, synthetic gauge fields, and interactions in multi-component anyons.
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All authors Rui-Jie Chen, Ying-Xin Huang, Guo-Qing Zhang, Dan-Wei Zhang
Materials Science
Brittle-to-ductile transition and strain relaxation in Si$_{1-x}$Ge$_x$ linearly graded buffers
Riccardo Civiero, Elena Campagna, Afonso Cerdeira Oliveira et al. (+5 more)
The strain-relaxation mechanism of a set of Si$_{0.6}$Ge$_{0.4}$ linearly graded buffers (LGBs), grown following different temperature profiles, has been investigated by means of defect-etching and variable-temperature high-resolution X-ray diffraction (VT-HRXRD). Defect-etching experiments demonstrate that a sharp increase of threading dislocation density (TDD) from $3 \times 10^{5}$\,cm$^{-2}$ to $1.2 \times 10^{6}$\,cm$^{-2}$ takes place when the final growth temperature exceeds a critical value T$_c\approx 530^\circ$C. VT-HRXRD measurements show that in low TDD samples extra relaxation takes place for annealing temperatures larger than T$_c$, thanks to the nucleation of new dislocations. These results indicate that, below T$_c$, strain relaxation is driven by the gliding of existing dislocations while above T$_c$ new dislocations are nucleated, suggesting a link with our results and the brittle-to-ductile transition in Si$_{1-x}$Ge$_x$
alloys.
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All authors Riccardo Civiero, Elena Campagna, Afonso Cerdeira Oliveira, Marvin Hartwig Zoellner, Davide Impelluso, Daniel Chrastina, Giovanni Capellini, Giovanni Isella
Strongly Correlated Electrons
Field-induced anomaly in the anisotropic non-Fermi-liquid normal state of UBe$_{13}$
Yusei Shimizu, Shunichiro Kittaka, Yohei Kono et al. (+6 more)
We report the results of high-resolution dc magnetization and specific-heat measurements at very low temperatures for a single
crystal \color{black} of UBe$_{13}$ in
magnetic fields applied along the [001] and [111] directions, in both the normal and superconducting states. In the normal state,
magnetic susceptibility $\chi(T) = M/H$ exhibits a logarithmic temperature dependence over a wide temperature range (1-20 K). However, with increasing field, this non-
Fermi-
liquid (NFL) behavior of $\chi(T) $ at low temperatures is suppressed. Moreover, a susceptibility maximum occurs below 4 T, whereas
Fermi-
liquid coherence is recovered above 8 T. In addition, thermodynamic anomalies ($T_{\rm A}$ and $H_{\rm A}$) occur in both
magnetic susceptibility and specific heat at intermediate fields (6–10 T) along the [111] direction. Furthermore, a nontrivial fifth-order nonlinear susceptibility is observed in the normal-state magnetization of UBe$_{13}$. These results suggest a close relationship between the field-induced multipolar correlations of $5f$-electron degrees of freedom and the
Fermi-surface reconstruction accompanying the crossover from the NFL state to the
Fermi-
liquid state in UBe$_{13}$.
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All authors Yusei Shimizu, Shunichiro Kittaka, Yohei Kono, Shota Nakamura, Yoshinori Haga, Etsuji Yamamoto, Kazushige Machida, Hiroshi Amitsuka, Toshiro Sakakibara
Mesoscale and Nanoscale Physics
Signature of inverse orbital Hall effect in silicon studied using time-resolved terahertz polarimetry
Ami Mi Shirai, Kota Aikyo, Yuta Murotani et al. (+6 more)
We investigated the anomalous
Hall conductivity induced in silicon by circularly polarized light at room temperature using near-infrared (NIR) pump-terahertz (THz) probe spectroscopy. The time-resolved detection scheme eliminates the large nonlinear current generated by the field-induced circular photogalvanic effect, allowing exclusive observation of a long-lived anomalous
Hall conductivity of photocarriers that depends on the helicity of NIR light. The magnitude of this conductivity is comparable to that of GaAs despite silicon's much weaker
spin-orbit coupling, and its robustness against NIR
photon energy rules out a
spin-polarization-based origin, which occurs only in the vicinity of the bandgap. These results suggest the emergence of the inverse orbital
Hall effect, paving the way for silicon-based orbitronics.
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All authors Ami Mi Shirai, Kota Aikyo, Yuta Murotani, Tomohiro Fujimoto, Changsu Kim, Hidefumi Akiyama, Shinji Miwa, Jun Yoshinobu, Ryusuke Matsunaga
Materials Science · Cross-listed from physics.med-ph
Enhanced Vascularity in Gelatin Scaffolds via Copper-Doped Magnesium-Calcium Silicates Incorporation: In-Vitro and Ex-Ovo Insights
Erfan Salahinejad, Avaneesh Muralidharan, Forough Azam Sayahpour et al. (+4 more)
Addressing a critical challenge in current tissue-engineering practices, this study aims to enhance vascularization in 3D porous scaffolds by incorporating bioceramics laden with pro-angiogenic ions. Specifically, freeze-dried gelatin-based scaffolds were infused with sol-gel-derived powders of Cu-doped akermanite (Ca2MgSi2O7) and bredigite (Ca7MgSi4O16) at various concentrations (10, 20, and 30 wt%). The scaffolds were initially characterized for their structural integrity, biodegradability, swelling behavior, impact on physiological pH, and cytocompatibility with human umbilical vein endothelial
cells (HUVECs). The silicate incorporation effectiveness in promoting vascularity was then assessed through HUVEC attachment, capillary tube formation, and ex-ovo chick embryo chorioallantoic membrane assays. The findings revealed significant improvements in both in-vitro and ex-ovo vascularity of the gelatin scaffolds upon the addition of Cu-doped akermanite. The most effective concentrations were determined to be 10 and 20%, which led to notable HUVEC metabolic activity, a well-spread morphology with extensive peripheral filopodia and lamellipodia at 10% and a cobblestone phenotype indicative of in-vivo endothelium at 20% during
cell attachment, the formation of complex networks of tubular structures, and robust vascularization in chick embryo development. Moving forward, the incorporation of Cu-doped akermanite into tissue-engineering scaffolds shows great potential for addressing the limitations of vascularization, especially for critical-sized bone defects, by facilitating the controlled release of pro-angiogenic and pro-osteogenic ions.
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All authors Erfan Salahinejad, Avaneesh Muralidharan, Forough Azam Sayahpour, Maryam Kianpour, Mohsen Akbarian, Daryoosh Vashaee, Lobat Tayebi
Superconductivity
Gate-imprinted memory and light-induced erasure of superconductivity at KTaO$_3$-based interfaces
Zhihao Chen, Pengxu Ran, Ming Dong Dong et al. (+7 more)
Realizing non-volatile control of superconductivity is a key step toward integrating
memory and
quantum functionality in future information technologies. KTaO$_3$-based
heterostructures uniquely host interfacial two-dimensional superconductivity and
quantum paraelectric
lattice background. The coupling between these two degrees of freedom potentially provides a promising route to encode
memory into the superconducting state. Here we reveal two intertwined phenomena in AlO$_x$/KTaO$_3$
heterostructures: a gate-imprinted
memory in which electrostatic gate cycling promotes superconductivity, and its erasure by optical illumination at cryogenic temperatures. These phenomena arise from a previously unrecognized interplay between the superconducting interface and emergent
lattice excitations including polar-nanoregion reorientation and charge trapping/detrapping by oxygen vacancies. These results demonstrate configurable superconductivity at correlated
oxide interfaces, opening a pathway to enrich dissipationless transport with non-volatile controls for superconducting elements.
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All authors Zhihao Chen, Pengxu Ran, Ming Dong Dong, Jiexiong Sun, Fengmiao Li, Zhixin Yao, Lei Liu, Jie Wu, Juan Jiang, Zhi Gang Cheng
Superconductivity
Interfacial Polarons Driven by Charge Transfer In WSe2/Cuprate Superconductor Systems
Huimin Liu, Tong Yang, Xiongfang Liu et al. (+13 more)
Understanding the electronic properties of doped copper-oxygen planes remains a significant challenge in condensed matter physics and is crucial to unraveling the mechanisms behind high-temperature superconductivity in cuprates. Recently, the observation of charge transfer and interfacial polarons in superconducting interface has aroused extensive research interest. However, experimental data to investigate charge transfer on the CuO2 plane and the presence of polarons are still missing. Here we conduct extensive research on the optical and electronic properties of two-dimensional material supported on copper-based
superconductors. Unlike monolayer-WSe2 on other substrates, monolayer-WSe2 on La1.85Sr0.15CuO4 (WSe2/LSCO) produces a special band structure. Using high-resolution spectroscopic ellipsometry and density functional theory calculation methods, the special electronic structure can be attributed to the formation of the interfacial small polaron at the WSe2/LSCO interface which is driven by charge transfer between the CuO2 plane of the cuprate
superconductor and WSe2. In addition, the structural phase transition of the LSCO substrate was observed to reduce the electron-hole (e-h) interaction of WSe2. These findings may spur future investigations on the effect of the interfacial polaron on the superconductivity of cuprates, and highlight the significant influence of interface effects on the electronic structure of WSe2 films. It provides an effective method to further explore the intrinsic relationship between interfacial polarons and superconductivity.
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All authors Huimin Liu, Tong Yang, Xiongfang Liu, Shengwei Zeng, Muhammad Fauzi Sahdan, Wenjun Wu, Shuo Sun, Tengyu Jin, Chuanbing Cai, Ariando Ariando, Mark B. H. Breese, Wenjing Zhang, Andrew T. S. Wee, Chi Sin Tang, Ming Yang, Xinmao Yin
Mesoscale and Nanoscale Physics
Enhanced superconducting diode effect in hybrid Josephson junctions
Peng Yu, Han Fu, William F. Schiela et al. (+7 more)
The superconducting diode effect (SDE) has recently been observed in various systems, sparking interest in novel superconducting devices and offering a new platform to probe intrinsic material properties. Josephson junctions with strong Rashba
spin-orbit coupling have exhibited nonreciprocal critical currents under applied
magnetic fields. In this work, we investigate the SDE in Josephson junctions incorporating periodic hole arrays patterned into the superconducting leads on InAs
heterostructures with epitaxial aluminum. We observe an enhanced diode effect when a top gate depletes the 2DEG in the region of the hole arrays, while preserving the overall supercurrent. Theoretical analysis shows that the physics behind this phenomenon is the increased difference of transparency between different bands in the junction. These results highlight a new pathway for engineering and controlling nonreciprocal superconducting transport in hybrid systems.
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All authors Peng Yu, Han Fu, William F. Schiela, William Strickland, Bassel Heiba Elfeky, S. M. Farzaneh, Jacob Issokson, Wei Pan, Enrico Rossi, Javad Shabani