Strongly Correlated Electrons
Microscopic Constructions of the $BF+AAB$ Topological Field Theory and Borromean-Rings Braiding in $(3+1)$ Dimensions
Yizhou Huang, Zhi-Feng Zhang, Qing-Rui Wang et al. (+1 more)
Topological order was first studied in fractional
quantum Hall states, where anyons reflect electron fractionalization. Recent advances in continuum topological field theories have revealed braiding, fusion, shrinking, and diagrammatic consistency relations in higher dimensions [e.g., Huang, Zhang, Ye, JHEP 11 (2023) 210; JHEP 06 (2025) 238]. As the next step of research, these advances call for explicit microscopic
lattice constructions that faithfully reproduce the structures and processes described by continuum field theories. Here we construct, step by step, microscopic counterparts of the $(3+1)$-dimensional $BF$ field theory with an $AAB$ twist and gauge group $(\mathbb{Z}_2)^3$. This field theory was introduced in our earlier work on Borromean-Rings braiding [Chan, Ye, Ryu, Phys. Rev. Lett. 121, 061601 (2018)]. We start with the construction of string and thickened membrane operators that create, fuse, shrink, and braid particle and loop excitations, providing microscopic counterparts of Wilson operators in continuum field theories. We derive fusion and shrinking rules and the operators governing particle–loop and Borromean-Rings braiding. We demonstrate selective control of non-Abelian shrinking channels through the internal degrees of freedom of loop operators and establish fusion–shrinking consistency for arbitrary finite groups. An explicit correspondence between all 22 excitations of the $\mathbb{D}_4$
quantum double
lattice model and the $BF+AAB$ theory preserves fusion and shrinking rules and particle–loop and Borromean-Rings braiding phases. These constructions place the continuum results on a microscopic
lattice footing with tensor-product local
Hilbert spaces and short-range interactions.
Read the full abstract ▾
All authors Yizhou Huang, Zhi-Feng Zhang, Qing-Rui Wang, Peng Ye
Materials Science · Cross-listed from quant-ph
Thermodynamic sampling of materials using neutral-atom quantum computers
Bruno Camino, Mao Lin, John Buckeridge et al. (+1 more)
Neutral-atom
quantum hardware has emerged as a promising platform for programmable many-body physics. In this work, we develop and validate a practical framework for extracting thermodynamic properties of materials using such hardware. As a test case, we consider nitrogen-doped
graphene. Starting from Density Functional Theory (DFT) formation energies, we map the material energetics onto a Rydberg-atom
Hamiltonian suitable for
quantum annealing by fitting an on-site term and distance-dependent pair interactions. The
Hamiltonian derived from DFT cannot be implemented directly on current QuEra devices, as the largest energy scale accessible on the hardware is two orders of magnitude smaller than the target two-body interaction in the material. To overcome this limitation, we introduce a rescaling strategy based on a single parameter, $\alpha_v$, which ensures that the distribution sampled by the hardware is well described by Boltzmann-like weights corresponding to those of the material at an effective temperature $T^{\prime} = \alpha_v T$, where $T$ is the device sampling temperature. This rescaling also establishes a direct correspondence between the global
laser detuning $\Delta_g$ and the grand-canonical chemical potential $\Delta\mu$. We validate the method on a 28-site
graphene nanoflake using exhaustive enumeration, and on a larger 78-site system where Monte Carlo sampling confirms preferential sampling of low-energy configurations.
Read the full abstract ▾
All authors Bruno Camino, Mao Lin, John Buckeridge, Scott M. Woodley
Materials Science · Cross-listed from quant-ph
Photoexcitation of moiré-trapped interlayer excitons via chiral phonons
A. Borel, T. V. Ivanova, J. Cervantes-Villanueva et al. (+7 more)
Moiré superlattices in transition-metal dichalcogenide
semiconductor heterobilayers enable the
quantum confinement of interlayer
excitons with large out-of-plane permanent electric dipoles and
spin-valley control. Here, we report a novel
phonon-assisted excitation mechanism of individual moiré-trapped interlayer
excitons in 2H-stacked MoSe$_2$/WSe$_2$ heterobilayers via
chiral $E^{\prime\prime}$ in-plane optical
phonons at the {\Gamma}-point. This excitation pathway preserves valley-selective optical selection rules and enables deterministic generation of individual interlayer
excitons with defined helicity, emitting within a spectrally narrow energy spread. Through photoluminescence excitation spectroscopy in both the ensemble and
quantum emitter regimes, we identify a fixed
phonon energy of $\sim$23 meV mediating the process. First-principles calculations corroborate the
symmetry and energy of the relevant
phonon mode and its coupling to interlayer
excitons, providing microscopic support for the observed valley-selective
phonon-assisted excitation mechanism. Our results highlight the utility of
chiral phonons as a tool for controlled excitation of
quantum emitters in TMD moiré systems, opening new opportunities for valleytronic and
quantum photonic applications.
Read the full abstract ▾
All authors A. Borel, T. V. Ivanova, J. Cervantes-Villanueva, P. Thor, H. Baek, T. Taniguchi, K. Watanabe, A. Molina-Sanchez, B. D. Gerardot, M. Brotons-Gisbert
Mesoscale and Nanoscale Physics
Topological Interface States and Nonlinear Thermoelectric Performance in Armchair Graphene Nanoribbon Heterostructures
David M T Kuo
We investigate the emergence and topological nature of interface states (IFs) in N-AGNR/$(N-2)$-AGNR/N-AGNR
heterostructure (AGNRH) segments lacking translational
symmetry, focusing on their relation to the end states (ESs) of the constituent armchair
graphene nanoribbon (AGNR) segments. For AGNRs with $R_1$-type unit
cells, the ES numbers under a longitudinal electric field follow the relations $N = N_{A(B)} \times 6 + 1$ and $N = N_{A(B)} \times 6 + 3$, whereas $R_2$-type unit
cells exhibit $(N_{A(B)} + 1)$ ESs. The subscripts $A$ and $B$ denote the chirality types of the ESs. The Stark effect lifts ES degeneracy and enables clear spectral separation between ESs and IFs. Using a real-space bulk boundary perturbation approach, we show that opposite-chirality states hybridize through junction-site perturbations and may shift out of the bulk gap. The number and chirality of IFs in symmetric AGNRHs are determined by the difference between the ESs of the outer and central segments, $N_O$ and $N_C$, according to $N_{IF,\beta} = |N_{O,B(A)} - N_{C,A(B)}|$, where $\beta$ labels the chirality. Depending on whether $N_O > N_C$ or $N_C > N_O$, the resulting IFs acquire B- or A-chirality, respectively. Calculated transmission spectra ${\cal T}_{GNR}(\varepsilon)$ reveal that AGNRHs host a topological double
quantum dot (TDQD) when IFs originate from the ESs of the central AGNR segment. Using an Anderson model with effective intra-dot and inter-dot Coulomb interactions, we derive an analytical expression for the tunneling current through the TDQD via a closed-form transmission coefficient. Thermoelectric analysis shows that TDQDs yield enhanced nonlinear power output in the electron-dilute and hole-dilute charge states, with Coulomb blockade suppressing thermal current but not thermal voltage.
Read the full abstract ▾
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Holonomic multi-controlled gates for single-photon states
Carlo Danieli, Valentina Brosco, Claudio Conti et al. (+1 more)
Controlled and multi-controlled
quantum gates, whose action on a target
qubit depends on the state of multiple control
qubits, represent a fundamental logical building block for complex
quantum algorithms. We propose a scheme for realizing this class of gates based on non-Abelian holonomies in modulated photonic waveguide networks. Our approach relies on linear photonic cicuits formed by two
star networks coupled via a two-path
circuit. A
star network with M peripheral waveguides coupled to a single central site, or M-pod, naturally generalizes the tripod structure used in non-Abelian Thouless pumping and stimulated Raman adiabatic passage (STIRAP). In the present work, we first analyze the minimal case of two connected tripods and design adiabatic driving loops that implement single-
qubit, CNOT, and SWAP gates. We then show how extending the approach to larger M-pod structures enables the realization of multiply controlled operations, which we exemplify by designing Toffoli and the OR gate on two coupled pentapods. Finally, we demonstrate that networks of connected tripods can implement the Deutsch
quantum query
algorithm.
Read the full abstract ▾
All authors Carlo Danieli, Valentina Brosco, Claudio Conti, Laura Pilozzi
Materials Science
Ferromagnetic interface engineering of spin-charge conversion in RuO$_2$
Dongchao Yang, Zhaoqing Li, Yu Dai et al. (+4 more)
Spin-orbit torque efficiency is conventionally fixed by bulk materials. $D$-wave altermagnets introduce an additional nonrelativistic
spin-charge conversion channel beyond inverse
spin-
Hall effect. Using prototypical candidate RuO$_2$ as an example, we show that the adjacent ferromagnet alone can dictate both the magnitude and sign of
spin-charge conversion.
Spin-pumping measurements on RuO$_2$/Y$_3$Fe$_5$O$_{12}$ (YIG) and RuO$_2$/Ni$_{80}$Fe$_{20}$ (Py)
bilayers yield opposite effective
spin-
Hall angles that persist across crystalline and polycrystalline RuO$_2$. Inserting an ultrathin Au spacer at the RuO$_2$/YIG interface reverses the signal, envidencing a dominant interfacial inverse Rashba-Edelstein effect, whereas RuO$_2$/Py is governed by bulk inverse
spin-
Hall effect. First-principles calculations trace this dichotomy to interface-selective band hybridization: Rashba surface states survive at the insulating YIG contact yet are quenched by metallic Py. Our findings establish
ferromagnetic interfacing as a deterministic knob for tailoring
spin-charge conversion in altermagnetic
oxides, paving the way to field-free, low-dissipation spintronic
memory devices.
Read the full abstract ▾
All authors Dongchao Yang, Zhaoqing Li, Yu Dai, Lili Lang, Zhong Shi, Zhe Yuan, Shi-Ming Zhou
Strongly Correlated Electrons
Optical Detection and Manipulation of Pseudospin Orders in Wigner Crystals
Yichen Dong, Eugene Demler and Zhiyuan Sun
In Wigner-
crystal states of two-dimensional electrons, the
spin ordering remains poorly understood. The small energy differences between candidate
spin orders make theoretical studies less reliable, and probing
magnetic order at a nonzero wave vector is experimentally challenging. In modern realizations of Wigner
crystals, the electronic
spin degree of freedom is often replaced by a valley pseudospin associated with nonzero Berry
curvature. The resulting anomalous velocity couples the electrons' pseudospin texture to their orbital vibration. We show that this mechanism enables optical detection of pseudospin orders in Wigner
crystals by producing sharp signatures in the terahertz optical conductivity. For example,
antiferromagnetic pseudospin order enables light to excite collective electronic vibrations at the ordering wave vector, generating a characteristic absorption peak. Based on the same principle, we further show that a strong optical drive generates an effective potential that reshapes the pseudospin energy landscape, inducing phase transitions to stripe
antiferromagnetic states. These results point to a route for optical detection and control of
spin order via its coupling to orbital motion.
Read the full abstract ▾
Materials Science
Active Learning Guided Computational Discovery of 2D Materials with Large Spin Hall Conductivity
Abhijeet J. Kale, Sanjeev S. Navaratna, Pratik Sahu et al. (+3 more)
Two-dimensional (2D) materials are promising candidates for next-generation spintronic devices due to their tunable properties and potential for efficient
spin-charge interconversion. However, discovering materials with intrinsically high
spin Hall conductivity (SHC) is hindered by the vast chemical space and expensive nature of conventional experimental and first-principles methods. In this work, we employ an active learning framework to accelerate the discovery of high-SHC 2D materials. Machine learning (ML) models were trained on SHC values computed from density functional theory calculations, incorporating the Kubo formalism via tight-binding
Hamiltonians constructed from maximally localized Wannier functions, with explicit treatment of
spin-orbit coupling. Starting from random but chemically diverse 24 2D systems, the
dataset was expanded to 41 cases (from an overall pool of around 2000 materials) over three active learning loops using an expected improvement acquisition strategy. The ML technique successfully identified several high SHC candidates with the best candidate exhibiting a SHC of 271.52 (hbar/e) Ohm^-1, nearly 23 times higher than the top performer in the initial round. Beyond candidate discovery, several features such as orbital
symmetry near the
Fermi energy, types of atomic species, material composition, covalent radii, and electronegativity of constituent atoms were found to play critical role in shaping the
spin Hall response in 2D systems. The data generated is made publicly available to facilitate further advances in 2D spintronics.
Read the full abstract ▾
All authors Abhijeet J. Kale, Sanjeev S. Navaratna, Pratik Sahu, Henry Chan, B. R. K. Nanda, Rohit Batra
Strongly Correlated Electrons
Hysteretic Phonons and Quasielastic Response: A Raman Study of Thermal Memory in Two-dimensional CuCrP2S6
Chaitanya B. Auti, Atul G. Chakkar, Sebastian Selter et al. (+4 more)
We present a comprehensive temperature and polarization dependent inelastic light scattering (Raman) study on single
crystals of two-dimensional CuCrP2S6, a layered van der Waals material exhibiting coupled
magnetic and electric degrees of freedom. Raman measurements were performed from 5 to 300 K to probe
phonon dynamics across multiple structural and
magnetic phase transitions. Our analysis reveals pronounced thermal hysteresis in
phonon self-energy parameters and dynamic Raman susceptibility, confirming the first-order nature of the antipolar transition near TC1 ~ 145 K and a second-order transition near TC2 ~ 190 K. Low-frequency modes associated with Cu+ and Cr3+ ions exhibit softening and anomalous linewidth behaviour, in particular
phonon mode P2 (~ 37 cm-1) showing non-monotonic temperature dependence and intensity enhancement near 60 K suggesting persistent off-centre Cu+ dynamics in the quasi-antipolar phase. The coexistence and coupling of soft
phonon modes and central peaks indicate a crossover from displacive to order-disorder type transition mechanisms. Additionally,
phonon anomalies below the Néel temperature (TN ~ 32 K) reflect
spin-
phonon coupling, linking
lattice vibrations to long-range
magnetic correlations. Our findings provide critical insight into the
lattice instabilities,
symmetry evolution, and quasiparticle interactions in CuCrP2S6, offering a deeper understanding of phase transition dynamics in two-dimensional multiferroic systems and guiding future design of magnetoelectric and spintronic devices.
Read the full abstract ▾
All authors Chaitanya B. Auti, Atul G. Chakkar, Sebastian Selter, Yuliia Shemerliuk, Bernd Büchner, Saicharan Aswartham, Pradeep Kumar
Materials Science
From cluster to nanocrystal: the continuous evolution and critical size of copper clusters revealed by machine learning
Hongsheng Liu, Luneng Zhao, Yaning Li et al. (+5 more)
The
evolution of cluster structure with size and the critical size for the transition from cluster to nanocrystal have long been fundamental problems in nanoscience. Due to limitations of experimental technology and computational methods, the exploration of the continuous
evolution of clusters towards nanocrystal is still a big challenge. Here, we proposed a machine learning force field (MLFF) that can generalize well to various copper systems ranging from small clusters to large clusters and bulk. The continuous
evolution of copper clusters CuN towards nanocrystal was revealed by investigating clusters in a wide size range (7 <= N <= 17885) based on MLFF simulated annealing. For small CuN (N < 40), electron counting rule plays a major role in stability. For large CuN (N > 80),
geometric magic number rule plays a dominant role and the
evolution of clusters is based on the formation of more and more icosahedral shells. For medium size CuN (40 <= N <= 80), both rules contribute. The critical size from cluster to nanocrystal was calculated to be around 8000 atoms (about 6 nm in diameter). Our work terminates the long-term challenge in nanoscience, and lay the methodological foundation for subsequent research on other cluster systems.
Read the full abstract ▾
All authors Hongsheng Liu, Luneng Zhao, Yaning Li, Yuan Chang, Shi Qiu, Xiao Wang, Junfeng Gao, Feng Ding
Statistical Mechanics
Collective behavior of independent scaled Brownian particles with renewal resetting
Ohad Vilk and Baruch Meerson
We study fluctuations of an ensemble of $N$ independent particles undergoing anomalous
diffusion with random renewal resetting. The anomalous
diffusion is modeled by the scaled Brownian motion (sBm): a Gaussian process, characterized by a power-law time dependence of the
diffusion coefficient, $D(t)\sim t^{2H-1}$, where $H>0$. The particles independently reset to the origin, and each particle's clock is set to zero upon spatial resetting. Employing the known steady-state position distribution of a single particle undergoing the sBm with renewal resetting [Bodrova et al., Phys. Rev. E 100, 012120 (2019)], we study the statistics of the system radius $\ell$ and of the center of mass (COM) of $N\gg 1$ particles. Typical fluctuations of $\ell$ fall under the Gumbel universality class for all $H>0$, and we use extreme value statistics to calculate the moments of $\ell$. We show that, for $H>1/2$, large deviations of the COM exhibit an anomalous scaling behavior. We also uncover a singularity in the corresponding rate function at $N\to\infty$, which is caused by a “big jump" effect.
Read the full abstract ▾
Soft Condensed Matter
Wave-Like Statistics from Classical Active Particles with Internal Degrees Of Freedom
Rahil N. Valani
Wave-like spatial statistics in walking-droplet systems are often associated with wave-mediated interactions and wave-
memory effects. Here we explore how similar statistical structure can arise from the low-dimensional nonlinear dynamics of an inertial active particle with internal degrees of freedom. In this framework, steady propulsion corresponds to internal-state fixed points whose spiral or transiently chaotic relaxation organizes oscillatory ensemble densities. Local perturbations then generate wave-like statistics in both open and closed geometries, suggesting that wave-like ensemble behavior may emerge more generally from internal-state attractor dynamics in inertial active matter.
Read the full abstract ▾
Strongly Correlated Electrons · Cross-listed from hep-th
Black hole as a multipartite entangler: multi-entropy in AdS${}_3$/CFT${}_2$
Takanori Anegawa, Shota Suzuki and Kotaro Tamaoka
We study multipartite
entanglement in typical pure states holographically dual to pure BTZ black holes, using multi-
entropy and its “genuine” version. In the bulk, these quantities are computed by minimal geodesic networks (so-called Steiner trees). We find that at sufficiently high temperature, the genuine tripartite multi-
entropy exhibits a volume-law scaling in sharp contrast to
vacuum AdS$_3$, where the genuine contribution is universal and size-independent. Moreover, we find another phase: once one subsystem exceeds half of the total system, the leading genuine tripartite
entanglement vanishes and reduces to that for global AdS${}_3$. This transition is indeed consistent with recent arguments for distillable EPR pairs in tripartite Haar-random states. Motivated by finite-cutoff holography, we further study the radial cutoff dependence of multi-
entropy and show that genuine multi-
entropy acquires nontrivial size dependence even for the tripartite case in AdS${}_3$. As a byproduct, we also observe an intriguing “area-law” contribution to multi-
entropy that is relevant to
vacuum AdS${}_3$.
Read the full abstract ▾
Other Condensed Matter · Cross-listed from physics.optics
Complex Refractive Index Extraction for Spintronic Terahertz Emitter Analysis
Yingshu Yang, Keynesh Dongol, Stefano Dal Forno et al. (+7 more)
Spintronic terahertz emitters (STEs) generate broadband terahertz (THz) radiation, which is essential for spectroscopy, imaging, and communication. The performances and the essential physical parameters of STE devices are linked to the dielectric properties of the constituent materials. Terahertz time-domain spectroscopy (THz-TDS) is an effective tool to measure these properties, but conventional analysis struggles with thin or complex multilayered systems due to simplifying approximations or complex transfer functions. In this work, we present a practical method to extract dielectric properties of STE multilayers using the Transfer
Matrix Method (TMM). By comparing the THz pulse calculated using the Transfer
Matrix Method (TMM) with the experimentally measured pulse transmitted through the sample, we can extract the dielectric properties of STEs, enhancing THz-TDS analysis and facilitating STE design and optimization. This method avoids constructing complex transfer functions, accommodates diverse sample geometries, and is designed to be accessible, with a publicly available codebase, making it a useful tool for STE research.
Read the full abstract ▾
All authors Yingshu Yang, Keynesh Dongol, Stefano Dal Forno, Ziqi Li, Piyush Agarwal, Amalini Mansor, Ranjan Singh, Marco Battiato, Elbert E. M. Chia, Guoqing Chang
Materials Science
Realization of Insulating Buffer Layers via MOCVD-Grown Nitrogen-Doped (010) e̱ta}-Ga2O3
Rachel Kahler, Carl Peterson and Sriram Krishnamoorthy
We present MOCVD-grown, nitrogen-doped e̱ta}-Ga2O3 films as an insulating buffer layer on Fe-doped (010) e̱ta}-Ga2O3 substrates in lieu of 49% HF treatment to remove unintentional silicon at the substrate-epitaxial layer growth interface. N-doped layer thickness and NH3 flow were systematically varied to experimentally determine the lowest nitrogen concentration and thickness of the buffer layer needed to fully compensate the interfacial silicon peak. The NH3 molar flow rate was varied from 200 sccm to 1800 sccm. Results showed fully insulating N-doped layers for samples with NH3 flow rates greater than or equal to 1200 sccm and a thickness of 50 nm. This study demonstrates the efficacy of in-situ, controllably doped nitrogen buffer layers as a mitigation method for unintentional interfacial silicon at the substrate-epitaxial layer growth interface.
Read the full abstract ▾
Materials Science
Ab initio Approach to Collective Excitations in Excitonic Insulators
Fengyuan Xuan, Jiexi Song and Zhiyuan Sun
An ab initio approach is presented for studying the collective excitations in excitonic
insulators, charge/
spin density waves and
superconductors. We derive the Bethe-Salpeter-Equation for the particle-hole excitations in the quasiparticle representation, from which the collective excited states are solved and the corresponding order parameter fluctuations are computed. This method is demonstrated numerically for the excitonic insulating phases of the biased WSe2-MoSe2
bilayer. It reveals the gapless phase-mode, the subgap Bardasis-Schrieffer modes and the above-gap scattering states. Our work paves the way for quantitative predictions of excited state phenomena from first-principles calculations in electronic systems with spontaneous
symmetry breaking.
Read the full abstract ▾
Superconductivity
Evidence for Clean d-wave Superconductivity in Samarium Nickelates
Qingming Huang, Xiaofang Fu, Junlong Wu et al. (+3 more)
The discovery of superconducting nickelates provides a unique opportunity to explore the pairing mechanism of high-temperature superconductivity. Here, we use ultrafast terahertz spectroscopy to probe the temperature-dependent superfluid density in an infinite-layer samarium nickelate film with a Tc of 20 K. The superfluid density decreases linearly with rising temperature, consistent with clean limit d-wave pairing. From this linear relation, we extract a superconducting gap of 2.5 meV and a gap-to-Tc ratio of 3, suggesting that this sample lies in the weak-coupling limit. Furthermore, the ratio of the mean free path to the coherence length, is determined to be 1.5, confirming the clean-limit behavior. These findings establish strong parallels between the pairing mechanisms in nickelate and cuprate
superconductors.
Read the full abstract ▾
All authors Qingming Huang, Xiaofang Fu, Junlong Wu, Laifeng Li, Liang Qiao, Ye Yang
Materials Science
Deciphering the lattice vibrational behaviors of CuInP2S6 by angle-resolved polarized Raman scattering
Yiqi Hu, Jun-Jie Zhang, Zhou Zhou et al. (+12 more)
The layered van der Waals (vdW) ferroelectric CuInP2S6 (CIPS) exhibits unique cation hopping-driven phenomena that bring about unconventional properties with intriguing mechanisms and hold promises for advanced applications in nanoelectronics. However, an explicit analysis of its
lattice dynamics and vibrational
symmetries, pivotal for understanding the material's peculiar ferroelectric and ferroionic behaviors, remains incomplete. Here, we employ angle-resolved polarized Raman spectroscopy in concert with first-principles calculations to systematically unravel the anisotropic
lattice vibrations of CIPS single
crystals. By analyzing the polarization-dependent Raman intensities, we determine the
symmetry assignments and Raman tensors of all major vibrational modes, revealing good agreement with theoretical predictions. Furthermore, we demonstrate the utility of Raman spectroscopy as a sensitive and non-invasive probe for structural and ferroelectric order
evolution, by examining temperature-driven phase transitions and thickness-dependent polarization suppression in CIPS. Our findings establish a foundational framework for correlating
lattice dynamics with functional properties in CIPS and provide a methodological blueprint for studying other vdW ferroelectrics.
Read the full abstract ▾
All authors Yiqi Hu, Jun-Jie Zhang, Zhou Zhou, Shun Wang, Qiankun Li, Yanfei Hou, Tianhao Ying, Lingling Yang, Jingyao Zhang, Shuzhong Yin, Yuyan Weng, Shuai Dong, Jianlin Yao, Liang Fang, Lu You
Strongly Correlated Electrons
Competing magnetic and topological orders in the spin-1 Kitaev-Heisenberg chain with single-ion anisotropy
Sahinur Reja and Satoshi Nishimoto
We investigate the ground-state phase diagram of the
spin-1 Kitaev–Heisenberg chain in the presence of uniaxial single-ion anisotropy (SIA) $D_z$ by density-
matrix renormalization group (DMRG) calculations. By combining energy-
curvature diagnostics on periodic $N=24$ clusters with a refined characterization based on order parameters and correlation functions for open chains up to $N=144$, we establish a comprehensive phase diagram in the $\phi$–$D_z$ plane. We identify four magnetically ordered phases – FM-$z$, FM-$xy$, Néel-$z$, and a two-sublattice collinear LLRR2 state – as well as magnetically disordered/critical regimes including Néel-$xy$, LLRR1, and two Kitaev
spin-
liquid (KSL) regions. A topological Haldane phase also emerges near the Heisenberg limit. Our results provide evidence that both AFM- and FM-KSL regimes acquire finite parameter widths in the
spin-1 model, while the Haldane phase is fragile against Kitaev-type anisotropy, particularly for $D_z<0$. Increasing (decreasing) $D_z$ suppresses (enhances)
magnetic order and expands (shrinks) the KSL and other magnetically disordered sectors. Also, at $D_z=0$, we identify an exactly solvable point at $\phi=\tan^{-1}(-2)$, which enforces a first-order transition between Néel-$z$ and LLRR2. We further contrast these findings with the
spin-$1/2$ KH chain and with the
spin-1 honeycomb KH model, highlighting the distinct roles of dimensionality and SIA in Kitaev-type magnets.
Read the full abstract ▾
Materials Science
A voltage-responsive strongly dipolar-coupled macrospin network with emergent dynamics for computing
Xinglong Ye, Zhibo Zhao, Qian Wang et al. (+15 more)
Emergent behavior, which arises from local interactions between simple elements, is pervasive in nature. It underlies the energy-efficient computing in our
brains. However, realizing such dynamics in artificial materials, particularly under low-energy stimuli, remains a fundamental challenge. While dipole-dipole interactions are typically suppressed in
magnetic storage, here we harness and amplify them to construct a strongly dipolar-coupled network of SmCo5 macrospins at wafer scale, which can exhibit intrinsic interaction-driven collective dynamics in response to voltage pulses. The network combines three essential ingredients: strong dipolar coupling by large single-domain macrospin,
giant voltage control of coercivity over nearly 1000-fold, and disordered network
topology with frustrated Ising-like energy landscape. When stimulated by 1 V pulses, the network enters a regime where interaction-driven
magnetic behaviors emerge, including spontaneous demagnetization, greatly enhanced magnetization modulation, reversible freeze and resume
evolution and
stochastic convergence toward low-energy
magnetic configurations. All these behaviors are completely absent at the single-nanomagnet level. Furthermore, by constructing micromagnetic models of the strongly dipolar-coupled macrospin networks, we show that the resulting nonlinear, high-dimensional collective dynamics, intrinsic to strongly-interacting systems, can enable accurate chaotic Mackey-Glass prediction and multiclass drone-signal classification. Our work establishes the voltage-responsive strongly-coupled SmCo5 network as a mesoscopic platform for probing emergent
magnetic dynamics previously inaccessible under ambient conditions. It also suggests a fundamental distinct route towards scalable, low-voltage computing, one rooted in native physical interaction-driven collective dynamics at the network level.
Read the full abstract ▾
All authors Xinglong Ye, Zhibo Zhao, Qian Wang, Jiangnan Li, Fernando Maccari, Ning Lu, Christian Dietz, Esmaeil Adabifiroozjaei, Leopoldo Molina-Luna, Yufeng Tian, Lihui Bai, Guodong Wang, Konstantin Skokov, Yanxue Chen, Shishen Yan, Robert Kruk, Horst Hahn, Oliver Gutfleisch
Strongly Correlated Electrons
Elementary excitations in undoped layered cuprates
A. V. Syromyatnikov
Using the recently proposed bond-operator technique (BOT), we discuss
spin dynamics of the Heisenberg
spin-$\frac12$ antiferromagnet with the ring exchange and small interactions between the second- and the third-neighbor
spins on the square
lattice at $T=0$. This model was suggested before for description of parent compounds of high-temperature superconducting layered cuprates. BOT describes accurately short-range
spin correlations in
quantum systems and provides a quantitative description of elementary excitations which appear in other approaches as bound states of conventional low-energy quasiparticles. We demonstrate that besides well-known
magnons (
spin-1 excitations) there are three well-defined
spin-0 quasiparticles in the considered model whose energies lie near the
magnon spectrum. Two of them, the amplitude (
Higgs) mode and the quasiparticle which we named singlon, produce pronounced anomalies observed experimentally in the Raman scattering, resonant inelastic x-ray scattering, and infrared optical absorption. We find sets of the model parameters which describe quantitatively experimental data obtained in $\rm La_2CuO_4$ and $\rm Sr_2CuO_2Cl_2$.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Spin and Orbital Angular Momentum Polarization in Thouless Topological Charge Pumping
Esmaeil Taghizadeh Sisakht, Uiseok Jeong, Xiao jiang et al. (+4 more)
Quantized charge pumping in one-dimensional
chiral wires has been widely studied in the context of topological physics in a (1+1)-dimensional synthetic space, yet the role of orbital and
spin degrees of freedom in such topological pumps remains largely unexplored. Here, we examine how the topologically quantized charge pump in
insulators generates
spin polarizations, and assess whether this mechanism may offer distinct insight into the widely known
spin-selective transport in
chiral wires-commonly referred to as chirality-induced
spin selectivity. We performed time-dependent Schrodinger equations of multi-orbital tight-binding
Hamiltonians driven by a circularly polarized electric field. Our main findings are twofold. First, the intrinsic screw-like geometry of the system generates a distinctive winding structure governed by a single control parameter, in contrast to conventional adiabatic pumping mechanisms that require at least two independently modulated parameters, thereby providing a clear interpretation of one-dimensional pumping in terms of the topological structure in a (1+1)-dimensional Brillouin zone. Second, while the energy gap remains open throughout the pumping cycle, the Berry-phase driven real-time dynamics of the charge flow induces a nonequilibrium orbital polarization. Through
spin-orbit coupling, this orbital response is partially converted into
spin polarization whose direction is determined by the current and chirality. On the analogy between the synthetic (1+1)- and 2-dimensional topological
insulators, we suggest that non-trivial
spin-orbital dynamics may accompany the anomalous
quantum charge
Hall states of even-dimensional real materials.
Read the full abstract ▾
All authors Esmaeil Taghizadeh Sisakht, Uiseok Jeong, Xiao jiang, Jinseok Oh, Yizhou Liu, Binghai Yan, Noejung Park
Superconductivity
Drastic field-induced resistivity upturns as signatures of unconventional magnetism in superconducting iron chalcogenides
Z. Zajicek, I. Paulescu, P. Reiss et al. (+5 more)
Electronic scattering is a powerful tool to identify underlying changes in electronic behavior and incipient electronic and
magnetic orders. The nematic and
magnetic phases are strongly intertwined under applied pressure in FeSe, however, the additional isoelectronic substitution of sulphur offers an elegant way to separate them. Here we report the detailed
evolution of the electronic and superconducting behaviour of FeSe$_{0.96}$S$_{0.04}$ under applied pressure via longitudinal magnetoresistance studies up to 15T. At intermediate pressures, inside the nematic phase, the resistivity displays an upturn in zero
magnetic field, which is significantly enhanced in the
magnetic field, suggesting the stabilization of a
spin-density wave phase, which competes with superconductivity. At higher pressures, beyond the nematic phase boundaries, the resistivity no longer displays any clear anomalies in the zero
magnetic field, but an external
magnetic field induces significant upturns in resistivity reflecting a field-induced order, where superconductivity and
magnetic anomalies are enhanced in tandem. This study highlights the essential role of high
magnetic fields in stabilizing different electronic phases and revealing a complex interplay between magnetism and superconductivity tuned by applied pressure in FeSe$_{1-x}$S$_{x}$.
Read the full abstract ▾
All authors Z. Zajicek, I. Paulescu, P. Reiss, R. M. Abedin, K. Sun, S. J. Singh, A. A. Haghighirad, A. I. Coldea