arXiv subjects

SungBin Lee

Publications and source records attributed to SungBin Lee.

At least 19 recordsLinked to original sources

arXiv2026

Ab initio screening of quantum frustrated materials with kagome and triangular geometries

Geometrical frustration is a powerful route to realize exotic phases such as quantum spin liquids. Despite extensive efforts, systematic searches targeting specific frustration motifs and their potential to host unconventional magnetic ground states remain rare, thus highlighting the need for a more focused and predictive materials discovery approach. Here we present a new strategy combining high-throughput first-principles calculations, magnetic force theory, and spin Hamiltonian analysis. Starting from the 150,000 material database, we catalogue candidate materials that may host competing exchange interactions and new types of magnetic states with the focus on kagome or triangular lattices. Our workflow not only reproduces the majority of known frustrated magnetic materials, validating our approach, but also predicts novel candidate compounds with targeted frustration profiles that have not yet been experimentally synthesized. Among these, we identify six promising new materials: one triangular lattice compound, KMgNiIO6, and five kagome lattice compounds; Li4Fe3WO8, Li2V3F8, Li5VP2(O4F)2, and Li2MgCo3O8 (P2/m and C2/m). For each candidate, we identify detailed magnetic properties and further propose their potential magnetic ground states, revealing that some of them may host entirely new magnetic phases driven by their distinct frustration characteristics.

cond-mat.str-el↗

arXiv2026

Spin Liquid Landscapes in the Kagome Lattice: A Variational Monte Carlo Study of the Chiral Heisenberg Model and Experimental Signatures

Chiral spin liquids, which break time-reversal symmetry, are of great interest due to their topological properties and fractionalized excitations (anyons). In this work, we investigate chiral spin liquids (CSL) on the kagome lattice arising from the competition between the third-nearest-neighbor Heisenberg interaction across hexagons ($J_d$) and a staggered scalar spin chirality term ($J_χ$). Using variational Monte Carlo methods, we map out the phase diagram and identify various gapped and gapless CSL phases, each characterized by a distinct flux pattern. Notably, the interplay between $J_d$ and $J_χ$ induces a tricritical point, which we analyze using Landau-Ginzburg theory. Additionally, we identify potential signatures of these CSLs-including distinctive spin-spin correlations, anomalies in the static spin structure factor, longitudinal thermal conductivity, and magentoelectric effects-which offer practical guidance for their future experimental detection.

cond-mat.str-el↗

arXiv2025

All-to-All interactions via multifractal wavefunction geometry

We uncover a generic mechanism through which the intrinsic geometry of multifractal quantum wavefunctions generates effective all-to-all interactions in many-body systems. By analyzing the multifractal spectrum, we demonstrate that the simultaneous participation of widely separated length scales creates a global connectivity that bypasses local interaction constraints. This nonlocality leads to fast information scrambling, evidenced by sharp changes in the quenched dynamics of the quantum Fisher information and bipartite mutual information with the onset of negative tripartite mutual information. Such rapid scrambling is a defining feature of strongly chaotic quantum dynamics, and our results identify the systems with multifractal states as a promising solid-state platform for realizing this regime. More broadly, they reveal a new paradigm in which complex, multiscale wavefunction structure intrinsically generates long-range connectivity, providing a natural route to achieving nonlocal behavior in strongly correlated quantum materials.

cond-mat.str-el↗

arXiv2025

Spatial correlations of charge density wave order across the transition in 2H-NbSe2

Charge density waves (CDWs) involve coupled amplitude and phase degrees of freedom, but direct access to local amplitude correlations remains experimentally challenging. Here, we report cryogenic four-dimensional scanning transmission electron microscopy (4D-STEM) measurements of CDW ordering in a 2H-NbSe2 flake of 24 nm thickness, enabled by liquid helium-based cooling. By mapping the spatial distribution of CDW superlattice intensities at nanometer-scale resolution and analyzing their autocorrelations, we extract the temperature-dependent correlation length associated with the local amplitude of the CDW order parameter, independent of global phase coherence. Our results reveal that a finite local CDW amplitude is already established well above the transition temperature. When the system is cooled below the transition temperature down to 20 K, the correlation length extends to nearly 110 nm, and the local CDW amplitude is found to strongly anticorrelate with the local strain field.

cond-mat.str-el↗

arXiv2025

Entanglement switching via mobility edges in a quasiperiodic chain

We propose quasiperiodic chains with tunable mobility edge physics, as a promising platform for engineering long-range quantum entanglement. Using the generalized Aubry-André model, we show that the mobility edges play a key role in manipulating long-range indirect interactions in these systems. Near the mobility edge, critical states exhibit unexpectedly strong correlations between sites that share similar local structures, regardless of their spatial separation. Remarkably, by tuning the mobility edge across the Fermi level, one can induce both adiabatic transport and abrupt switching of entanglement between distant sites. These results highlight the potential of aperiodic structures for controlling nonlocal quantum correlations, opening new avenues for entanglement-based applications in quasiperiodic systems.

cond-mat.str-el↗

arXiv2025

Interaction tuned pattern-selective superconductivity: Application to the dodecagonal quasicrystal

Quasicrystals exhibit superconductivity under the unique interplay of long-range order and strong inhomogeneity, distinguishing them from both crystalline and amorphous systems. Understanding how this structural complexity affects superconducting states and phase transitions remains an important open question. Here, we unveil anomalous superconductivity in a dodecagonal quasicrystal using the attractive Hubbard model within the Bogoliubov-de Gennes framework. We show that both the gap structure and critical temperature depend on the local pattern due to inhomogeneous charge distribution and kinetic terms. This leads to unconventional phase transitions between mixed phases where superconducting and normal metal regions coexist, even without external fields, which we term pattern-selective superconductivity. Furthermore, superconductivity can be anomalously suppressed even under stronger attractive interactions due to the alignment of the Fermi level with a spectral gap in the fragmented Hartree-shifted spectrum. These findings, not observed in conventional crystals, amorphous systems, or previous studies of quasicrystal superconductivity, highlight the distinct role of quasicrystalline order.

cond-mat.supr-con↗

arXiv2025

Multi-orbital effects on superconductivity in kagome metals: Parquet renormalization group analysis

The Van Hove singularities (VHSs), where the electronic density of states diverges due to saddle points in the band structure, play a crucial role in enhancing electronic correlations and driving various instabilities. In particular, VHS-induced superconductivity has earned significant attention due to its potential to achieve high transition temperatures and its tendency to favor exotic pairing states beyond conventional electron-phonon mechanisms. Despite extensive research on VHS-driven superconductivity, the multi-orbital effect on such systems remains less explored. Motivated by recent experiments on several kagome metals under doping and pressure [Z.Zhang {\it et al.}, Phys.Rev.B {\bf 103}, 224513 (2021), Y.Sur {\it et al.}, Nat.Commun. {\bf 14}, 3899 (2023)], we explore the effects of multi-orbital physics and strong correlations induced by VHS in the kagome lattice, focusing on their impact on superconductivity. Using parquet renormalization group analysis, we uncover eight distinct superconducting instabilities, characterized by order parameters with mixed orbital degrees of freedom. Among these, we identify a parameter regime where $d$-wave-like orbital-singlet spin-triplet order parameters dominate as the leading instability. The degenerate spin-triplet states in this regime are capable of breaking time-reversal symmetry, which is a multi-orbital analogue of chiral spin-triplet superconductivity. These findings highlight the interplay between multi-orbital effects on superconductivity and can apply to the kagome metal systems such as $A$V$_3$Sb$_5$ ($A$ = K, Rb, Cs) family.

cond-mat.str-el↗

arXiv2025

Reallocation of Nonlocal Entanglement in Incommensurate Cold Atom Arrays

Cold atom arrays in optical lattices offer a highly tunable platform for exploring complex quantum phenomena that are difficult to realize in conventional materials. Here, we investigate the emergence of controllable long-range quantum correlations in a simulated twisted bilayer structure with fermionic cold atoms. By exploiting the incommensurate nature of the twisted bilayer, we observe a significant enhancement of long-range susceptibility, suggesting the formation of stable entangled states between spatially distant localized spins. We further show that the tunability of the interlayer coupling in terms of driving fields enables us to manipulate these entangled states without deformation of lattice structure and extra doping. Our findings provide a pathway for overcoming challenges in establishing strong correlations across distant sites, highlighting the potential of optical lattices as a versatile platform for advanced quantum technologies.

cond-mat.quant-gas↗

arXiv2024

Graph theoretical proof of nonintegrability in quantum many-body systems : Application to the PXP model

A rigorous proof of integrability or non-integrability in quantum many-body systems is among the most challenging tasks, as it involves demonstrating the presence or absence of local conserved quantities and deciphering the complex dynamics of the system. In this paper, we establish a graph-theoretical analysis as a comprehensive framework for proving the non-integrability of quantum systems. Exemplifying the PXP model, which is widely believed to be non-integrable, this work rigorously proves the absence of local conserved quantities, thereby confirming its non-integrability. This proof for the PXP model gives several important messages not only that the system is non-integrable, but also the quantum many body scaring observed in the model is not associate with the existence of local conserved quantities. From a graph-theoretical perspective, we also highlight its advantage, even in integrable systems, as the classification of local conserved quantities can be achieved by simply counting the number of isolated loops in the graphs. Our new approach is broadly applicable for establishing proofs of (non-)integrability in other quantum many-body systems, significantly simplifying the process of proving nonintegrability and giving numerous potential applications.

cond-mat.stat-mech↗

arXiv2024

Proof of nonintegrability of the spin-$1$ bilinear-biquadratic chain model

Spin-$1$ chain models have been extensively studied in condensed matter physics, significantly advancing our understanding of quantum magnetism and low-dimensional systems, which exhibit unique properties compared to their spin-$1/2$ counterparts. Despite substantial progress in this area, providing a rigorous proof of nonintegrability for the bilinear-biquadratic chain model remains an open challenge. While integrable solutions are known for specific parameter values, a comprehensive understanding of the model's general integrability has been elusive. In this paper, we present the first rigorous proof of nonintegrability for the general spin-$1$ bilinear-biquadratic chain models. Our proof not only confirms the nonintegrability of widely studied models but also extends to offer deeper insights into several areas. These include the unification of nonintegrability proofs using graph theoretical methods and the identification of the absence of local conserved quantities in quantum many-body scar systems with perfect fidelity revivals, such as the AKLT model. This work marks a significant step toward understanding the complex dynamics of spin-$1$ systems and offers a framework that can be applied to a broader class of quantum many-body systems.

cond-mat.stat-mech↗

arXiv2024

Hidden hyperspace geometry and long-distance quantum coupling

Most periodic systems are governed by short-range interactions as long-range interactions in these systems diminish uniformly. In this letter, however, we demonstrate that this is not true for a more general class of systems, which possess long-range order without periodicity, known as quasiperiodic systems. Quasiperiodicity alters the well-known characteristics of the long-range couplings, resulting in anomalous enhancement for arbitrarily long distances, even beyond the mesoscopic scale. By exemplifying the indirect spin exchange interaction, we show that the long-range coupling in a quasiperiodic chain does not attenuate over distance but is instead governed by a novel distance metric, we have named the hyperspace geometric distance. This enables us to remotely control the spins over even mesoscopic distances. Our work provides new paradigms of strongly correlated physics applicable to a broader class of systems beyond the conventional ones.

cond-mat.str-el↗

arXiv2024

Immortal quantum correlation in quasiperiodic quasi-1D system

The prevailing view on long-range correlations is that they typically attenuate uniformly with distance and temperature, as most interactions either exhibit short-range dominance or decay following a power law. In contrast to this belief, this study demonstrates that the intricate interplay between quasiperiodicity and the quasi-1D nature of subbands can result in strong long-range coupling without attenuation, a phenomenon referred to as an immortal interaction. Exemplifying a periodically stacked Fibonacci chain, we uncover an immortal interaction with greatly enhanced, persistent long-range coupling. Using negativity, it is shown that this interaction creates stable entanglement that endures over long distances and remains robust at finite temperatures. Additionally, unconventional logarithmic scaling entanglement is revealed, deviating from the traditional area law. These findings offer quasiperiodic quasi-1D systems as a novel platform for sustaining stable entanglement across exceptionally long distances, even in the presence of finite temperature effects.

cond-mat.str-el↗

arXiv2024

Controllable Skyrmion Islands in a Moiré Magnet

Antiferromagnetic(AFM) skyrmions have been in the spotlight as ideal topological magnetic bits. Although they are topologically protected, they do not exhibit the skyrmion Hall effect unlike the ferromagnetic ones. Thus, AFM skyrmions are considered to provide a better control of the skyrmion's motion due to the absence of the skyrmion Magnus effect. In this work, we propose a possible realization of controllable AFM skyrmions in a twisted Moiré magnet. The tunability of Moiré materials is not only a good platform for the provision of rich phases, but also for the stabilization of skyrmion phase. We investigate the ground state of twisted bilayer AFM system by solving the Landau-Lifshitz-Gilbert equation in a continuum model. We show that the AFM skyrmions are stabilized even in the absence of the external/dipolar magnetic field, as a consequence of the interplay of interlayer coupling, Dzyaloshinskii-Moriya (DM) interaction and Ising anisotropy. More interestingly, due to the magnetoelectric effect, the application of an external electric field locally stabilizes the skyrmions in the twisted bilayer AFM systems, even in the absence of DM interaction. It also allows the skyrmion helicity to change continuously when both the DM interaction and an electric field are present. We show the phase diagram with respect to the strength of interlayer coupling, the DM interaction and an electric field. Our results suggest the possibility of using AFM skyrmions as stable, controllable topological magnetic bits.

cond-mat.mes-hall↗

arXiv2023

Unveiling unique properties of icosahedral magnetic quasicrystals -- Multipole physics and frustration

Multipolar degrees of freedom and their hidden orders have been widely discussed in the context of heavy fermions, frustrated magnets and exotic Kondo effects. Although there has been extensive search for multipolar degrees of freedom in magnetic systems, there are few examples that allow pure multipolar degrees of freedom in the absence of magnetic dipoles. In this work, for the first time, we show that the magnetic behavior in an icosahedral quasicrystal is generally described by multipolar degrees of freedom, and in a specific case by the pure magnetic octupoles in the absence of dipoles, resulting from the interplay of spin orbit coupling and crystal field splitting. Importantly, we point out the non-crystallographic symmetries lead to multipolar degrees of freedom, only allowed in quasicrystals but forbidden in conventional crystals. For both Kramers and non-Kramers doublets, the characteristics of multipoles are classified and the effective spin Hamiltonian on symmetry grounds are derived. Based on the self-similar triangular structure of the icosahedron, we argue the long-range frustration in terms of the Ising model. We further classify the possible quantum phases including quantum fluctuations, in terms of the instantaneous entanglement generation of the ground state. Our study offers the magnetic icosahedral quasicrystal as a new platform to search for the novel multipolar degrees of freedom and their exotic phenomena.

cond-mat.str-el↗

arXiv2023

Localization control born of intertwined quasiperiodicity and non-Hermiticity

Quasiperiodic systems are neither randomly disordered nor translationally invariant in the absence of periodic length scales. Based on their incommensurate order, novel physical properties such as critical states and self-similar wavefunctions have been actively discussed. However, in open systems generally described by the non-Hermitian Hamiltonians, it is hardly known how such quasiperiodic order would lead to new phenomena. In this work, we show for the first time that the intertwined quasiperiodicity and non-Hermiticity can give rise to striking effects: perfect delocalization of the critical and localized states to the extended states. In particular, we explore the wave function localization character in the Aubry-Andre-Fibonacci (AAF) model where non-reciprocal hopping phases are present. Here, the AAF model continuously interpolates the two different limit between metal to insulator transition and critical states, and the nonHermiticity is encoded in the hopping phase factors. Surprisingly, their interplay results in the perfect delocalization of the states, which is never allowed in quasiperiodic systems with Hermiticity. By quantifying the localization via inverse participation ratio and the fractal dimension, we discuss that the non-Hermitian hopping phase leads to delicate control of localization characteristics of the wave function. Our work offers (1) emergent delocalization transition in quasiperiodic systems via non-Hermitian hopping phase, (2) detailed localization control of the critical states, In addition, we suggest an experimental realization of controllable localized, critical and delocalized states, using photonic crystals.

quant-ph↗

arXiv2023

Fractionalization induced structural domain patterns in U(1) quantum spin liquids

The emergence of fractionalized quasiparticles in quantum spin liquids has served a wealth of unconventional phenomena in frustrated magnets. In our work, we explore the various domain patterns of such fractionalized quasiparticles, especially focusing on charge defects in U(1) quantum spin liquids. We claim that emergent long range interaction between charge defects leads to characteristic structures with distinct length scales, where they can be controlled via the ratio of interaction strengths. In this context, the spin ice phase is the dilute gas of weakly interacting charges, whereas, the macroscopic population of charge defects naturally develops charge ordering for large Coulomb interaction limit. Interestingly, we find that the competing spin interactions could naturally give rise to stabilize the mosaic structure of charge defects in the absence of uniform ordering. They are characterized by liquid-like correlations having a finite length scale. The emergence of such intermediate order in the mosaic structure is confirmed by both dynamical and static correlations. By establishing the microscopic spin Hamiltonian, we also present the distinctive signatures in static spin correlation to detect such spatial structure of charge defects. We speculate that the domain pattern of defect population might be a potential hallmark to reveal unusual dynamical properties observed in spin liquids.

cond-mat.str-el↗

arXiv2022

Subharmonic fidelity revival in a driven PXP model

The PXP model hosts a special set of nonergodic states, referred to as quantum many-body scars. One of the consequences of quantum scarring is the periodic revival of the wave function fidelity. It has been reported that quantum fidelity revival occurs in the PXP model for certain product states, and periodic driving of chemical potential can enhance the magnitude of quantum revival, and can even change the frequencies of revival showing the subharmonic response. Although the effect of the periodic driving in the PXP model has been studied in the limit of certain perturbative regimes, the general mechanism of such enhanced revival and frequency change has been barely studied. In this work, we investigate how periodic driving in the PXP model can systematically control the fidelity revival. Particularly, focusing on the product state so called a Neel state, we analyze the condition of driving to enhance the magnitude of revival or change the frequencies of revival. To clarify the reason of such control, we consider the similarities between the PXP model and the free spin-1/2 model in graph theoretical analysis, and show that the quantum fidelity feature in the PXP model is well explained by the free spin-1/2 model. In addition, under certain limit of the driving parameters, analytic approach to explain the main features of the fidelity revival is also performed. Our results give an insight of the scarring nature of the periodically driven PXP model and pave the way to understand their (sub-)harmonic responses and controls.

cond-mat.quant-gas↗

arXiv2022

Intertwining orbital current order and superconductivity in Kagome metal

The nature of superconductivity in newly discovered Kagome materials, $\text{AV}_3\text{Sb}_5$ (A=K, Rb, Cs), has been a subject of intense debate. Recent experiments suggest the presence of orbital current order on top of the charge density wave (CDW) and superconductivity. Since the orbital current order breaks time-reversal symmetry, it may fundamentally affect possible superconducting states. In this work, we investigate the mutual influence between the orbital current order and superconductivity in Kagome metal with characteristic van Hove singularity (vHS). By explicitly deriving the Landau-Ginzburg theory, we classify possible orbital current order and superconductivity. It turns out that distinct unconventional superconductivities are expected, depending on the orbital current ordering types. Thus, this information can be used to infer the superconducting order parameter when the orbital current order is identified and vice versa. We also discuss possible experiments that may distinguish such superconducting states coexisting with the orbital current order.

cond-mat.supr-con↗