arXiv subjects

Haiwen Liu

Publications and source records attributed to Haiwen Liu.

At least 19 recordsLinked to original sources

arXiv2026

Distinct Spatiotemporal Dynamics of Thermoelectric Transport Across Superconducting Transition

We investigate the relaxation dynamics of heat transport in superconductors, shaped by the interplay of diffusion, nonlinearity, and magnetic fields. Focusing on regimes near the critical temperature Tc, we analyze two classes of relaxation diffusion equations that give rise to qualitatively distinct dynamics, which we denote as Type I (linear) and Type II (nonlinear). Type I relaxation, characteristic of the normal state above Tc, results in a steady and spatially uniform heat current governed by linear diffusion. By contrast, Type II relaxation, relevant below Tc, exhibits non steady dynamics marked by pronounced spatial inhomogeneities and an evolving pattern, in which an initially localized hot spot propagates transiently through the system. The striking distinction between these regimes underscores a fundamental shift in transport mechanisms across the superconducting phase transition and provides experimentally relevant predictions in light of emerging techniques for probing local dissipation.

cond-mat.supr-con↗

arXiv2026

Logarithmic Aging Diffusion from a Multiplicative Event Clock: Rare Event Statistics, Ultraslow Transport, and Ensemble-Time Inequivalence

Logarithmic time dependences occur in many aging materials, but neither a $\ln t$ relaxation law nor a $1/t$ event rate uniquely identifies the underlying stochastic mechanism. We examine a specific log-aging process defined by iterating the age-conditioned forward-recurrence law after every event. This rule makes the event times multiplicative: the logarithmic ratios $U_n=\ln(T_{n+1}/T_n)$ are independent and identically distributed with an explicit non-exponential density. Consequently, both the mean and the variance of the event count grow linearly with $\ln(t/t_0)$, while the density of the $n$th event time has a log-normal central sector and a fixed-$n$ algebraic far tail. These clock statistics generate logarithmic drift and spreading, an Einstein relation under local detailed balance, and ultraslow transit and target-survival laws. They also separate trajectory reproducibility from ensemble--time equivalence: the relative scatter of the time-averaged mean-square displacement decays as $1/\ln(T/t_0)$, although its mean does not converge to the ensemble lag MSD. We distinguish the exact event-level construction from its diffusion-limit generalized Fokker--Planck and random-clock subordination representations, and from a generalized-Langevin closure that can match selected responses and covariances but need not reproduce event counts or rare-duration statistics. The proposed clock is therefore tested not by a single logarithmic curve, but by the joint, no-refitting consistency of multiplier, count, transport, first-passage, and finite-window observables.

cond-mat.stat-mech↗

arXiv2026

Eigenstate Transitions, Duality, and Anomalous Diffusion in a Quasiperiodic Qi-Wu-Zhang Chern Insulator

Quasiperiodic systems usually interpolate between extended, critical, and localized states as the quasiperiodic modulation is increased. Here we show that the magnetic Qi-Wu-Zhang Chern-insulator model realizes a distinct full-spectrum transition in which localization is avoided. For an irrational magnetic flux, the two-dimensional model reduces to a spinor quasiperiodic chain with a matrix onsite modulation controlled by the hopping amplitude $t_x$. When $|m+2|>t_y$, increasing $t_x$ produces the conventional extended-critical-localized sequence with a critical line at $t_x=t_y$. In contrast, when $|m+2|\le t_y$, the system changes from an extended phase to a critical phase at $t_x=|m+2|$ and remains critical even for stronger quasiperiodic modulation. Finite-size scaling of the average inverse participation ratio gives $\overline{\mathrm{IPR}}\sim q^{-α}$ with $0<α<1$ throughout this persistent critical regime. A dual transformation exchanging $t_x$ and $t_y$, together with a Lyapunov-exponent analysis, explains the phase diagram. Wave-packet dynamics further distinguish ballistic, anomalous-diffusive, and localized regimes. These results identify magnetic Chern-insulator systems as a natural platform for robust criticality and anomalous quantum transport.

cond-mat.dis-nn↗

arXiv2026

Quantum geometry induced anomalous chiral transport and hidden symmetry breaking in centrosymmetric 2M-WS2

Chirality, a widely existing material property in nature involving the breaking of the left-right symmetry, has profound influences in various fields of natural sciences. Nonlinear response, such as electronic magnetochiral anisotropy (eMChA), has been recognized as a sensitive probe for the effects of symmetry breaking and nontrivial quantum geometries in solids. So far, observations of eMChA have primarily been limited to inversion-symmetry broken materials. Here, we report a remarkable chiral transport in centrosymmetric candidate topological superconductor 2M-WS2 flakes observed via second-harmonic generation under an out-of-plane magnetic field. More importantly, the eMChA becomes significant around the crossover temperature TFL ~ 25 K from the Fermi liquid (FL) to strange metal (SM) in the normal state, which interestingly echoes with the anomalously large Nernst response at the same temperature in bulk 2M-WS2. These observations reveal a direct correspondence between the nonlinear response, Nernst response, and FL-SM transition in 2M-WS2. Theoretical analysis indicates that nontrivial quantum geometry is behind the simultaneous response of eMChA and Nernst effects in 2M-WS2 and the contribution from the orbital magnetic moment at the Fermi surface becomes significant during the FL-SM transition. Based on first-principles calculations, a thick-layer-sliding mechanism with minimal energy gain in 2M-WS2 provides one possibility for the generation of such nontrivial quantum geometry. The intertwined physics of remarkable eMChA, Nernst response, and FL-SM transition make 2M-WS2 a rare quantum platform to study the chiral transport and unexplored phenomena in strange metals, which may shed light on the trans-century, unresolved scientific issue in unconventional high-temperature superconductivity.

cond-mat.str-el↗

arXiv2026

Metalization of topological insulators

In modern condensed matter theory, phases of electronic matter--such as metals and insulators-are fundamentally distinguished by the presence or absence of charge-carrying quasiparticles or excitations near the Fermi surface at low temperatures. Here, we show that this criterion breaks down in Berry-curvature-dominated systems, where transport is governed by interband coherence across the entire Fermi sea. We develop a microscopic theory of quantum transport in bulk topological insulators with a vanishing density of states at the Fermi energy, for which the conventional Drude contribution is absent. We demonstrate that impurity-scattering-induced coherence decay generates a distinct longitudinal transport channel even in the topologically trivial regime, with edge contributions rigorously excluded. This mechanism yields a finite longitudinal conductivity even in the absence of carriers at the Fermi level and exhibits an unconventional scaling linear in impurity density in the dilute limit, in stark contrast to Drude behaviour. Importantly, this decoherence-induced conductance is inversely proportional to temperature, reminiscent of strange-metal behaviour, most prominently observed in cuprate superconductors above their critical temperature. Our findings reveal quantum decoherence as a fundamental origin of longitudinal transport beyond the Drude paradigm, challenging the traditional distinction between metals and insulators.

cond-mat.mes-hall↗

arXiv2026

Magnetoresistance from decoherence

Microscopic theories of magnetoresistance have traditionally focused on momentum relaxation and the plasma frequency of itinerant electrons. Here, we uncover a distinct mechanism in which magnetoresistance originates from quantum decoherence throughout the whole Fermi sea, specifically the decay of the off-diagonal components of the density matrix. The resulting conductivity, parameterized by two complex decoherence times, scales linearly with impurity density-markedly contrasting the conventional Drude picture, where conductivity is governed by momentum relaxation of Ferm-surface quasiparticles and is inversely proportional to impurity density. This unconventional scaling provides a direct electrical probe of quantum decoherence, a quantity central to both fundamental studies and emerging nanoscale technologies. Furthermore, the interplay between the external magnetic field and the exchange field gives rise to rich magnetotransport phenomena, including temperature-drive crossover from positive to negative magnetoresistance and a nonmonotonic temperature dependence with a conductivity maximum reminiscent of the Kondo effect. Our results establish quantum decoherence as a key ingredient in magnetoresistance and our findings should have an unprecedented impact on advancing research and applications involving magnetoresistance.

cond-mat.mes-hall↗

arXiv2026

Evolution from Landau Quantization to Discrete Scale Invariance Revealed by Quantum Oscillations in Topological Materials

Dirac materials have been a unique solid state platform for exploring relativistic quantum phenomena including supercritical atomic collapse, which leads to emergent discrete scale symmetry and logperiodic quantum oscillations. In the relativistic regime, the fundamental effect in quantum electrodynamics, vacuum polarization, can further modulate the atomic collapselike state by screening bare charges but is rarely harnessed in condensed matter system. Here, we report a continuous progression from low field Shubnikov de Haas oscillations to high field log periodic oscillations in the Dirac material HfTe5, with both phenomena modulated by Fermi surface anisotropy. This maps the transition from single particle Landau levels to an interaction-driven, discrete scale invariant energy spectrum of quasi-bound states. Crucially, our findings suggest vacuum polarization provides a compelling mechanism for renormalizing the effective impurity charge, quantitatively explaining the carrier-density dependent scale factor. By revealing the intricate interplay between Landau quantization, many body electronic screening, and scale-symmetry breaking, our results establish Dirac solids as a controllable platform for exploring relativistic vacuum effects and emergent novel symmetry.

cond-mat.mtrl-sci↗

arXiv2026

Theory of quantum decoherence and its application to anomalous Hall effect

Coherent quantum phenomena can only emerge when decoherence is minimized, and mastery over decoherence is technologically crucial for designing and operating functional quantum devices. However, its microscopic mechanisms in spin-orbit-coupled ferromagnets remain elusive, and quantitative treatments have long been challenging. To solve this fundamentally significant and technologically crucial problem, we develop a quantum master-equation framework with a general ansatz for the off-diagonal density matrix that simultaneously captures electric-field-driven coherence and impurity-scattering-induced decoherence. This unified approach enables quantitative analysis of how decoherence reshapes the intrinsic anomalous Hall effect, revealing a clear crossover between intrinsic and extrinsic regimes. Remarkably, we identify a previously unrecognized extrinsic contribution: a second-order scattering process tightly relative to quantum decoherence-that is fundamentally distinct from both skew scattering and side jump mechanisms, yet substantially more significant than the skew scattering mechanism. Our work establishes decoherence as a key element in quantum transport and provides a systematic extension of the Boltzmann transport equation to incorporate decoherence, with broad implications for robust spintronic functionality.

cond-mat.mes-hall↗

arXiv2026

Emergent quantum phenomena via phase-coherence engineering in infinite-layer nickelate superconductors

Dimensionality of a physical system, conventionally an invariant geometric characteristic, fundamentally governs the universality class of phase transitions and the landscape of emergent collective phenomena. In low-dimensional or layered high-temperature superconductors, the macroscopic phase coherence of superconducting orders is typically confined in two dimensions, underscoring the critical role of phase fluctuations in determining the overall phase diagrams. Here, we strategically enhance the phase fluctuations by fabricating periodically arranged nano-holes in the infinite-layer nickelate superconducting films, effectively constructing Josephson junction arrays. In the nano-patterned films, the weakening of macroscopic phase coherence drives a two-stage superconducting transition towards an anomalous metallic ground state with saturated resistance. The emergence of charge-2e quantum oscillations manifests the coherence across the array, while an anomalous zero-field magnetoresistance peak signifies the extreme quantum phase fluctuations persisting to ultralow temperatures. Remarkably, with quantum fluctuations enhanced synergistically by nano-patterning and magnetic fields, an anomalous reversal of superconducting anisotropy is observed in Nd-nickelates, where in-plane critical fields fall below out-of-plane values. The evolution of anisotropy may unmask an internal exchange-Zeeman field coupled to the collective electronic states. Our results unveil how superconductivity evolves in response to phase fluctuations, establishing nano-patterning as a powerful paradigm to uncover hidden intertwined orders in strongly correlated systems.

cond-mat.supr-con↗

arXiv2026

APT-MCL: An Adaptive APT Detection System Based on Multi-View Collaborative Provenance Graph Learning

Advanced persistent threats (APTs) are stealthy and multi-stage, making single-point defenses (e.g., malware- or traffic-based detectors) ill-suited to capture long-range and cross-entity attack semantics. Provenance-graph analysis has become a prominent approach for APT detection. However, its practical deployment is hampered by (i) the scarcity of APT samples, (ii) the cost and difficulty of fine-grained APT sample labeling, and (iii) the diversity of attack tactics and techniques. Aiming at these problems, this paper proposes APT-MCL, an intelligent APT detection system based on Multi-view Collaborative provenance graph Learning. It adopts an unsupervised learning strategy to discover APT attacks at the node level via anomaly detection. After that, it creates multiple anomaly detection sub-models based on multi-view features and integrates them within a collaborative learning framework to adapt to diverse attack scenarios. Extensive experiments on three real-world APT datasets validate the approach: (i) multi-view features improve cross-scenario generalization, and (ii) co-training substantially boosts node-level detection under label scarcity, enabling practical deployment on diverse attack scenarios.

cs.CR↗

arXiv2025

Right-eigenstate-based approach to non-Hermitian superfluidity with two-body loss

We theoretically explore a non-Hermitian superfluid model with complex-valued interaction, inspired by two-body loss stemming from inelastic scattering observed in ultracold atomic experiments. Utilizing both the right-eigenstate-based mean-field theory and its biorthogonal counterpart, we study the properties of the system. Notably, the right-eigenstate-based framework produces smooth and continuous solutions, in stark contrast to the absence of nontrivial solutions and the abrupt discontinuities observed in the biorthogonal-eigenstate-based framework under moderate dissipation. In addition, the lower condensation energy obtained in the former framework suggests its superior suitability for describing this system. Furthermore, we explore the impact of backscattering, a crucial factor in realistic systems. Our analysis reveals that, facilitated by two-body loss, even moderate backscattering destabilizes the superfluid state. Sufficiently strong backscattering completely destroys it, highlighting a key mechanism for the fragility of this non-Hermitian quantum phase.

cond-mat.quant-gas↗

arXiv2025

First-Order PT Phase Transition in Non-Hermitian Superconductors

The interplay between superconductivity and environmental dissipation, effectively captured by non-Hermitian Hamiltonian, is a new frontier for exotic quantum phases. We explore a PT-symmetric non-Hermitian superconductor with balanced gain and loss. To ensure experimental relevance, we develop a right-eigenstate-based non-Hermitian mean-field theory. We uncover a novel first-order phase transition that coincides exactly with the PT symmetry breaking point, driven by the interplay between superconducting pairing interactions and non-Hermitian dissipation. In the PT-symmetric phase, moderate NH dissipation enhances superconductivity, while in the PT-broken phase, intensified dissipation significantly suppresses it. These phenomena, characterized by abrupt jumps in observables, can be probed through localized spectral measurements and macroscopic superfluid density analysis. Additionally, the stability analysis offers robust theoretical insights to support experimental investigations of this unique transition.

cond-mat.supr-con↗

arXiv2025

Superconducting gap and its Little-Parks like oscillations with high-order harmonics in lithium intercalated 1T-TiSe$_2$

The superconducting phase of doped 1T-TiSe$_2$ is a fruitful playground for exploring exotic quantum phenomena such as the anomalous metal state and spontaneously formed superconducting network. Here, we address these emergent states by studying the superconducting gap of lithium intercalated TiSe$_2$-a fundamental quantity that has remained unexplored so far. We fabricate a device that combines solid-state lateral lithium intercalation, resistance measurements and tunneling spectroscopy. We successfully probe the superconducting gap of TiSe$_2$ and reveal that the gap closing temperature well exceeds the transition temperature ($T_c$) expected from the Bardeen-Cooper-Schrieffer theory, indicating pronounced superconducting fluctuations even in a bulk-like system. Moreover, the symmetric gap persists even in the anomalous metal state, demonstrating the particle-hole symmetry of this exotic phase directly from the density of states. Finally, the superconducting gap shows magneto-oscillations with higher harmonics, attesting to a rather regular structure of the intrinsic superconducting network.

cond-mat.supr-con↗

arXiv2025

Exceedingly large in-plane critical field of finite-momentum pairing state in bulk superlattices

Magnetic flux profoundly influences the phase factor of charge particles, leading to exotic quantum phenomena. A recent example is that the orbital effect of magnetic field could induce finite-momentum pairing state in nanoflakes, which offers a new pathway to realize the spatially modulated superconductivity distinct from the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state induced by Zeeman effect. However, whether such intriguing state can exist in the bulk materials under extremely large magnetic field remains elusive. Here we report the orbital effect induced finite-momentum pairing state with exceedingly large in-plane critical field in a bulk superconducting superlattice. Remarkably, the in-plane critical field shows a pronounced upturn behavior, exceeding eight times the Pauli limit which is comparable to monolayer Ising superconductor. Under high in-plane magnetic fields, significant anisotropic transport behavior between the interlayer and intralayer directions is detected, highlighting the critical role of suppressed interlayer coherence in the orbital effect induced finite-momentum pairing state. Crucially, this finite-momentum pairing state remains robust against moderate disorder. Our findings suggest that van der Waals superlattices, with strong Ising spin-orbit coupling and tunable interlayer coherence, offer new avenues for constructing and modulating unconventional superconducting states.

cond-mat.supr-con↗

arXiv2025

Dimensionality-Driven Anomalous Metallic State with Zero-field Nonreciprocal Transport in Layered Ising Superconductors

The anomalous metal state (AMS), observed in failed superconductors, provides insights into superconductivity and quantum criticality, with studies revealing unconventional quantum phases like the Bose metal. Recently, layered transition metal dichalcogenide (TMD) superconductors approaching the two-dimensional limit have garnered significant attention for the enhanced phase fluctuations and electronic correlations. Investigating AMS in these systems, particularly in the absence of an external magnetic field, could offer valuable insights into the dimensionality-driven emergence of exotic quantum phenomena, including triplet Cooper pairing, phase fluctuation dynamics, and especially the recently discovered field-free superconducting diode effects. However, the field-free AMS has yet to be observed in TMD superconductors. Here, we report the dimensionality-tunable AMS near the superconducting quantum phase transitions in a layered TMD superconductor 2H-Ta2S3Se. In samples with thicknesses below 10 nm, we demonstrate magnetic field-driven AMS under external magnetic field, characterized by the vanishing of the Hall resistance and the presence of finite longitudinal resistance. Remarkably, an unexpected zero-field AMS emerges as the sample thickness is reduced to 3 nm. This AMS aligns well with the quantum vortex creep model and exhibits non-reciprocal transport behaviors, suggesting the onset of spontaneous time-reversal symmetry breaking accompanied by vortex motion as the system approaches the two-dimensional limit. Our findings open new avenues for exploring dimensionality-driven exotic superconducting quantum critical phases, and pave the way for a deeper understanding of zero-field superconducting diode effects.

cond-mat.supr-con↗

arXiv2025

Rare-Event-Induced Ergodicity Breaking in Logarithmic Aging Systems

Ergodicity breaking and aging effects are fundamental challenges in out-of-equilibrium systems. Various mechanisms have been proposed to understand the non-ergodic and aging phenomena, possibly related to observations in systems ranging from structural glass and Anderson glasses to biological systems and mechanical systems. While anomalous diffusion described by Levy statistics efficiently captures ergodicity breaking, the origin of aging and ergodicity breaking in systems with ultraslow dynamics remain unclear. Here, we report a novel mechanism of ergodicity breaking in systems exhibiting log-aging diffusion. This mechanism, characterized by increasingly infrequent rare events with aging, yields statistics deviating significantly from Levy distribution, breaking ergodicity as shown by unequal time- and ensemble-averaged mean squared displacements and two distinct asymptotic probability distribution functions. Notably, although these rare events contribute negligibly to statistical averages, they dramatically change the system's characteristic time. This work lays the groundwork for microscopic understanding of out-of-equilibrium systems and provides new perspectives on glasses and Griffiths-McCoy singularities.

cond-mat.dis-nn↗

arXiv2025

Quantum fluctuations-driven Melting Transitions in Two-dimensional Superconductors

Quantum fluctuations are pivotal in driving quantum phase transitions, exemplified by the quantum melting of Wigner crystals into Fermi liquids in electron systems. However, their impact on superconducting systems near zero temperature, particularly in the superconductor-insulator/metal transition, remains poorly understood. In this study, through electric transport measurements on the two-dimensional (2D) superconductor (SnS)1.17NbS2, we demonstrate that quantum fluctuations induce vortex displacement from their mean position, leading to the quantum melting of vortex solid near zero temperature. Quantitative analysis reveals the magnetic field-induced anomalous metal originates from this quantum melting transition, with energy dissipation governed by quantum fluctuations-driven vortex displacements. Remarkably, further extending this analysis to various 2D superconductors yields the same results, and many properties of anomalous metal can be qualitatively understood within the framework of quantum melting. The connection between the quantum melting of vortex solids and dissipative anomalous metal opens a novel pathway towards understanding quantum phase transitions through vortex dynamics, providing new insights on both fields.

cond-mat.supr-con↗

arXiv2024

Quantum Griffiths singularity in a three-dimensional superconductor to Anderson critical insulator transition

Disorder is ubiquitous in real materials and can have dramatic effects on quantum phase transitions. Originating from the disorder enhanced quantum fluctuation, quantum Griffiths singularity (QGS) has been revealed as a universal phenomenon in quantum criticality of low-dimensional superconductors. However, due to the weak fluctuation effect, QGS is very challenging to detect experimentally in three-dimensional (3D) superconducting systems. Here we report the discovery of QGS associated with the quantum phase transition from 3D superconductor to Anderson critical insulator in a spinel oxide MgTi2O4 (MTO). Under both perpendicular and parallel magnetic field, the dynamical critical exponent diverges when approaching the quantum critical point, demonstrating the existence of 3D QGS. Among 3D superconductors, MTO shows a relatively strong fluctuation effect featured as a wide superconducting transition region. The enhanced fluctuation, which may arise from the mobility edge of Anderson localization, finally leads to the occurrence of 3D quantum phase transition and QGS. Our findings offer a new perspective to understand quantum phase transitions in strongly disordered 3D systems.

cond-mat.supr-con↗