arXiv subjects

Yong-Feng Yang

Publications and source records attributed to Yong-Feng Yang.

5 recordsLinked to original sources

arXiv2026

Interaction-Split Edge Spectral Flow in an Integer Hubbard Thouless Pump

We show that local Hubbard correlations can split the open-boundary spectral flow of an otherwise integer Thouless pump. Using density-matrix renormalization group calculations for a period-three Hubbard chain with a sliding onsite-repulsion modulation, we identify at filling $\rho=2/3$ a correlated insulating pump with many-body Chern number $C=+2$, corresponding to two units of charge transported per cycle. A spin-degenerate Hartree/Aubry--Andr\'e--Harper reference model realizes the same integer response through simultaneous edge spectral flow in two independent spin channels. In the full Hubbard model, however, this integer bulk pump is implemented differently at an open boundary: the edge flow separates into two boundary events, and the intervening low-energy state is a nearly charge-neutral triplet edge excitation. Thus the quantized bulk charge transport remains integer, but local correlations reorganize its boundary realization into separated charged and neutral spinful sectors.

cond-mat.str-el↗

arXiv2025

On the criticality of the configuration-space statistical geometry

While phases and phase transitions are conventionally described by local order parameters in real space, we present a unified framework characterizing the phase transition through the geometry of configuration space defined by the statistics of pairwise distances $r_H$ between configurations. Focusing on the concrete example of Ising spins, we establish crucial analytical links between this geometry and fundamental real-space observables, i.e., the magnetization and two-point spin correlation functions. This link unveils the universal scaling law in the configuration space: the standard deviation of the normalized distances exhibits universal criticality as $\sqrt{\mathrm{Var}(r_H)}\sim L^{-2\beta/\nu}$, provided that the system possesses zero magnetization and satisfies $4\beta/\nu < d$. We validate this scaling with stochastic series expansion quantum Monte Carlo simulations of the transverse-field Ising model(TFIM). Furthermore, we propose configuration-space diagnostics that go beyond local real-space observables. First, the distribution probability $P(r_H)$ parameterized by the transverse field $h$ forms a one-dimensional manifold. Information-geometric analyses, particularly the Fisher information defined on this manifold, successfully pinpoint the TFIM phase transition, regardless of the measurement basis. Second, for the Su-Schrieffer-Heeger Heisenberg model, a parity index derived from $P(r_H)$ successfully characterizes the symmetry-protected topological phase and its transition. Our work establishes configuration space geometry as a novel perspective on quantum criticality, revealing how macroscopic universal phenomena are encoded within its global statistical features.

cond-mat.stat-mech↗

arXiv2023

Disorder in interacting quasi-one-dimensional systems: flat and dispersive bands

We investigate the superconductor-insulator transition (SIT) in disordered quasi-one dimensional systems using the density-matrix renormalization group method. Focusing on the case of an interacting spinful Hamiltonian at quarter-filling, we contrast the differences arising in the SIT when the parent non-interacting model features either flat or dispersive bands. Furthermore, by comparing disorder distributions that preserve or not SU(2)-symmetry, we unveil the critical disorder amplitude that triggers insulating behavior. While scaling analysis suggests the transition to be of a Berezinskii-Kosterlitz-Thouless type for all models (two lattices and two disorder types), only in the flat-band model with Zeeman-like disorder the critical disorder is nonvanishing. In this sense, the flat-band structure does strengthen superconductivity. For both flat and dispersive band models, i) in the presence of SU(2)-symmetric random chemical potentials, the disorder-induced transition is from superconductor to insulator of singlet pairs; ii) for the Zeeman-type disorder, the transition is from superconductor to insulator of unpaired fermions. In all cases, our numerical results suggest no intermediate disorder-driven metallic phase.

cond-mat.str-el↗

arXiv2022

Observation of many-body Fock space dynamics in two dimensions

Quantum many-body simulation provides a straightforward way to understand fundamental physics and connect with quantum information applications. However, suffering from exponentially growing Hilbert space size, characterization in terms of few-body probes in real space is often insufficient to tackle challenging problems such as quantum critical behavior and many-body localization (MBL) in higher dimensions. Here, we experimentally employ a new paradigm on a superconducting quantum processor, exploring such elusive questions from a Fock space view: mapping the many-body system onto an unconventional Anderson model on a complex Fock space network of many-body states. By observing the wave packet propagating in Fock space and the emergence of a statistical ergodic ensemble, we reveal a fresh picture for characterizing representative many-body dynamics: thermalization, localization, and scarring. In addition, we observe a quantum critical regime of anomalously enhanced wave packet width and deduce a critical point from the maximum wave packet fluctuations, which lend support for the two-dimensional MBL transition in finite-sized systems. Our work unveils a new perspective of exploring many-body physics in Fock space, demonstrating its practical applications on contentious MBL aspects such as criticality and dimensionality. Moreover, the entire protocol is universal and scalable, paving the way to finally solve a broader range of controversial many-body problems on future larger quantum devices.

quant-ph↗

arXiv2021

Enhanced superconductivity and various edge modes in modulated $t$-$J$ chains

We numerically investigate the ground state of the extended $t$-$J$ Hamiltonian with periodic local modulations in one dimension by using the density-matrix renormalization group method. Examining charge and spin excitation gaps, as well as the pair binding energy, with extrapolated results to the thermodynamic limit, we obtain a rich ground-state phase diagram consisting of the metallic state, the superconducting state, the phase separation, and insulating states at commensurate fillings. Compared to the homogeneous 1D $t$-$J$ model, the superconductivity is greatly enhanced and stabilized by the flat-band structure. This superconducting state in quasi-periodic chains shares similar properties with ladder systems: significant negative pair binding energy occurs, and the singlet pairing correlation function dominates with the algebraic decay while the single-particle Green's function and spin correlation function decay exponentially. On the other hand, quasi-periodicity leads to nontrivial topological nature in insulating states, characterized by different integer Chern numbers at different fillings. Due to the interplay among the topology, the interaction, and the 1D confinement, gapless edge modes show strong spin-charge separation and in different regions can relate to different collective modes, which are the charge of a single fermion, the magnon, and the singlet-pair. We also find two interaction driven topological transitions: i) at particle filling $ρ=1/2$, the low-energy edge excitations change from the magnon to singlet-pair, accompanied with pair formation in bulk; and ii) at $ρ=3/4$, while the gapless edge mode remains the charge of a single fermion, there is a gap-closing point and a $π$-phase shift in the quasi-particle spectrum.

cond-mat.str-el↗