arXiv subjects

Zhi-Hua Li

Publications and source records attributed to Zhi-Hua Li.

4 recordsLinked to original sources

arXiv2025

Infinite temperature transport in the strong coupling regime of a nonintegrable quantum spin chain

We study spin transport of the XXZ model with next-nearest neighbor $Δ_2$ terms. We compute numerically dependence of spin conductivity $σ(ω)$ on the anisotropy $Δ$ and the ratio $r= Δ_2/Δ$, in the large $Δ$ regime. We find that, when $0<r<1$, the low-frequency conductivity assumes an anomalous form $σ(ω)\approx a ω^2 + b Δ^{-2} $. In particular, when $Δ\to\infty$ the model becomes dynamically constrained and most states are localized. We show, microscopically, existence of magnon bound states in the strong coupling regime, which behave as self-generated disorders for single magnons. Based on this quasiparticle picture, we obtain analytical scalings, which match well with the numerical results.

cond-mat.str-el↗

arXiv2019

Ground states of long-range interacting fermions in one spatial dimension

We explore systematically the ground state properties of one dimensional fermions with long-range interactions decaying in a power law $\sim1/r^α$ through the density matrix renormalization group algorithm. By comparing values of Luttinger liquid parameters precisely measured in two different ways, we show convincing evidence that Luttinger liquid theory is valid if $α$ is larger than some threshold, otherwise the theory breakdown. Combining analysis on structure factor, charge gap and charge stiffness, we determine how the metal-insulator transition point develops as the interaction range is continuously tuned. A region in the range of $0\leqα\leq1$ and small interactions has finite charge gaps, but, interestingly, it shows metallic nature at the same time. From these, we obtain approximate phase diagrams for the entire parameter space and for band fillings equal 1/2 and 1/3. Finally, we compare certain bosonization and field theory formula with our quasi-exact numerical results, from which disagreements are found.

cond-mat.str-el↗

arXiv2015

Matrix product state approach to a frustrated spin chain with long-range interactions

We make extensive simulations over a spin chain model that combines the frustrated $J_1\textrm{-}J_2$ spin chain and the long-range nonfrustrated $(-1)^{(r-1)}r^{-α}$ decay interactions through the variational matrix product state method for both finite and infinite lengths. We study both the ground state entanglement and phase diagram. We find that it is most entangled in the rotation invariant long-range ordered antiferromagnetic phase, where the entanglement scales approximately logarithmically. We determine the development of the Majudar-Ghosh point to a disorder line from entanglement. And we determine approximately the transition from the dimerized and incommensurate phase of the $J_1\textrm{-}J_2$ model to a decoupled phase by studying spin correlation and the dimerization order parameter. Some implications for entanglement in systems with long-range interactions are stated.

cond-mat.str-el↗

arXiv2013

Entanglement entropy in quasi-symmetric multi-qubit states

We generalize the symmetric multi-qubit states to their q-analogs, whose basis vectors are identified with the q-Dicke states. We study the entanglement entropy in these states and find that entanglement is extruded towards certain regions of the system due to the inhomogeneity aroused by q-deformation. We also calculate entanglement entropy in ground states of a related q-deformed Lipkin-Meshkov-Glick model and show that the singularities of entanglement can correctly signify the quantum phase transition points for different strengths of q-deformation.

quant-ph↗