arXiv subjects

Yuxiao Hang

Publications and source records attributed to Yuxiao Hang.

5 recordsLinked to original sources

arXiv2026

Many-Body Protection of Topological Edge Memory in Strong Interacting Quenches

Quantum quenches drive edge states far from equilibrium, yet whether the memory of a topological initial state survives in a non-integrable, interacting system has remained largely unexplored. We study this question in the bond-alternating XXZ chain---an interacting Su--Schrieffer--Heeger model hosting symmetry-protected topological edge modes with markedly enhanced boundary magnetization---and analyze quenches across all combinations of single-particle and many-body initial and final Hamiltonians. The results organize by a single distinction as we rigorously establish in this work: whether the post-quench Hamiltonian is free or genuinely interacting. For a free post-quench Hamiltonian, the dynamics is solved exactly by a correlation-matrix approach; the boundary-mode return amplitude decays as $t^{-3/2}$, and initial interactions enter only through a dressed one-body density matrix. For a genuinely interacting post-quench Hamiltonian, finite-time stability bounds prove that away from local resonances the first-dimer magnetization remains stable on time windows growing as arbitrarily large powers of the inverse inter-dimer coupling. Matrix product state simulations across all four protocols show that interactions in the final Hamiltonian markedly extend finite-time boundary memory---with local suppression near the isotropic $SU(2)$ point---revealing a many-body protection mechanism in a non-integrable system where scrambling would otherwise wash out initial-state memory fast.

cond-mat.str-el↗

arXiv2026

Dynamics of Majorana Fermions on a Quantum Computer

The study of quasiparticle dynamics is central to understanding non-equilibrium phenomena in quantum many-body systems. Direct simulation of such dynamics on quantum hardware has been limited by circuit depth and noise constraints. In this work, we use a recently developed constant-depth circuit algorithm to examine the real-time evolution of site-resolved magnetization in a transverse-field Ising chain on noisy intermediate-scale quantum devices. By representing each spin as a pair of Majorana fermions, we identify two distinct dynamical regimes governed by the relative strength of spin interaction. Furthermore, we show how local impurities can serve as probes of Majorana modes, acting as dynamical barriers in the weak coupling regime. These results demonstrate that constant-depth quantum circuits provide a viable route for studying quasiparticle propagation and for probing Majorana signatures on currently available quantum processors.

cond-mat.str-el↗

arXiv2025

Topological Phase Diagram of Generalized SSH Models with Interactions

We investigate interacting Su-Schrieffer-Heeger (SSH) chains with two- and three-site unit cells using density matrix renormalization group (DMRG) simulations. By selecting appropriate filling fractions and sweeping across interaction strength $ J_z $ and dimerization $ δ$, we map out their phase diagrams and identify transition lines via entanglement entropy and magnetization measurements. In the two-site model, we observe the emergence of an interaction-induced antiferromagnetic intermediate phase between the topologically trivial and non-trivial regimes, as well as a critical region at negative $ J_z $ with suppressed magnetization and finite-size scaling of entanglement entropy. In contrast, the three-site model lacks an intermediate phase and exhibits asymmetric edge localization and antiferromagnetic ordering in both positive and negative $ J_z $ regimes. We further examine the response of edge states to Ising perturbations. In the two-site model, zero-energy edge modes are topologically protected and remain robust up to a finite interaction strength. However, in the three-site model, where the edge states reside at finite energy, this protection breaks down. Despite this, the edge-localized nature of these states survives in the form of polarized modes whose spatial profiles reflect the non-interacting limit.

cond-mat.str-el↗

arXiv2024

Entanglement flow in the Kane-Fisher quantum impurity problem

The problem of a local impurity in a Luttinger liquid, just like the anisotropic Kondo problem (of which it is technically a cousin), describes many different physical systems. As shown by Kane and Fisher, the presence of interactions profoundly modifies the physics familiar from Fermi liquid theory, and leads to non-intuitive features, best described in the Renormalization Group language (RG), such as flows towards healed or split fixed points. While this problem has been studied for many years using more traditional condensed matter approaches, it remains somewhat mysterious from the point of view of entanglement, both for technical and conceptual reasons. We propose and explore in this paper a new way to think of this important aspect. We use the realization of the Kane Fisher universality class provided by an XXZ spin chain with a modified bond strength between two sites and explore the difference of (Von Neumann) entanglement entropies of a region of length $\ell$ with the rest of the system - to which it relates to a modified bond - in the cases when $\ell$ is even and odd. Surprisingly, we find out that this difference $δS\equiv S^e-S^o$ remains of $O(1)$ in the thermodynamic limit, and gives rise now, depending on the sign of the interactions, to "resonance" curves, interpolating between $-\ln 2$ and $0$, and depending on the product $\ell T_B$, where $1/T_B$ is a characteristic length scale akin to the Kondo length in Kondo problems. $δS$ can be interpreted as a measure of the hybridization of the left-over spin in odd length subsystems with the "bath" constituted by the rest of the chain. The problem is studied both numerically using DMRG and analytically near the healed and split fixed points. Interestingly - and in contrast with what happens in other impurity problems - $δS$ can, at least to lowest order, be tackled by conformal perturbation theory.

cond-mat.str-el↗

arXiv2021

Electron-electron double resonance detected NMR spectroscopy using ensemble NV centers at 230 GHz and 8.3 Tesla

The nitrogen-vacancy (NV) center has enabled widespread study of nanoscale nuclear magnetic resonance (NMR) spectroscopy at low magnetic fields. NMR spectroscopy at high magnetic fields significantly improves the technique's spectral resolution, enabling clear identification of closely related chemical species. However, NV-detected NMR is typically performed using AC sensing through electron spin echo envelope modulation (ESEEM), a hyperfine spectroscopic technique that is not feasible at high magnetic fields. Within this paper, we have explored an NV-detected NMR technique for applications of high field NMR. We have demonstrated optically detected magnetic resonance (ODMR) with the NV Larmor frequency of 230 GHz at 8.3 Tesla, corresponding to a proton NMR frequency of 350 MHz. We also demonstrated the first measurement of electron-electron double resonance detected NMR (EDNMR) using the NV center and successfully detected $^{13}C$ nuclear bath spins. The described technique is limited by the longitudinal relaxation time ($T_1$), not the transverse relaxation time ($T_2$). Future applications of the method to perform nanoscale NMR of external spins at 8.3 T and even higher magnetic fields are also discussed.

cond-mat.mes-hall↗