arXiv subjects

Ze-Xun Lin

Publications and source records attributed to Ze-Xun Lin.

8 recordsLinked to original sources

arXiv2025

Chiral Cavity Control of the Interlayer Exciton Energy Spectrum

Heterostructures of two-dimensional materials offer a versatile platform to study light-matter interactions of electron and hole gases. By separating electron and hole layers with an insulator long-lived electron-hole bound states known as interlayer excitons can form. We predict that by placing an interlayer exciton in a time-reversal-symmetry-breaking chiral cavity the energy spectrum of an interlayer exciton can be reordered. As a consequence of this reordering the ground state of the interlayer exciton can be driven from an s-orbital to a p-orbital, effectively changing the symmetry of the electron-hole pair. We present a phase diagram showing the couplings and separations required for a p-orbital excitonic ground state where we predict that larger interlayer separations require higher cavity couplings. We expect these results to be relevant for angular-momentum-tunable, single photon emission physics.

cond-mat.str-el↗

arXiv2025

Hamiltonian Learning at Heisenberg Limit for Hybrid Quantum Systems

Hybrid quantum systems with different particle species are fundamental in quantum materials and quantum information science. In this work, we establish a rigorous theoretical framework proving that, given access to an unknown spin-boson type Hamiltonian, our algorithm achieves Heisenberg-limited estimation for all coupling parameters up to error $\epsilon$ with a total evolution time ${O}(\epsilon^{-1})$ using only ${O}({\rm polylog}(\epsilon^{-1}))$ measurements. It is also robust against small state preparation and measurement errors. In addition, we provide an alternative algorithm based on distributed quantum sensing, which significantly reduces the evolution time per measurement. To validate our method, we demonstrate its efficiency in hybrid Hamiltonian learning and spectrum learning, with broad applications in AMO, condensed matter and high energy physics. Our results provide a scalable and robust framework for precision Hamiltonian characterization in hybrid quantum platforms.

quant-ph↗

arXiv2024

Interlayer Dzyaloshinskii-Moriya interactions induced via non-linear phononics in bilayer van der Waals materials

We theoretically study the impact of light-driven structural changes via nonlinear phononics on the magnetic order of untwisted bilayer van der Waals materials. We consider an illustrative example of the AA-stacked bilayer honeycomb lattice and show that high-intensity light in resonance with selected phonons induces large amplitude phonon displacements that modify the magnetic Hamiltonian of the system. We performed a group theory analysis to identify the vibrational modes of the honeycomb bilayer and the nonlinear couplings among them in the strongly driven regime. We find that the structural changes in the strongly driven regime lower the symmetry relative to the equilibrium lattice and produce changes in the magnetic interactions between the local moments. In particular, the lattice symmetry changes permit a non-zero interlayer Dzyaloshinskii-Moriya interaction that induces a magnetic state with canted local moments. Using a spin-wave analysis about the new magnetic configuration we study the corresponding changes in the magnon spectrum and identify a protocol for engineering topological band transitions using a combination of nonlinear phononics and an external magnetic field. Our work suggests a strategy to induce and control interlayer Dyzaloshinskii-Moriya interactions in a class of layered van der Waals materials, the effect of which is to modify the magnetic ground state, magnon dispersions, and related band geometric properties, including topological invariants.

cond-mat.str-el↗

arXiv2021

Fate of entanglement in one-dimensional fermion liquid with coherent particle loss

Quantum many-body systems and quantum devices experience the detrimental effects of noise and particle losses, necessitating their treatment as open quantum systems or, in approximation, as non-Hermitian systems. These systems exhibit nontrivial characteristics in their time evolution that differ significantly from closed systems. In this Letter, we study the dynamic properties of a one-dimensional fermionic system with adjacent-lattice particle loss. By utilizing time-dependent correlation matrix methods and bosonization techniques, we demonstrate that, as the system evolves over time, its (bipartite) von Neumann entropy exhibits a universal behavior of rapid increase due to thermalization effects at short times, independent of the effective Hamiltonian and Liouvillian spectra, even in the presence of interactions. Additionally, we show that the asymmetric non-Hermitian terms in the effective Hamiltonian caused by adjacent-lattice quantum jumps lead to left-right asymmetry of quasiparticles in momentum space, which is ubiquitous in non-Hermitian skin effects and introduces momentum-space entanglement independent of the interaction strength at early times. Our study illuminates the universal fate of non-Hermitian fermionic liquids in the open quantum context, enriching our understanding of non-Hermitian many-body systems over the entire time range. Furthermore, our findings provide valuable insights for near-term quantum devices and the quantum simulation of open systems.

quant-ph↗

arXiv2021

Real-time simulation of light-driven spin chains on quantum computers

In this work, we study the real-time evolution of periodically driven (Floquet) systems on a quantum computer using IBM quantum devices. We consider a driven Landau-Zener model and compute the transition probability between the Floquet steady states as a function of time. We find that for this simple one-qubit model, Floquet states can develop in real-time, as indicated by the transition probability between Floquet states. Next, we model light-driven spin chains and compute the time-dependent antiferromagnetic order parameter. We consider models arising from light coupling to the underlying electrons as well as those arising from light coupling to phonons. For the two-spin chains, the quantum devices yield time evolutions that match the effective Floquet Hamiltonian evolution for both models once readout error mitigation is included. For three-spin chains, zero-noise extrapolation yields a time dependence that follows the effective Floquet time evolution. Therefore, the current IBM quantum devices can provide information on the dynamics of small Floquet systems arising from light drives once error mitigation procedures are implemented.

cond-mat.mes-hall↗

arXiv2021

Light-driven topological and magnetic phase transitions in thin-layer antiferromagnets

We theoretically study the effect of low-frequency light pulses in resonance with phonons in the topological and magnetically ordered two septuple-layer (2-SL) MnBi2Te4 (MBT) and MnSb2Te4 (MST). These materials share symmetry properties and an antiferromagnetic ground state in pristine form but present different magnetic exchange interactions. In both materials, shear and breathing Raman phonons can be excited via non-linear interactions with photo-excited infrared phonons using intense laser pulses attainable in current experimental setups. The light-induced transient lattice distortions lead to a change in the sign of the effective interlayer exchange interaction and magnetic order accompanied by a topological band transition. Furthermore, we show that moderate anti-site disorder, typically present in MBT and MST samples, can facilitate such an effect. Therefore, our work establishes 2-SL MBT and MST as candidate platforms to achieve non-equilibrium magneto-topological phase transitions.

cond-mat.mes-hall↗

arXiv2020

Phonon-mediated dimensional crossover in bilayer CrI3

In bilayer CrI3, experimental and theoretical studies suggest that the magnetic order is closely related to the layer staking configuration. In this work, we study the effect of dynamical lattice distortions, induced by non-linear phonon coupling, in the magnetic order of the bilayer system. We use density functional theory to determine the phonon properties and group theory to obtain the allowed phonon-phonon interactions. We find that the bilayer structure possesses low-frequency Raman modes that can be non-linearly activated upon the coherent photo-excitation of a suitable infrared phonon mode. This transient lattice modification, in turn, inverts the sign of the interlayer spin interaction for parameters accessible in experiments, indicating a low-frequency light-induced antiferromagnet-to-ferromagnet transition.

cond-mat.mes-hall↗

arXiv2018

Chiral supercurrent through a quantum Hall weak link

We use a microscopic model to calculate properties of the supercurrent carried by chiral edge states of a quantum Hall weak link. This "chiral" supercurrent is qualitatively distinct from the usual Josephson supercurrent in that it cannot be mediated by a single edge alone, i.e., both right and left going edges are needed. Moreover, chiral supercurrent was previously shown to obey an unusual current-phase relation with period $2 \phi_0=h/e$, which is twice as large as the period of conventional Josephson junctions. We show that the "chiral" nature of this supercurrent is sharply defined, and is robust to interactions to infinite order in perturbation theory. We compare our results with recent experimental findings of Amet et al [Science, 352(6288)] and find that quantitative agreement in magnitude of the supercurrent can be attained by making reasonable but critical assumptions about the superconductor quantum Hall interface.

cond-mat.mes-hall↗