Phase diagram and post-quench dynamics in a double spin-chain system in transverse fields

TL;DR

This paper investigates a coupled double spin-chain model with transverse fields, analyzing its phase diagram and post-quench dynamics, revealing coupled oscillations, energy transfer, and fast spin-wave modes relevant for quantum information transfer.

Contribution

It introduces a novel multiferroic toy model coupling two XXZ chains, exploring its phase diagram and dynamic behavior after quenches using advanced numerical methods.

Findings

Decaying coupled oscillations consistent with ETH.

Quadratic shift in oscillation frequency with inter-chain coupling.

Light-cone-like propagation and a fast spin-wave mode.

Abstract

We propose and explore the physics of a toy multiferroic model by coupling two distinct dipolar XXZ models in transverse fields. We determine first the rich ground-state phase diagram of the model using density matrix renormalization group techniques. Then, we explore the dynamics of the system after global and local quenches, using the time-evolving block decimation algorithm. After a global quench, the system displays decaying coupled oscillations of the electric and magnetic spins, in agreement with the Eigenstate Thermalization Hypothesis (ETH) for many-body interacting quantum systems. Notably, the spin-spin interactions lead to a sizeable quadratic shift in the oscillation frequency as the inter-chain coupling is increased. Local quenches lead to a light-cone-like propagation of excitations. In this case, the inter-chain coupling drives a transfer of energy between the chains that generates a novel fast spin-wave mode along the 'magnetic' chain at the speed of the 'electric' spin-wave. This suggests a limited control mechanism for faster information transfer in magnetic spin chains using electric fields that harnesses the electric dipoles as intermediaries.