Predicting Critical Phases from Entanglement Dynamics in XXZ Alternating Chain

TL;DR

This paper demonstrates how entanglement dynamics in the XXZ alternating chain can detect quantum phase transitions and critical phases, offering insights into quantum information applications and phase characterization.

Contribution

It introduces entanglement-based methods to identify quantum critical points and phases in the XXZ alternating chain, including dynamical detection of phase transitions.

Findings

Multipartite entanglement signals quantum critical lines.

Nonanalytic behavior of entanglement indicates phase transitions.

Block entanglement entropy patterns reveal equilibrium phases.

Abstract

The quantum XXZ spin model with alternating bond strengths under magnetic field has a rich equilibrium phase diagram which includes Haldane, Luttinger liquid, singlet, and paramagnetic phases. We show that the nearest neighbor bipartite and multipartite entanglement can detect quantum critical lines and phases in this model. We determine a region in parameter space in which the dynamical states, starting from the ground state of the Haldane (dimer) phase can create highly multipartite entangled states for any time period, thereby establishing it as a potential candidate for the implementation of quantum information tasks. We also exhibit that if the initial and evolved states are in two different phases, the nonanalytic behavior of multipartite entanglement and the rate function based on Loschmidt echo can signal quantum phase transition happened at zero temperature. In a similar spirit, we report that from the product state, the patterns of block entanglement entropy of the evolved state with time can also infer the phase transition at equilibrium.