Dynamical Topological Quantum Phase Transitions at Criticality

TL;DR

This paper explores how dynamical quantum phase transitions in a 2D topological model are driven by massless quasiparticles, linking nonequilibrium dynamics with topological properties and revealing signatures in the Loschmidt amplitude.

Contribution

It demonstrates the role of massless quasiparticles in dynamical quantum phase transitions and verifies the topological nature of these transitions through quantized order parameters.

Findings

Massless quasiparticles cause nonanalytic signatures in Loschmidt amplitude.

Topological order parameter quantizes to even integers during DQPT.

Dynamical topological order captures phase transitions at zero Berry curvature line.

Abstract

The nonequilibrium dynamics of two dimensional Su-Schrieffer-Heeger model, in the presence of staggered chemical potential, is investigated using the notion of dynamical quantum phase transition. We contribute to expanding the systematic understanding of the interrelation between the equilibrium quantum phase transition and the dynamical quantum phase transition (DQPT). Specifically, we find that dynamical quantum phase transition relies on the existence of massless {\it propagating quasiparticles} as signaled by their impact on the Loschmidt overlap. These massless excitations are a subset of all gapless modes, which leads to quantum phase transitions. The underlying two dimensional model reveals gapless modes, which do not couple to the dynamical quantum phase transitions, while relevant massless quasiparticles present periodic nonanalytic signatures on the Loschmidt amplitude. The topological nature of DQPT is verified by the quantized integer values of the topological order parameter, which gets even values. Moreover, we have shown that the dynamical topolocical order parameter truly captures the topological phase transition on the zero Berry curvature line, where the Chern number is zero and the two dimensional Zak phase is not the proper idicator.