Many-body Keldysh Crossover in the DC-driven Haldane Spin Chain

TL;DR

This paper investigates how a DC electric field influences the topological order and spin transport in a Haldane spin chain, revealing a crossover between tunneling and symmetry-breaking mechanisms.

Contribution

It introduces a detailed analysis of the many-body Keldysh crossover in a quantum spin system driven by a DC field, combining numerical and theoretical approaches.

Findings

Finite spin current and accumulation induced by the field

Identification of two microscopic mechanisms for breakdown

Verification of the universal Keldysh crossover picture

Abstract

We theoretically study nonlinear processes driven by a DC spin-electric field in the antiferromagnetic spin-1 Heisenberg model starting from the ground state in the Haldane phase. The DC spin-electric field generates finite spin current and accumulation since the symmetry protected topological order is destroyed by the field. We find two microscopic mechanisms responsible for the breakdown and a crossover between them: In weak fields, tripron-antitripron pair creation occurs through the tunneling mechanism, and in strong fields, the system is described by an effective Hamiltonian breaking the protecting symmetries. We analyze the numerically obtained results in terms of the Dykhne--Davis--Pechukas theory and Floquet theory, verifying the universal picture of the many-body Keldysh crossover in the DC-driven quantum spin systems.