Spin Transport Properties in Heisenberg Antiferromagnetic Spin Chains: Spin Current induced by Twisted Boundary Magnetic Fields

TL;DR

This paper investigates spin transport in one-dimensional Heisenberg antiferromagnetic chains with different spins, revealing distinct behaviors for S=1/2 and S=1, including a proposed London equation and exponential decay of spin current.

Contribution

It introduces a comparative analysis of spin transport in S=1/2 and S=1 chains under twisted boundary magnetic fields, highlighting new theoretical insights and behaviors.

Findings

Spin-half chains follow a London equation for spin current.

Spin-one chains exhibit exponential decay of spin current with chain length.

Midgap states emerge from degenerate ground states even at small boundary fields.

Abstract

Spin transport properties of the one-dimensional Heisenberg antiferromagnetic spin systems for both $S=1/2$ and S=1 are studied by applying twisted boundary magnetic field. The spin current displays significantly different behavior of the spin transport properties between $S=1/2$ and S=1 cases. For the spin-half case, a London equation for the current and the detection of an alternating electric field are proposed for the linear response regime. The correlation functions reveal the spiral nature of spin configuration for both ground state and the spinon excitations. For the spin-one chain otherwise, a kink is generated in the ground state for the size is larger than the correlation length, leading to an exponential dependence of spin current with respect to the chains length. The midgap state emerges from the degenerate ground state even for small boundary fields.