Driving XXZ spin chains: Magnetic-field and boundary effects

TL;DR

This paper investigates how magnetic fields and boundary conditions influence spin transport in XXZ spin chains, revealing resonance phenomena, fixed points, and edge state effects using advanced numerical methods.

Contribution

It introduces a detailed analysis of spin transport in XXZ chains under magnetic fields and boundary effects, highlighting fixed points and Kondo physics in the Haldane phase.

Findings

Resonances in spin conductance as a function of magnetic field.

Identification of a conducting fixed point in spin-1/2 chains.

Edge states induce two-impurity Kondo physics in the Haldane phase.

Abstract

Using the time-evolving block decimation, we study the spin transport through spin-1/2 and spin-1 XXZ chains subjected to an external magnetic field and contacted to noninteracting fermionic leads. For generic system-lead couplings, the spin conductance exhibits several resonances as a function of the magnetic-field strength. In the spin-1/2 but not the spin-1 case, the coupling to the leads can be fine-tuned to reach a conducting fixed point, where the peak structure is washed out and the spin conductance is large throughout the gapless Luttinger-liquid phase. For the Haldane phase of the spin-1 chain, we analyse how the spin transport is affected by spin-1/2 edge states, and argue that two-impurity Kondo physics is realised.