Persistent spin currents in mesoscopic Haldane gap spin rings

TL;DR

This paper demonstrates that mesoscopic Haldane gap spin rings can sustain persistent circulating spin currents under inhomogeneous fields, with quantum fluctuations influencing the current's magnitude and decay.

Contribution

It introduces a modified spin-wave approach to show persistent spin currents in Haldane gap systems under inhomogeneous fields, highlighting quantum fluctuation effects.

Findings

Persistent spin currents occur in mesoscopic Haldane gap rings with inhomogeneous fields.

Quantum fluctuations limit the current to a finite value at zero temperature.

The current is exponentially suppressed when the correlation length is much smaller than the ring circumference.

Abstract

Using a modified spin-wave approach, we show that in the presence of an inhomogeneous magnetic field or an in plane inhomogeneous electric field a mesoscopic antiferromagnetic Heisenberg ring with integer spin (i.e., a Haldane gap system) exhibits a persistent circulating spin current. Due to quantum fluctuations the current has a finite limit on the order of -g mu_B c/L at zero temperature, provided the staggered correlation length xi exceeds the circumference L of the ring, in close analogy to ballistic charge currents in mesoscopic normal metal rings. Here c is the spin-wave velocity, g is the gyromagnetic ratio and mu_B is the Bohr magneton. For xi<<L the current is exponentially suppressed.