Persistent spin currents in mesoscopic Heisenberg rings

TL;DR

This paper predicts that a mesoscopic ferromagnetic Heisenberg ring subjected to an inhomogeneous radial magnetic field can sustain a persistent spin current at low temperatures, which induces an electric dipole moment.

Contribution

It introduces the concept of persistent spin currents in mesoscopic Heisenberg rings driven by inhomogeneous magnetic fields, with quantitative estimates from spin-wave theory.

Findings

Persistent spin currents can be generated at low temperatures.

The magnitude of the spin current depends exponentially on magnetic field and energy gap.

The induced spin current creates an electric dipole moment in the ring.

Abstract

We show that at low temperatures T an inhomogeneous radial magnetic field with magnitude B gives rise to a persistent magnetization current around a mesoscopic ferromagnetic Heisenberg ring. Under optimal conditions this spin current can be as large as g mu_B (T / hbar) exp [ - 2 pi (g mu_B B / Delta )^1/2 ], as obtained from leading-order spin-wave theory. Here g is the gyromagnetic factor, mu_B is the Bohr magneton, and Delta is the energy gap between the ground state and the first spin-wave excitation. The magnetization current endows the ring with an electric dipole moment.