Generation of DC, AC, and Second-Harmonic Spin Currents by Electromagnetic Fields in an Inversion-Asymmetric Antiferromagnet

Tatsuhiko N Ikeda

doi:10.3390/condmat4040092

Abstract

Manipulating spin currents in magnetic insulators is a key technology in spintronics. We theoretically study a simple inversion-asymmetric model of quantum antiferromagnets, where both the exchange interaction and the magnetic field are staggered. We calculate spin currents generated by external electric and magnetic fields by using a quantum master equation. We show that an ac electric field with amplitude E 0 leads, through exchange-interaction modulation, to the dc and second-order harmonic spin currents proportional to E 0 2 . We also show that dc and ac staggered magnetic fields B 0 generate the dc and ac spin currents proportional to B 0 , respectively. We elucidate the mechanism by an exactly solvable model, and thereby propose the ways of spin current manipulation by electromagnetic fields.

Highlights

Spintronics has attracted growing attention in fundamental and applied physics for decades [1,2,3], where the researchers have explored how to manipulate the spin degree of freedom in materials and devices [4]
The spin Hall effect deriving from the spin-orbit coupling enables the conversion between the spin current and the electric current [5,6,7], and the spin Seebeck effect [8] extends to the research field of spin caloritronics [9]
We show that an ac electric field of amplitude E0 leads to exchange-interaction modulation [26] and gives rise to the dc and second-order harmonic spin currents whose magnitude are proportional to E02

Summary

Introduction

Spintronics has attracted growing attention in fundamental and applied physics for decades [1,2,3], where the researchers have explored how to manipulate the spin degree of freedom in materials and devices [4]. Ishizuka and Sato [23,24] theoretically showed that inversion-asymmetric antiferromagnets are useful for spin–current generation by electromagnetic waves. They proposed the spin–current rectification in ac electric and magnetic fields, where the magnitude of the generated dc spin current is proportional to the second power of the input-field amplitude. The dc spin–current generation as rectification has been numerically confirmed and the second-order harmonic spin current is studied in Ref. [25]

Methods

Results

Conclusion