Spin-chirality-driven second-harmonic generation in two-dimensional magnet CrSBr

TL;DR

This paper uncovers a novel, tunable second-harmonic generation mechanism in antiferromagnetic CrSBr bilayers driven by spin chirality, with potential applications in optical devices and magnetoelectric detection.

Contribution

It introduces chiral SHG driven by vector spin chirality in 2D antiferromagnetic materials, demonstrating tunability and interference effects not previously reported.

Findings

Chiral SHG can be tuned from zero to ten times larger than intrinsic MSHG.

Chiral SHG is proportional to spin chirality and electric polarization.

Interference between chiral and intrinsic MSHG causes giant SHG modulation.

Abstract

The interplay between magnetism and light can create abundant optical phenomena. Here, we demonstrate the emergence of an unconventional magnetization-induced second-harmonic generation (MSHG) stemming from vector spin chirality, denoted as chiral second-harmonic generation (SHG). Taking the antiferromagnetic (AFM) CrSBr bilayer as a prototype, we theoretically show that, via spin canting, the chiral SHG can be continuously tuned from zero to a value one order of magnitude larger than its intrinsic MSHG. Chiral SHG is found to be proportional to spin chirality and spin-canting-induced electric polarization, while intrinsic MSHG is proportional to the N\'eel vector, demonstrating their different physical mechanisms. Additionally, we reveal a unique interference effect between these two types of MSHG under the reversal of spin-canting direction, generating a giant modulation of SHG signals. Our work not only uncovers a unique SHG with exceptional tunability but also promotes the applications of AFM optical devices and magnetoelectric detection techniques.