# Probing and controlling spin chirality in Mott insulators by circularly polarized laser

## TL;DR

This paper demonstrates how circularly polarized laser can directly couple to and control scalar spin chirality in Mott insulators, using Floquet theory to derive an effective Hamiltonian.

## Contribution

It provides a systematic derivation showing the significant coupling of scalar spin chirality to circularly polarized light in a driven Hubbard model.

## Key findings

- Scalar spin chirality couples directly to circularly polarized laser.
- Coupling becomes significant when driving frequency and on-site interaction are comparable.
- Potential for inducing or probing chirality in Mott insulators using circular dichroism.

## Abstract

Scalar spin chirality, a three-body spin correlation that breaks time-reversal symmetry, is revealed to couple directly to circularly polarized laser. This is shown by the Floquet formalism for the periodically driven repulsive Hubbard model with a strong-coupling expansion. A systematic derivation of the effective low-energy Hamiltonian for a spin degree of freedom reveals that the coupling constant for scalar spin chirality can become significant for a situation in which the driving frequency and the on-site interaction are comparable. This implies that the scalar chirality can be induced by circularly polarized lights, or that it can be used conversely for probing the chirality in Mott insulators as a circular dichroism.