Helicity-dependent Ultrafast Photocurrents in Weyl Magnet Mn$_3$Sn

TL;DR

This study demonstrates that Mn$_3$Sn, a non-collinear antiferromagnet, can generate controllable THz radiation through ultrafast photocurrents induced by femtosecond laser pulses, with emission characteristics dependent on optical polarization.

Contribution

It reveals the mechanism of THz emission in Mn$_3$Sn as photocurrents from the photon drag effect, supported by experimental and symmetry analysis, advancing understanding of ultrafast spintronic phenomena in antiferromagnets.

Findings

Mn$_3$Sn$$ emits THz radiation upon femtosecond laser excitation.

THz emission polarity and amplitude are controlled by optical polarization.

Photon drag effect explains the photocurrent generation mechanism.

Abstract

We present an optical pump-THz emission study on non-collinear antiferromagnet Mn$_3$Sn. We show that Mn$_3$Sn acts as a source of THz radiation when irradiated by femtosecond laser pulses. The polarity and amplitude of the emitted THz fields can be fully controlled by the polarisation of optical excitation. We explain the THz emission with the photocurrents generated via the photon drag effect by combining various experimental measurements as a function of pump polarisation, magnetic field, and sample orientation with thorough symmetry analysis of response tensors.