Versatile tunable optical injection of chiral polarized Weyl fermions in a magnetic Weyl semimetal Co3Sn2S2

TL;DR

This paper demonstrates tunable optical control of chiral polarized Weyl fermions in a magnetic Weyl semimetal, enabling potential applications in mid-infrared photodetection and quantum devices exploiting chiral degrees of freedom.

Contribution

It reveals a versatile, tunable method to control chiral Weyl fermions using light, magnetic fields, and electric fields in a magnetic Weyl semimetal.

Findings

Observation of light chirality-dependent photocurrent.

Identification of a third-order nonlinear photocurrent process.

Enhanced tunability in magnetic Weyl semimetals compared to nonmagnetic ones.

Abstract

Precise probe and control of various quantum degrees of freedom in novel quantum matter are central to understanding fundamental quantum physics and hold promise for innovative routes to encode and process information. Chirality is one such degree of freedom that has recently attracted intense research interest, especially for Weyl fermions in topological Weyl semimetals. The coupling of chiral degrees of freedom through light-matter interactions and the versatile control of these couplings through external fields can lead to precise quantum control of Weyl fermions. In this work, we demonstrate the observation of light chirality-dependent photocurrent in the mid-infrared regime. Excitation wavelength-dependent measurements reveal that the photocurrent originates from the injection of chiral polarized Weyl fermions by chiral polarized mid-infrared photons. The optical process that generates unbalanced chiral polarized Weyl fermions is determined to be a third-order nonlinear photocurrent process. Compared with nonmagnetic Weyl semimetals, such coupling is versatilely tunable in magnetic Weyl semimetals with the magnetization direction and external electric field in addition to the chirality of light. Our results are not only directly applicable to tunable circular-polarization-sensitive photodetection in the mid-infrared regime, but also pave the way toward functional quantum devices that utilize the chiral quantum degrees of freedom of Weyl fermions.