THz range Faraday rotation in the Weyl Semimetal Candidate $\mathrm{Co_2TiGe}$

TL;DR

This study investigates the THz-range Faraday rotation in Co2TiGe thin films, revealing the influence of Weyl nodes and Berry curvature on transport properties, and highlighting their potential in spintronic applications.

Contribution

First measurement of THz Faraday rotation in Co2TiGe films, linking experimental results with electronic band structure calculations to demonstrate Weyl semimetal characteristics.

Findings

THz Faraday rotation observed in Co2TiGe films

Berry curvature significantly influences anomalous Hall effect

Potential for Weyl semimetal spintronics applications

Abstract

The $\mathrm{Co_2}$ family of ferromagnetic Heusler alloys have attracted interest due to their fully spin-polarized nature, making them ideal for applications in spintronic devices. More recently, the existence of room temperature time-reversal-breaking Weyl nodes near the Fermi level was predicted and confirmed in these systems. As a result of the presence of these Weyl nodes, these systems possess a non-zero momentum space Berry curvature that can dramatically influence transport properties such as the anomalous Hall effect. One of these candidate compounds is $\mathrm{Co_2 Ti Ge}$. Recently, high quality molecular beam epitaxy-grown thin films of $\mathrm{Co_2 Ti Ge}$ have become available. In this work, we present THz-range measurement of MBE-grown $\mathrm{Co_2 Ti Ge}$ films. We measure the THz-range Faraday rotation, which can be understood as a measure of the anomalous Hall effect. We supplement this work with electronic band structure calculations showing that the principal contribution to the anomalous Hall effect in the this material stems from the Berry curvature of the material. Our work shows that this class of Heusler materials shows promise for Weyl semimetal based spintronics.