Thickness dependent tuning of the Berry curvature in a ferromagnetic Weyl semimetal

TL;DR

This study demonstrates that the Berry curvature and anomalous Hall effect in ferromagnetic Weyl semimetal Co2MnGa thin films depend strongly on thickness, impacting their potential for room-temperature topo-spintronics.

Contribution

It reveals the thickness-dependent tuning of Berry curvature and anomalous Hall effect in Co2MnGa thin films, highlighting the importance of film thickness in device applications.

Findings

Large anomalous Hall angle (~11.4%) at low temperature

Significant decrease in Hall angle below 20 nm thickness

Band structure calculations confirm reduction of Berry curvature with decreasing thickness

Abstract

Magnetic Weyl semimetals with spontaneously broken time-reversal symmetry exhibit a large intrinsic anomalous Hall effect originating from the Berry curvature. To employ this large Hall current for room temperature topo-spintronics applications, it is necessary to fabricate these materials as thin or ultrathin films. Here, we experimentally demonstrate that Weyl semimetal Co2MnGa thin films (20-50 nm) show a very large anomalous Hall angle ~11.4% at low temperature and ~9.7% at room temperature, which can be ascribed to the nontrivial topology of the band structure with large intrinsic Berry curvature. However, the anomalous Hall angle decreases significantly with thicknesses below 20 nm, which band structure calculations confirm is due to the reduction of the majority spin contribution to the Berry curvature. Our results suggest that Co2MnGa is an excellent material to realize room temperature topo-spintronics applications, however the significant thickness dependence of the Berry curvature has important implications for thin film device design