Widely Tunable Berry curvature in the Magnetic Semimetal Cr1+dTe2

TL;DR

This study investigates how doping in Cr1+dTe2 thin films tunes the Berry curvature and anomalous Hall effect, revealing a sign change linked to the crossing of a semi-metallic band through the Fermi level, highlighting the material's topological potential.

Contribution

It provides the first systematic analysis of doping-dependent Berry curvature and anomalous Hall effect in Cr1+dTe2, connecting experimental observations with theoretical calculations.

Findings

Doping causes a rigid band shift near the Brillouin Zone edge.

The anomalous Hall effect sign flips as doping varies.

Berry curvature sign change drives the AHE sign flip.

Abstract

Magnetic semimetals have increasingly emerged as lucrative platforms hosting spin-based topological phenomena in real and momentum spaces. Of particular interest is the emergence of Berry curvature, whose geometric origin, accessibility from Hall transport experiments, and material tunability, bodes well for new physics and practical devices. Cr1+dTe2, a self-intercalated magnetic transition metal dichalcogenide, TMD, exhibits attractive natural attributes relevant to such applications, including topological magnetism, tunable electron filling, magnetic frustration etc. While recent studies have explored real-space Berry curvature effects in this material, similar considerations of momentum-space Berry curvature are lacking. Here, we systematically investigate the electronic structure and transport properties of epitaxial Cr1+dTe2 thin films over a wide range of doping, d between 0.33 and 0.71. Spectroscopic experiments reveal the presence of a characteristic semi-metallic band region near the Brillouin Zone edge, which shows a rigid band like energy shift as a function of d. Transport experiments show that the intrinsic component of the anomalous Hall effect, AHE, is sizable, and undergoes a sign flip across d. Finally, density functional theory calculations establish a causal link between the observed doping evolution of the band structure and AHE: the AHE sign flip is shown to emerge from the sign change of the Berry curvature, as the semi-metallic band region crosses the Fermi energy. Our findings underscore the increasing relevance of momentum-space Berry curvature in magnetic TMDs and provide a unique platform for intertwining topological physics in real and momentum spaces.