Anomalous Hall Effect induced by extremely low field in ZrTe₅

ZrTe₅ has gathered interest in recent years due to its non-trivial topology. In monolayer form, it is predicted to be a quantum spin hall insulator. In bulk, it is predicted to reside extremely close to a phase transition between a strong and weak topological insulator. We report detailed measurements of the anomalous hall effect (AHE) in ZrTe₅. We find the hall resistance saturates at an extremely low magnetic field ( B << 1T ), and remains at the saturation value for fields up to 32T. This AHE is present despite no evidence of magnetism in ZrTe₅. Furthermore, in exfoliated devices in a quasi-bulk regime (dozens of layers thick) we find that the low-field orbital hall effect is suppressed and the AHE is clearly seen. We investigate the AHE effect in ZrTe5 as a function of temperature, magnetic field angle, and doping, and discuss the potential origins of this effect related to a non-vanishing berry curvature.