Abstract
Intrinsic anomalous Nernst effect, like its Hall counterpart, is generated by Berry curvature of electrons in solids. Little is known about its response to disorder. In contrast, the link between the amplitude of the ordinary Nernst coefficient and the mean-free path is extensively documented. Here, by studying , a topological half-metallic semimetal hosting sizable and recognizable ordinary and anomalous Nernst responses, we demonstrate an anticorrelation between the amplitudes of carrier mobility and the anomalous (the ratio of transverse electric field to the longitudinal temperature gradient in the absence of magnetic field). We argue that the observation, paradoxically, establishes the intrinsic origin of the anomalous Nernst effect in this system. We conclude that various intrinsic off-diagonal coefficients are set by the way the Berry curvature is averaged on a grid involving the mean-free path, the Fermi wavelength, and the de Broglie thermal length.
- Received 11 July 2019
- Revised 22 October 2019
DOI:https://doi.org/10.1103/PhysRevX.9.041061
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
In the presence of a magnetic field and a thermal gradient, electrons in a solid, drifting from the hot side towards the cold side, generate a transverse voltage. This is the Nernst effect. In magnetic solids, a similar voltage can occur even in the absence of magnetic field, a phenomenon known as the anomalous Nernst effect. Researchers have not yet addressed the role that disorder might play in this context. Here, we experimentally demonstrate that in a half-metallic semimetal, the anomalous Nernst effect is proportional to the inverse of the carrier mobility, and we argue that this is compatible with a picture where the nontrivial topology of electrons in the host solid generates the anomalous Nernst effect.
For our experiments, we grow and study samples of , a material in which previous studies have documented a large anomalous Nernst effect. We quantify the carrier density and the mobility of charge carriers by measuring the magnetoresistance (the dependence of electrical resistance on an external magnetic field) and the ordinary Hall effect (a transverse voltage induced by a magnetic field). We find that increased mobility enhances the ordinary Nernst effect, but reduces the anomalous Nernst effect.
Our results provide new insights into the response of electrons with nontrivial topology to a thermal gradient.
