Giant Anomalous Ettingshausen Effect and Hybrid Longitudinal-Transverse Thermoelectric Cooling in a Nanoscale Magnetic Weyl Semimetal.

Abstract

Solid-state cooling devices offer compact, quiet, reliable and environment-friendly solutions that currently rely on conventional thermoelectric (TE) effects. Despite more than two centuries of research, classical thermoelectric coolers suffer from low efficiency which hampers wider application. In this study, a combination of the less researched Anomalous Ettingshausen effect (AEE), a transverse thermoelectric phenomenon, and a geometrically induced Peltier effect is presented as an approach for on-chip cooling. The anomalous Ettingshausen effect can be boosted in materials with nontrivial band topologies as demonstrated in the Heusler alloy Co₂MnGa. Enabled by the high quality of our material, in situ scanning thermal microscopy experiments reveal a giant anomalous Ettingshausen coefficient of 3.1 mV in μm-sized on-chip cooling devices at room temperature. A significant 57% of the effect is contributed by the intrinsic topological properties, in particular the Berry curvature of Co₂MnGa. We then demonstrate that a geometrical Peltier effect can be induced in the films by fabricating nanoribbon devices which increases the figure of merit by 170%. The combined cooling action of the anomalous Ettingshausen and the Peltier effect yield a nm-sized local spot cooler emphasizing the potential of nanostructured magnetic Weyl semimetals.