Skyrmion crystal as a promising thermoelectric converter: A prediction from first-principles
The anomalous Nernst effect (ANE), a heat-to-electric conversion in mutually transverse directions, can be driven by an emergent magnetic field B originating from inhomogeneous magnetic moments in solids. Large ANE has been experimentally confirmed in various ferromagnets, and only very recently, also in an antiferromagnet . Here we theoretically propose that, the Skyrmion crystal (SkX), in which magnetic topological objects Skyrmions are crystallized, is another candidate to host large ANE.
We have found through first-principles calculations on a single s-orbital model using the package OpenMX  and Wannier90  that, in a two dimensional SkX phase a large ANE would appear when chemical potential μ is properly tuned (Figure) . This was interpreted as due to its characteristic distribution of Chern numbers among the bands (each Chern number representing quantized flux of B field through each electronic band in momentum space).
Following such an observation in the simplest model of square SkX , our subsequent computations on a more realistic oxide film also predict large ANE.
This motivates further studies of ANE in the SkX family, in quest of better thermoelectric materials that exploit this effect.
 M. Ikhlas et al., Nature Physics (2017) doi:10.1038/nphys4181.
 T. Ozaki et al., Open source package for Material eXplorer, http://www.openmx-square.org/
 A. A. Mostofi et al., http://www.wannier.org.
 Y. P. Mizuta and F. Ishii, Scientific Reports 6, 28076 (2016).