Origin of large thermopower in LiRh${}_2$O${}_4$

Abstract

Motivated by the newly synthesized mixed-valent spinel LiRh${}_2$O${}_4$ for which a large thermopower is observed in the metallic cubic phase above 230K [Okamoto {\it et al.} (arXiv:0806.2504)], we calculate the Seebeck coefficient by the combination of local density approximation and dynamical mean field theory (LDA+DMFT). The experimental values are well reproduced not only by LDA+DMFT but also by the less involved Boltzmann equation approach. A careful analysis of the latter shows unexpectedly that the origin of the large thermopower shares a common root with a very different oxide: Na${}_x$CoO${}_2$. We also discuss how it is possible to further increase the powerfactor of LiRh${}_2$O${}_4$ through doping, which makes the material even more promoising for technological applications.

5 pages, 5 figures