Glass-like electronic and thermal transport in crystalline cubic germanium selenide

Thermoelectric properties of orthorhombic or rhombohedral GeSe have attracted great attention recently, with the rise of its structural analog SnSe. However, the p-type cubic GeSe with higher symmetry and higher valence band degeneracy, which might exhibit higher thermoelectric performance, has never been synthesized. Here we report on the successful synthesis of p-type crystalline cubic GeSe by alloying with Sb₂Te₃ and the spontaneously formed Ge-vacancies. An unexpected glass-like temperature independent lattice thermal conductivity is observed in crystalline cubic GeSe, which results from strong phonon scattering by vacancy-induced disorders. Combining the multiple scattering theory and chemical bond analysis, we further reveal the existence of Anderson localization induced by Ge-vacancies. The Anderson localization results in a nearly constant Seebeck coefficient with increasing the carrier concentration. These results provide a general insight towards understanding and improving the thermoelectric properties of thermoelectric materials with vacancies and atomic-scale disorders.