Anomalous electronic and thermoelectric transport properties in cubic Rb3AuO antiperovskite

We use first-principles calculations combined with self-consistent phonon (SCP) theory, electron-phonon (e-ph) coupling, and the Boltzmann transport equation (BTE) to investigate the electronic and thermoelectric transport properties in the cubic Rb3AuO antiperovskite with strongly cubic and quartic lattice anharmonicity. The combination of SCP theory and Wannier-Fourier interpolation is used to calculate the e-ph coupling due to the failure of density functional perturbation theory in solving e-ph matrix elements for a strongly anharmonic crystal. Our results exhibit that a high electron mobility mu(e), e.g., similar to 454 cm(2)/Vs at 300 K from the iterative BTE solution, and a relatively weak temperature dependence of mu(e) proportional to T-11 are obtained in the n-type cubic Rb3AuO. We demonstrate that the coupling between electrons and polar optical phonons is responsible for the good charge transport, which, along with the high thermopower deriving from a light and threefold degenerate conduction-band pocket around the X point, leads to a very high power factor reaching 5.5 mW/mK(2) at 800 K. Meanwhile, a low lattice thermal conductivity and an undersized Lorenz number that signifies a resulting low electron thermal conductivity are also detected. As a result, a good thermoelectric performance with a figure of merit ZT similar to 1.02 at 300 K and an anomalously high ZT similar to 3.02 at 800 K is captured in the n-type cubic Rb3AuO. This finding breaks the long-term record of ZT < 3 in most of the reported bulk thermoelectric materials to date, and illustrates that the cubic Rb3AuO is an excellent candidate for thermoelectric applications.