Thermopower of the electron-doped manganese pnictide LaMnAsO

Abstract

Upon chemical substitution of oxygen with fluor, LaMnAsO has been electron-doped in experiments, resulting in samples with remarkably high Seebeck coefficients of around −300 µV K −1 at room temperature and 3% doping. Within the framework of density functional theory plus dynamical mean-field theory we are not only able to reproduce these experimental observations, but can also provide a thorough investigation of the underlying mechanisms. By considering electronic correlations in the half-filled Mn-3d shells, we trace the high Seebeck coefficient back to an asymmetry in the spectral function, which is due to emergence of incoherent spectral weight under doping and a strong renormalisation of the unoccupied states. This is only possible in correlated systems and cannot be explained by DFT-based band structure calculations.

Potential energy contribution to the thermopower of correlated electrons

“…As mentioned earlier, the Seebeck coefficient is sensitive to the particle-hole asymmetry around the chemical potential in the spectral functions (or density of states), in the current matrix elements (velocity matrices) and in the energy-dependent scattering rates. 11,[22][23][24][25] These quantities are not independent of each other. Consider our model in the absence of interaction.…”