Thermopower Enhancement from Engineering the Na_(0.7)CoO_2 Interacting Fermiology via Fe Doping

摘要

The sodium cobaltate system Na_xCoO_2 is a prominent representant of strongly correlatedmaterials with promising thermoelectric response. In a combined theoretical and experimental study we show that, by doping the Co site of the compound at x = 0.7 with iron, a further increase of the Seebeck coefficient is achieved. The Fe defects give rise to effective hole doping in the highthermopower region of larger sodium content x. Originally filled hole pockets in the angular-resolved spectral function of the material shift to low energy when introducing Fe, leading to amultisheet interacting Fermi surface. Because of the higher sensitivity of correlated materials to doping, introducing adequate substitutional defects is thus a promising route to manipulate their thermopower.