Large thermoelectric response of metallic perovskites: ${\mathrm{Sr}}_{1-x}{\mathrm{La}}_x{\mathrm{TiO}}_3\hspace{0.5em}(0\mathrm{}<~x<~0.1)$

Thermoelectric properties have been investigated for single crystals of ${\mathrm{Sr}}_{1-x}{\mathrm{La}}_x{\mathrm{TiO}}_3$ for $0<~x<~\mathrm{0.1.}$ We have found a large power factor (defined as $\mathrm{PF}{=S}^2/\rho ,$ S and $\rho$ being the Seebeck coefficient and resistivity, respectively), $28-36\hspace{0.5em}\mu \mathrm{W}/\left({\mathrm{K}}^2\hspace{0.5em}\mathrm{cm}\right),$ at room temperature in the metallic region with carrier density (n) of $\left(0.2\mathrm{}-2\right)\times {10}^{21}\hspace{0.5em}{\mathrm{cm}}^{-3}.$ The observed PF is comparable to that of ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ with much lower $n\hspace{0.5em}(\sim 1\times {10}^{19}\hspace{0.5em}{\mathrm{cm}}^{-3}).\mathrm{}$ Such an unexpectedly large PF or S at the metallic carrier density is ascribed to the orbital degeneracy (threefold) of the Ti $3d-t_{2g}$ conduction band and the relatively large effective mass of conduction electrons as well as to the large energy-dependent scattering rate.