Transport and thermoelectric properties of the ${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$ interface

The transport and thermoelectric properties of the interface between ${\mathrm{SrTiO}}_3$ and a 26-monolayer-thick ${\mathrm{LaAlO}}_3$ layer grown at high oxygen pressure have been investigated at temperatures from 4.2 to 100 K and in magnetic fields up to 18 T. For $T>4.2\mathrm{K}$, two different electronlike charge carriers originating from two electron channels which contribute to transport are observed. We probe the contributions of a degenerate and a nondegenerate band to the thermoelectric power and develop a consistent model to describe the temperature dependence of the thermoelectric tensor. Anomalies in the data point to an additional magnetic field dependent scattering.

Figure 1

(a) Temperature dependence of sheet resistance (line). Sheet resistance from the two-charge-carrier model (dots). (b) Sheet resistance (black line) and Hall resistance (dashed red line) at 4 K showing the negative magnetoresistance and the linear Hall effect. (c) Measured sheet resistance $R_{xx}$ for temperature between 4 and 100 K. (d) Measured Hall resistivity for temperature between 4 and 100 K (empty dots). Fits with the two-charge-carrier model (lines).

Figure 2

(a) Charge-carrier densities of the two electronlike bands $n_1$, $n_2$ from the two-charge-carrier model (inset: Arrhenuis plot for $n_2$). (b) Mobilities of the two electronlike bands ${\mu }_1$, ${\mu }_2$ from the two-charge-carrier model.

Figure 3

(a) Zero-field thermoelectric power $S_{xx}$ in a semilogarithmic plot for clarity. A small deviation from the observed $T^{0.4}$ dependence around 15 K is marked by an asterisk. (b) Magnetothermopower MS (see text) for selected temperatures. (c) Nernst effect $S_{xy}$ for selected temperatures.

Figure 4

(a) Temperature dependence of ${\epsilon }_{xx}$ (black dots). For illustration typical curves for degenerate and nondegenerate electrons are shown (see text). (b) Magnetic field dependence of ${\epsilon }_{xx}$ for selected temperatures between 4 and 100 K. (c) Magnetic field dependence of ${\epsilon }_{xy}$ for selected temperatures between 4 and 100 K.