Magnetothermopower of $\delta$-doped LaTiO$_3$/SrTiO$_3$ interfaces in the Kondo regime

TL;DR

This study investigates the magnetothermopower of delta-doped LaTiO3/SrTiO3 interfaces, revealing Kondo scattering effects and magnetic field suppression, advancing understanding of thermoelectric behavior in complex oxide interfaces.

Contribution

It demonstrates the enhancement of thermopower due to delta doping and confirms Kondo scattering as the mechanism affecting thermopower at low temperatures.

Findings

Thermopower increases with delta doping.

S(T) shows a maximum below 100 K linked to Kondo effect.

Magnetic field suppresses thermopower isotropically.

Abstract

Measurements of magneto-thermopower (S(H, T)) of interfacial delta doped LaTiO$_3$/SrTiO$_3$ (LTO/STO) heterostructure by an iso-structural antiferromagnetic perovskite LaCrO$_3$ are reported. The thermoelectric power of the pure LTO/STO interface at 300 K is $\approx$ 118 $\mu$V/K, but increases dramatically on $\delta$-doping. The observed linear temperature dependence of S(T) over the temperature range 100 K to 300 K is in agreement with the theory of diffusion thermopower of a two-dimensional electron gas. The S(T) displays a distinct enhancement in the temperature range (T $<$ 100 K) where the sheet resistance shows a Kondo-type minimum. We attributed this maximum in S(T) to Kondo scattering of conduction electron by localized impurity spins at the interface. The suppression of S by a magnetic field, and the isotropic nature of the suppression in out-of-plane and in-plane field geometries further strengthen the Kondo model based interpretation of S(H, T).