Friday, June 7, 2013

1306.1494 (A. Rastogi et al.)

Coulomb correlations and enhanced thermopower in δ-doped
LaAlO3-SrTiO3 interface

A. Rastogi, J. J. Pulikkotil, Z. Hossain, D. Kumar, R. C. Budhani
In the paradigm of one electron band theory, the size quantization effects are expected to increase thermopower in carrier confined systems. However, this is not observed in case of the SrTiO3 quantum wells, probably due to the finite extent of the interfacial electron gas in the third dimension. Here, we investigate LaAlO3-SrTiO3 heterostructure interface with \delta-doping of a LaMnO3 sub-monolayer. This results in a giant increase in thermopower. The resistivity measurements give evidence for strong Coulomb correlations in the \delta-doped heterostructures. We present model calculations based on modified Heikes formula which attribute the thermopower enhancement to the increased spin and orbital entropy originating from the LaMnO3 sub-monolayer. Furthermore, a weak effect of magnetic field on thermopower can also be qualitatively understood in the model.
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