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Thermopower enhancement by fractional layer control in 2D oxide superlattices

We have investigated two-dimensional thermoelectric properties in transition metal oxide heterostructures. In particular, we adopted an unprecedented approach to direct tuning of the 2D carrier density using fractionally δ-doped oxide superlattices. By artificially controlling the carrier density in the 2D electron gas that emerges at a LaxSr1-xTiO3 δ-doped layer, we demonstrate that a thermopower as large as 408 μV K-1 can be reached. This approach also yielded a power factor of the 2D carriers 117 μWcm-1K-2, which is one of the largest reported values from transition metal oxide based materials. The promising result can be attributed to the anisotropic band structure in the 2D system, indicating that δ-doped oxide superlattices can be a good candidate for advanced thermoelectrics.