Doping-induced dimensional crossover and thermopower burst in Nb-doped SrTiO${}_3$ superlattices

Abstract

Using advanced ab-initio calculations, we describe the formation and confinement of a two-dimensional electron gas in short-period ($\simeq$4 nm) Nb-doped SrTiO${}_3$ superlattices as function of Nb doping. We predict complete two-dimensional confinement for doping concentrations higher than 70%. In agreement with previous observations, we find a large thermopower enhancement at room temperature. However, this effect is primarily determined by dilution of the mobile charge over a multitude of weakly occupied bands. As a general rule, we conclude that thermopower in similar heterostructures will be more enhanced by weak, rathern than tight spatial confinement.

8 pages, 8 figures

References in corpus (3)

• BoltzTraP. A code for calculating band-structure dependent quantities
• Ordering and multiple phase transitions in ultra-thin nickelate superlattices
• Origin of coexisting large Seebeck coefficient and metallic conductivity in the electron doped SrTiO${}_3$ and KTaO${}_3$

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