Enhanced effective mass in doped SrTiO3 and related perovskites

TL;DR

This study uses ab-initio calculations to analyze how doping and crystal deformation affect the effective mass in SrTiO3 and related perovskites, revealing electronic effects as the main factor for effective mass increase.

Contribution

It provides a detailed ab-initio analysis of how doping and structural deformation influence the effective mass in SrTiO3, clarifying the dominant electronic effects involved.

Findings

Nb-doping increases effective mass mainly due to e2g-band flattening.

Deformation significantly affects bandgap and effective DOS, aligning with experimental data.

Different dopants like La, Ba, and V alter the effective mass in predictable ways.

Abstract

The effective mass is one of the main factors determining the Seebeck coefficient and electronic conductivity. Nb-doping increases the effective mass because of two reasons, lattice constants increase and electronic effects. In this ab-initio study the effective mass is estimated from the curvature of electronic bands and it could be clarified that the deformation of SrTiO3 crystals has a significant influence on bandgap and effective DOS and band mass, which are both in excellent agreement to experimental data. However, the electronic effect due to the e2g- band flattening near the Gamma-point due to Nb-doping up to 0.2 at% is the main factor for the increase of effective mass. Doping of La shows a linear decrease of the effective mass; this is explained by the different surrounding of A- and B-site. Substitution of other elements like Ba on the A-site and V on the B-site in SrTiO3 were also found to increase the effective mass.