Structure and Correlation Effects in Semiconducting SrTiO$_{3}$

TL;DR

This study uses angle-resolved photoemission spectroscopy to explore how structural phase transitions and electron correlations affect the electronic properties of SrTiO$_{3}$, revealing charge transfer, correlation effects, and polaron formation.

Contribution

It provides experimental insights into the effects of structural phase transition and electron correlation on SrTiO$_{3}$'s electronic structure, challenging theoretical predictions.

Findings

Charge transfer from in-plane to out-of-plane bands at 105K transition.

Smooth evolution of quasiparticle strength and effective masses.

Evidence of polaron formation indicated by peak-dip-hump lineshape.

Abstract

We have investigated the effects of structure change and electron correlation on SrTiO$_{3}$ single crystals using angle-resolved photoemission spectroscopy. We show that the cubic to tetragonal phase transition at 105$^\circ$K is manifested by a charge transfer from in-plane ($d_{yz}$ and $d_{zx}$) bands to out-of-plane ($d_{xy}$) band, which is opposite to the theoretical predictions. Along this second-order phase transition, we find a smooth evolution of the quasiparticle strength and effective masses. The in-plane band exhibits a peak-dip-hump lineshape, indicating a high degree of correlation on a relatively large (170 meV) energy scale, which is attributed to the polaron formation.