Response of the lattice across the filling-controlled Mott metal-insulator transition of a rare earth titanate

TL;DR

This study investigates how the lattice structure of SmTiO3 changes with hole doping across the Mott metal-insulator transition, revealing gradual distortion reduction without phase separation and persistent distortions in the metallic state.

Contribution

It provides atomic-scale insights into lattice distortions during the filling-controlled Mott transition, using high-resolution microscopy to observe gradual and uniform lattice changes.

Findings

Lattice distortions decrease gradually with doping

No phase separation observed during transition

Distortions persist into the metallic state

Abstract

The lattice response of a prototype Mott insulator, SmTiO3, to hole doping is investigated with atomic-scale spatial resolution. SmTiO3 films are doped with Sr on the Sm site with concentrations that span the insulating and metallic sides of the filling-controlled Mott metal-insulator transition (MIT). The GdFeO3-type distortions are investigated using an atomic resolution scanning transmission electron microscopy technique that can resolve small lattice distortions with picometer precision. We show that these distortions are gradually and uniformly reduced as the Sr concentration is increased without any phase separation. Significant distortions persist into the metallic state. The results present a new picture of the physics of this prototype filling-controlled MIT, which is discussed.