Sr$_2$(Ba$_2$)VO$_4$ under pressure -- an orbital switch and potential $d^1$ superconductor

TL;DR

This study investigates how uniaxial pressure induces an orbital switch in Sr$_2$(Ba$_2$)VO$_4$, potentially transforming it into a $d^1$ superconductor similar to cuprates, with significant changes in its physical properties.

Contribution

The paper demonstrates that uniaxial pressure causes an orbital polarization in Sr$_2$(Ba$_2$)VO$_4$, leading to a possible $d^1$ superconducting state, a novel insight into pressure-induced electronic phase transitions.

Findings

Orbital polarization occurs under uniaxial pressure.

Pressure induces a $d^1$ state analogous to cuprates.

Significant changes in magnetic, optical, and transport properties.

Abstract

We study Sr$_2$(Ba$_2$)VO$_4$ under high pressure by means of the local density approximation + dynamical mean field theory method. While Sr$_2$VO$_4$ is a 1/6-filling three-band system at ambient pressure with a small level splitting between the $d_{xy}$- and $d_{yz/zx}$-bands, we show that an orbital polarization occurs under uniaxial pressure, resulting in dramatic changes of the magnetic, optical, and transport properties. When pressure is applied in the $c$-direction, a $d^1$ analog of $d^9$ cuprates is realized, making Sr$_2$(Ba$_2$)VO$_4$ a possible candidate for a $d^1$ superconductor. Experimentally, this uniaxial pressure can be realized by growing Ba$_2$VO$_4$ on a substrate with lattice constant 4.1-4.2 \AA.