Bandwidth-driven nature of the pressure-induced metal state of LaMnO3

TL;DR

This study reveals that in LaMnO3, the insulator-to-metal transition under pressure is driven by band overlap rather than Jahn-Teller distortion reduction, with phase coexistence and hysteresis observed over a broad pressure range.

Contribution

It demonstrates that the pressure-induced IM transition in LaMnO3 occurs without significant Jahn-Teller distortion reduction, highlighting band overlap as the key mechanism.

Findings

Hysteretic phase coexistence between 7 and 25 GPa.

Electronic delocalization indicated by XAS pre-edge structure at 30 GPa.

IM transition occurs without reduction in Jahn-Teller distortion.

Abstract

Using X-ray absorption spectroscopy (XAS), we studied the local structure in LaMnO3 under applied pressure across and well above the insulator to metal (IM) transition. A hysteretic behavior points to the coexistence of two phases within a large pressure range (7 to 25 GPa). The ambient phase with highly Jahn-Teller (JT) distorted MnO6 octahedra is progressively substituted by a new phase with less-distorted JT MnO6 units. The electronic delocalization leading to the IM transition is finger-printed from the pre-edge XAS structure around 30 GPa. We observed that the phase transition takes place without any significant reduction of the JT distortion. This entails band-overlap as the driving mechanism of the IM transition.