Observation of decoupling of electrons from phonon bath close to a correlation driven metal-insulator transition

TL;DR

This study demonstrates that near a Mott transition, electrons become decoupled from the phonon bath, evidenced by anomalously large thermal noise due to nanoscale metallic regions within an insulating matrix.

Contribution

It provides experimental evidence of electron-phonon decoupling near a correlation-driven metal-insulator transition using noise measurements in NdNiO3 films.

Findings

Large deviation in thermal noise from Johnson-Nyquist value near transition

Presence of nanoscale metallic pockets within insulating phase

Decoupling of electrons from thermal bath observed close to Mott transition

Abstract

We observed that close to a Mott transition, over a small temperature range, the predominance of slow relaxations leads to decoupling of electrons from the thermal bath. This has been established by observation of large deviation of the thermal noise in the films of Mott system $NdNiO_{3}$ from the canonical Johnson-Nyquist value of $4k_{B}TR$ close to the transition. It is suggested that such a large noise arise from small isolated pockets of nanometric metallic phases (estimated size $\sim$ 15-20 nm) within the insulating phase with the charging energy as the control parameter.