Cesium-involved electron transfer and electron-electron interaction in high-pressure metallic CsPbI3

TL;DR

This study reveals that electron-electron interactions, influenced by cesium-involved electron transfer, significantly affect the low-temperature electrical transport and induce Fermi liquid behavior in high-pressure CsPbI3, challenging the traditional electron-phonon coupling paradigm.

Contribution

It demonstrates the prominent role of electron-electron interactions in compressed CsPbI3 and links this to cesium-involved electron transfer and high-pressure phase transitions.

Findings

Insulator-to-metal transition at 80 GPa

Deviation from Fermi liquid behavior in the epsilon phase

Enhanced electron-electron coupling related to Cs-involved electron transfer

Abstract

Electron-phonon coupling was believed to govern the carrier transport in halide perovskites and related phases. Here we demonstrate that electron-electron interaction plays a direct and prominent role in the low-temperature electrical transport of compressed CsPbI3 and renders Fermi liquid (FL)-like behavior. By compressing {\delta}-CsPbI3 to 80 GPa, an insulator-to-metal transition occurs, concomitant with the completion of a sluggish structural transition from the one-dimensional (1D) Pnma ({\delta}) phase to a 3D Pmn21 ({\epsilon}) phase. Deviation from FL behavior is observed in CsPbI3 upon entering the metallic {\epsilon} phase, which progressively evolves into a FL-like state at 186 GPa. First-principles density functional theory calculations reveal that the enhanced electron-electron coupling is related to the Cs-involved electron transfer and sudden increase of the 5d state occupation of the high-pressure {\epsilon} phase. Our study presents a promising strategy for tuning the electronic interaction in halide perovskites for realizing intriguing electronic states.