Ultrafast carrier and phonon dynamics in Bi2Se3 crystals

TL;DR

This study investigates ultrafast carrier and phonon dynamics in Bi2Se3 crystals using pump-probe spectroscopy, revealing multiple relaxation processes influenced by electron-phonon interactions, defects, and environmental exposure.

Contribution

It provides new insights into the relaxation mechanisms and environmental effects on ultrafast dynamics in Bi2Se3, a topological insulator.

Findings

Three distinct relaxation processes identified.

Electron-phonon interactions and defect trapping are key mechanisms.

Environmental exposure alters relaxation dynamics and photon energy dependence.

Abstract

Ultrafast time-resolved differential reflectivity of Bi2Se3 crystals is studied using optical pump-probe spectroscopy. Three distinct relaxation processes are found to contribute to the initial transient reflectivity changes. The deduced relaxation timescale and the sign of the reflectivity change suggest that electron-phonon interactions and defect-induced charge trapping are the underlying mechanisms for the three processes. After the crystal is exposed to air, the relative strength of these processes is altered and becomes strongly dependent on the excitation photon energy.