Ultrafast electronic and lattice dynamics in laser-excited crystalline bismuth

TL;DR

This study uses femtosecond spectroscopy to investigate ultrafast electronic and lattice dynamics in crystalline bismuth, revealing multiple relaxation processes and wavevector-dependent electron-phonon interactions.

Contribution

It provides new insights into the relaxation timescales and wavevector dependence of electron-phonon coupling in bismuth using variable wavelength pump-probe spectroscopy.

Findings

Detection of relaxation components at 1 ps, 7 ps, and ~1 ns.

Observation of wavevector dependence in electron-phonon coupling.

Variation in coherent phonon parameters with excitation conditions.

Abstract

Femtosecond spectroscopy is applied to study transient electronic and lattice processes in bismuth. Components with relaxation times of 1 ps, 7 ps and ~ 1 ns are detected in the photoinduced reflectivity response of the crystal. To facilitate the assignment of the observed relaxation to the decay of particular excited electronic states we use pump pulses with central wavelengths ranging from 400 nm to 2.3 mum. Additionally, we examine the variation of parameters of coherent A1g phonons upon the change of excitation and probing conditions. Data analysis reveals a significant wavevector dependence of electron-hole and electron- phonon coupling strength along \Gamma--T direction of the Brillouin zone.