Carrier and Phonon Dynamics in Multilayer WSe2 captured by Extreme Ultraviolet Transient Absorption Spectroscopy

TL;DR

This study uses extreme ultraviolet transient absorption spectroscopy to investigate carrier and phonon dynamics in multilayer WSe2, revealing ultrafast processes and element-specific signals crucial for electronic and photonic applications.

Contribution

It introduces a novel XUV transient absorption approach to simultaneously monitor holes and phonons in multilayer WSe2, advancing understanding of ultrafast dynamics in layered materials.

Findings

Hole relaxation time: 0.4 ps

Carrier recombination time: 1.5 ps

Phonon heating time: 1.7 ps

Abstract

Carrier and phonon dynamics in a multilayer WSe2 film are captured by extreme ultraviolet (XUV) transient absorption (TA) spectroscopy at the W N6,7, W O2,3, and Se M4,5 edges (30-60 eV). After the broadband optical pump pulse, the XUV probe directly reports on occupations of optically excited holes and phonon-induced band renormalizations. By comparing with density functional theory calculations, XUV transient absorption due to holes are identified below the W O3 edge whereas signals at the Se M4,5 edges are dominated by phonon dynamics. Therein, 0.4 ps hole relaxation time, 1.5 ps carrier recombination time, and 1.7 ps phonon heating time are extracted. The acquisition of hole and phonon-induced signals in a single experiment can facilitate the investigation of the correlations between electron and phonon dynamics. Furthermore, the simultaneous observation of signals from different elements can be further extended to explore photochemical processes in multilayers and alloys, thereby providing key information for their applications in electronics, photocatalysts, and spintronics.