Coupled valence carrier and core-exciton dynamics in WS2 probed by few-femtosecond extreme ultraviolet transient absorption spectroscopy
- Authors
- Chang, Hung-Tzu; Guggenmos, Alexander; Chen, Christopher T.; Oh, Juwon; Geneaux, Romain; Chuang, Yi-De; Schwartzberg, Adam M.; Aloni, Shaul; Neumark, Daniel M.; Leone, Stephen R.
- Issue Date
- 23-Aug-2021
- Publisher
- AMER PHYSICAL SOC
- Citation
- Physical Review B, v.104, no.6
- Journal Title
- Physical Review B
- Volume
- 104
- Number
- 6
- URI
- https://scholarworks.bwise.kr/sch/handle/2021.sw.sch/19827
- DOI
- 10.1103/PhysRevB.104.064309
- ISSN
- 2469-9950
2469-9969
- Abstract
- Few-femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy, performed with optical 500-1000-nm supercontinuum and broadband XUV pulses (30-50 eV), simultaneously probes dynamics of photoexcited carriers in WS2 at the W O-3 edge (37-45 eV) and carrier-induced modifications of core-exciton absorption at the W N-6,N-7 edge (32-37 eV). Access to continuous core-to-conduction-band absorption features and discrete core-exciton transitions in the same XUV spectral region in a semiconductor provides a means to investigate the effect of carrier excitation on core-exciton dynamics. The core-level transient absorption spectra, measured with either pulse arriving first to explore both core-level and valence carrier dynamics, reveal that coreexciton transitions are strongly influenced by the photoexcited carriers. A 1.2 +/- 0.3 ps hole-phonon relaxation time and a 3.1 +/- 0.4 ps carrier recombination time are extracted from the XUV transient absorption spectra from the core-to-conduction-band transitions at the W O-3 edge. Global fitting of the transient absorption signal at the W N-6,N-7 edge yields similar to 10 fs coherence lifetimes of core-exciton states and reveals that the photoexcited carriers, which alter the electronic screening and band filling, are the dominant contributor to the spectral modifications of core excitons and direct field-induced changes play a minor role. This work provides a first look at the modulations of core-exciton states by photoexcited carriers and advances our understanding of carrier dynamics in metal dichalcogenides.
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