Photo-excitation band-structure engineering of 2H-NbSe\(_2\) probed by time- and angle-resolved photoemission spectroscopy

• Published in: arXiv.org
• Main Authors: Watanabe, Mari, Suzuki, Takeshi, Someya, Takashi, Ogawa, Yu, Michimae, Shoya, Fujisawa, Masami, Kanai, Teruto, Itatani, Jiro, Saitoh, Tomohiko, Shin, Shik, Okazaki, Kozo
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 08.10.2020
• Subjects: Band structure of solids; Electron states; Electronic structure; Energy gap; Excitation; Fermi surfaces; Photoelectric emission; Photoelectron spectroscopy; Photoelectrons; Spectrum analysis
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2010.03751

We investigated the nonequilibrium electronic structure of 2H-NbSe\(_2\) by time- and angle-resolved photoemission spectroscopy. We find that the band structure is distinctively modulated by strong photo-excitation, as indicated by the unusual increase in the photoelectron intensities around E\(_F\). In order to gain insight into the observed photo-induced electronic state, we performed DFT calculations with modulated lattice structures, and found that the variation of the Se height from the Nb layer results in a significant change in the effective mass and band gap energy. We further study the momentum-dependent carrier dynamics. The results suggest that the relaxation is faster at the K-centered Fermi surface than at the \(\Gamma\)-centered Fermi surface, which can be attributed to the stronger electron-lattice coupling at the K-centered Fermi surface. Our demonstration of band structure engineering suggests a new role for light as a tool for controlling the functionalities of solid-state materials.