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arXiv · 2010.03751

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

Mari Watanabe·Takeshi Suzuki·Takashi Someya·Yu Ogawa·Shoya Michimae·Masami Fujisawa·Teruto Kanai·Jiro Itatani·Tomohiko Saitoh·Shik Shin·Kozo Okazaki
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Abstract

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.

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Mari Watanabe, Takeshi Suzuki, Takashi Someya, Yu Ogawa, Shoya Michimae, Masami Fujisawa, Teruto Kanai, Jiro Itatani, Tomohiko Saitoh, Shik Shin, Kozo Okazaki. 2020-10-08. Photo-excitation band-structure engineering of 2H-NbSe$_2$ probed by time- and angle-resolved photoemission spectroscopy. https://doi.org/10.7566/jpsj.91.064703

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