Measuring Chern numbers above the Fermi level in the Type II Weyl semimetal Mo$_x$W$_{1-x}$Te$_2$
Autor: | Belopolski, Ilya, Xu, Su-Yang, Ishida, Yukiaki, Pan, Xingchen, Yu, Peng, Sanchez, Daniel S., Neupane, Madhab, Alidoust, Nasser, Chang, Guoqing, Chang, Tay-Rong, Wu, Yun, Bian, Guang, Zheng, Hao, Huang, Shin-Ming, Lee, Chi-Cheng, Mou, Daixiang, Huang, Lunan, Song, You, Wang, Baigeng, Wang, Guanghou, Yeh, Yao-Wen, Yao, Nan, Rault, Julien E., Fèvre, Patrick Le, Bertran, François, Jeng, Horng-Tay, Kondo, Takeshi, Kaminski, Adam, Lin, Hsin, Liu, Zheng, Song, Fengqi, Shin, Shik, Hasan, M. Zahid |
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Rok vydání: | 2016 |
Předmět: | |
Zdroj: | Phys. Rev. B 94, 085127 (2016) |
Druh dokumentu: | Working Paper |
DOI: | 10.1103/PhysRevB.94.085127 |
Popis: | It has recently been proposed that electronic band structures in crystals give rise to a previously overlooked type of Weyl fermion, which violates Lorentz invariance and, consequently, is forbidden in particle physics. It was further predicted that Mo$_x$W$_{1-x}$Te$_2$ may realize such a Type II Weyl fermion. One crucial challenge is that the Weyl points in Mo$_x$W$_{1-x}$Te$_2$ are predicted to lie above the Fermi level. Here, by studying a simple model for a Type II Weyl cone, we clarify the importance of accessing the unoccupied band structure to demonstrate that Mo$_x$W$_{1-x}$Te$_2$ is a Weyl semimetal. Then, we use pump-probe angle-resolved photoemission spectroscopy (pump-probe ARPES) to directly observe the unoccupied band structure of Mo$_x$W$_{1-x}$Te$_2$. For the first time, we directly access states $> 0.2$ eV above the Fermi level. By comparing our results with $\textit{ab initio}$ calculations, we conclude that we directly observe the surface state containing the topological Fermi arc. Our work opens the way to studying the unoccupied band structure as well as the time-domain relaxation dynamics of Mo$_x$W$_{1-x}$Te$_2$ and related transition metal dichalcogenides. Comment: Incorporates earlier results presented in arXiv:1512.09099, by the same authors |
Databáze: | arXiv |
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