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arXiv · 2108.10874

Kramers-Weyl fermions in the chiral charge density wave material (TaSe$_4$)$_2$I

Soyeun Kim·Robert C. McKay·Nina Bielinski·Chengxi Zhao·Meng-Kai Lin·Joseph A. Hlevyack·Xuefei Guo·Sung-Kwan Mo·Peter Abbamonte·Tai-Chang Chiang·André Schleife·Daniel P. Shoemaker·Barry Bradlyn·Fahad Mahmood
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Abstract

The quasi-one-dimensional chiral charge density wave (CDW) material (TaSe$_4$)$_2$I has been recently predicted to host Kramers-Weyl (KW) fermions which should exist in the vicinity of high symmetry points in the Brillouin zone in chiral materials with strong spin-orbit coupling. However, direct spectroscopic evidence of KW fermions is limited. Here we use helicity-dependent laser-based angle resolved photoemission spectroscopy (ARPES) in conjunction with tight-binding and first-principles calculations to identify KW fermions in (TaSe$_4$)$_2$I. We find that topological and symmetry considerations place distinct constraints on the (pseudo-) spin texture and the observed spectra around a KW node. We further reveal an interplay between the spin texture around the chiral KW node and the onset of CDW order in (TaSe$_4$)$_2$I. Our findings highlight the unique topological nature of (TaSe$_4$)$_2$I and provide a pathway for identifying KW fermions in other chiral materials.

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Soyeun Kim, Robert C. McKay, Nina Bielinski, Chengxi Zhao, Meng-Kai Lin, Joseph A. Hlevyack, Xuefei Guo, Sung-Kwan Mo, Peter Abbamonte, Tai-Chang Chiang, André Schleife, Daniel P. Shoemaker, Barry Bradlyn, Fahad Mahmood. 2021-08-24. Kramers-Weyl fermions in the chiral charge density wave material (TaSe$_4$)$_2$I. https://arxiv.org/abs/2108.10874

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