# Ultraquantum magnetoresistance in the Kramers-Weyl semimetal candidate $\beta− Ag_2 Se$

Zhang, Cheng-Long; Schindler, Frank; Liu, Haiwen; Chang, Tay-Rong; Xu, Su-Yang; Chang, Guoqing; Hua, Wei; Jiang, Hua; Yuan, Zhujun; Sun, Junliang; Jeng, Horng-Tay; Lu, Hai-Zhou; Lin, Hsin; Hasan, M Zahid; Xie, X C; Neupert, Titus; Jia, Shuang (2017). Ultraquantum magnetoresistance in the Kramers-Weyl semimetal candidate $\beta− Ag_2 Se$. Physical review. B, 96:165148.

## Abstract

The topological semimetal $\beta− Ag_2 Se$ features a Kramers-Weyl node at the origin in momentum space and a quadruplet of spinless Weyl nodes, which are annihilated by spin-orbit coupling. We show that single-crystalline $\beta− Ag_2 Se$ manifests giant Shubnikov–de Haas oscillations in the longitudinal magnetoresistance, which stem from a small electron pocket that can be driven beyond the quantum limit by a field less than 9 T. This small electron pocket is a remainder of the spin-orbit annihilated Weyl nodes and thus encloses a Berry-phase structure. Moreover, we observed a negative longitudinal magnetoresistance when the magnetic field is beyond the quantum limit. Our experimental findings are complemented by thorough theoretical band-structure analyses of this Kramers-Weyl semimetal candidate, including first-principles calculations and an effective $k \centerdot p$ model.

## Abstract

The topological semimetal $\beta− Ag_2 Se$ features a Kramers-Weyl node at the origin in momentum space and a quadruplet of spinless Weyl nodes, which are annihilated by spin-orbit coupling. We show that single-crystalline $\beta− Ag_2 Se$ manifests giant Shubnikov–de Haas oscillations in the longitudinal magnetoresistance, which stem from a small electron pocket that can be driven beyond the quantum limit by a field less than 9 T. This small electron pocket is a remainder of the spin-orbit annihilated Weyl nodes and thus encloses a Berry-phase structure. Moreover, we observed a negative longitudinal magnetoresistance when the magnetic field is beyond the quantum limit. Our experimental findings are complemented by thorough theoretical band-structure analyses of this Kramers-Weyl semimetal candidate, including first-principles calculations and an effective $k \centerdot p$ model.

## Statistics

### Citations

Dimensions.ai Metrics