Magnetic Weyl semimetals (WSMs) bearing long-time pursuing are still very rare. We herein identified magnetic exchange induced Weyl state in EuCd2Sb2, a semimetal in type IV magnetic space group, via performing high magnetic field (B) magneto-transport measurements and ab initio calculations. For the A-type antiferromagnetic (AFM) structure of EuCd2Sb2, external B larger than 3.2 T can align Eu spins to be fully polarized along the c-axis and consequently drive the system into a ferromagnetic (FM) state. Measurements up to B ~ 55 T revealed a striking Shubnikov-de Hass oscillation imposed by a nontrivial Berry phase. We unveiled a phase transition from a small-gap AFM topological insulator into a FM WSM in which Weyl points emerged along the {\Gamma}-Z path. Fermi arcs on (100) and (010) surfaces are also revealed. The results pave a way towards realization of various topological states in a single material through magnetic exchange manipulation.
@article{arxiv.1903.12532,
title = {Magnetic exchange induced Weyl state in a semimetal EuCd2Sb2},
author = {Hao Su and Benchao Gong and Wujun Shi and Haifeng Yang and Hongyuan Wang and Wei Xia and Zhenhai Yu and Peng-Jie Guo and Jinhua Wang and Linchao Ding and Liangcai Xu and Xiaokang Li and Xia Wang and Zhiqiang Zou and Na Yu and Zengwei Zhu and Yulin Chen and Zhongkai Liu and Kai Liu and Gang Li and Yanfeng Guo},
journal= {arXiv preprint arXiv:1903.12532},
year = {2019}
}