3 years ago

# Theoretical prediction of magnetic and noncentrosymmetric Weyl fermion semimetal states in the R-Al-X family of compounds (R=rare earth, Al=aluminium, X=Si, Ge).

Daniel S. Sanchez, Yi Bian, Xiao Zhang, Hsin Lin, Nasser Alidoust, Guang Bian, Arun Bansil, Shuang Jia, Guoqing Chang, Han Hsu, Tay-Rong Chang, Ilya Belopolski, Shin-Ming Huang, Su-Yang Xu, Hao Zheng, M. Zahid Hasan, Titus Neupert, Hong Lu, Horng-Tay Jeng, Chuang-Han Hsu, Bahadur Singh

Weyl semimetals are novel topological conductors that host Weyl fermions as emergent quasiparticles. While the Weyl fermions in high-energy physics are strictly defined as the massless solution of the Dirac equation and uniquely fixed by Lorentz symmetry, there is no such constraint for a topological metal in general. Specifically, the Weyl quasiparticles can arise by breaking either the space-inversion ($\mathcal{I}$) or time-reversal ($\mathcal{T}$) symmetry. They can either respect Lorentz symmetry (type-I) or strongly violate it (type-II). To date, different types of Weyl fermions have been predicted to occur only in different classes of materials. In this paper, we present a significant materials breakthrough by identifying a large class of Weyl materials in the RAlX (R=Rare earth, Al, X=Ge, Si) family that can realize all different types of emergent Weyl fermions ($\mathcal{I}$-breaking, $\mathcal{T}$-breaking, type-I or type-II), depending on a suitable choice of the rare earth elements. Specifically, RAlX can be ferromagnetic, nonmagnetic or antiferromagnetic and the electronic band topology and topological nature of the Weyl fermions can be tuned. The unparalleled tunability and the large number of compounds make the RAlX family of compounds a unique Weyl semimetal class for exploring the wide-ranging topological phenomena associated with different types of emergent Weyl fermions in transport, spectroscopic and device-based experiments.

Publisher URL: http://arxiv.org/abs/1604.02124

DOI: arXiv:1604.02124v4

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