Lorentz-violating type-II Dirac fermions in transition metal dichalcogenide PtTe2

Mingzhe Yan,Zhe Sun,Wenhui Duan,Hong Yao,Yang Wu,Shuyun Zhou,Huaqing Huang,Eryin Wang,Hongyun Zhang,Shoushan Fan,Haitao Yang,Kenan Zhang,Ke Deng,Masashi Arita,Guoliang Wan,Wei Yao

doi:10.1038/s41467-017-00280-6

Abstract

Topological semimetals have recently attracted extensive research interests as host materials to condensed matter physics counterparts of Dirac and Weyl fermions originally proposed in high energy physics. Although Lorentz invariance is required in high energy physics, it is not necessarily obeyed in condensed matter physics, and thus Lorentz-violating type-II Weyl/Dirac fermions could be realized in topological semimetals. The recent realization of type-II Weyl fermions raises the question whether their spin-degenerate counterpart—type-II Dirac fermions—can be experimentally realized too. Here, we report the experimental evidence of type-II Dirac fermions in bulk stoichiometric PtTe2 single crystal. Angle-resolved photoemission spectroscopy measurements and first-principles calculations reveal a pair of strongly tilted Dirac cones along the Γ-A direction, confirming PtTe2 as a type-II Dirac semimetal. Our results provide opportunities for investigating novel quantum phenomena (e.g., anisotropic magneto-transport) and topological phase transition.

Highlights

Topological semimetals have recently attracted extensive research interests as host materials to condensed matter physics counterparts of Dirac and Weyl fermions originally proposed in high energy physics
By combining angle-resolved photoemission spectroscopy (ARPES) measurements and firstprinciples calculations, we report the experimental evidence of type-II Dirac fermions in bulk PtTe2 single crystal with a pair of strongly tilted Dirac cones
To reveal the bulk versus surface properties of these Dirac cones, we show in Fig. 3 ARPES data measured along the Γ-K and Γ-M directions using different photon energies

Summary

Introduction

Topological semimetals have recently attracted extensive research interests as host materials to condensed matter physics counterparts of Dirac and Weyl fermions originally proposed in high energy physics. When T(k) > U(k) along certain momentum direction, the Lorentz invariance is violated and strongly titled Dirac cones emerge at the topologically protected touching points between electron and hole pockets (Fig. 1b). By combining angle-resolved photoemission spectroscopy (ARPES) measurements and firstprinciples calculations, we report the experimental evidence of type-II Dirac fermions in bulk PtTe2 single crystal with a pair of strongly tilted Dirac cones.

Results

Conclusion