Observation of highly anisotropic bulk dispersion and spin-polarized topological surface states in CoTe2

We present CoTe2 as a type-II Dirac semimetal supporting Lorentz-symmetry violating Dirac fermions in the vicinity of the Fermi energy. By combining first-principles ab initio calculations with experimental angle-resolved photoemission spectroscopy results, we show CoTe2 hosts a pair of type-II Dirac fermions around 90 meV above the Fermi energy. In addition to the bulk Dirac fermions, we find several topological band inversions in bulk CoTe2, which gives rise to a ladder of spin-polarized surface states over a wide range of energies. In contrast to the surface states which typically display Rashba-type in-plane spin splitting, we find that CoTe2 hosts interesting out-of-plane spin polarization as well. Our work establishes CoTe2 as a potential candidate for the exploration of Dirac fermiology and applications in spintronic devices, infrared plasmonics, and ultrafast optoelectronics.

Automated summary

We present CoTe2 as a type-II Dirac semimetal hosting Lorentz-symmetry violating Dirac fermions near the Fermi energy. Combining ab initio calculations and experimental results, we find a pair of type-II Dirac fermions in CoTe2 above the Fermi energy. In addition, CoTe2 exhibits several topological band inversions and spin-polarized surface states, including out-of-plane spin polarization. This work establishes CoTe2 as a potential candidate for studying Dirac fermiology and applications in spintronic devices, infrared plasmonics, and ultrafast optoelectronics.