Abstract
Transition-metal dichalcogenides (TMDs) offer an ideal platform to experimentally realize Dirac fermions. However, typically these exotic quasiparticles are located far away from the Fermi level, limiting the contribution of Dirac-like carriers to the transport properties. Here we show that NiTe2 hosts both bulk Type-II Dirac points and topological surface states. The underlying mechanism is shared with other TMDs and based on the generic topological character of the Te p-orbital manifold. However, unique to NiTe2, a significant contribution of Ni d orbital states shifts the energy of the Type-II Dirac point close to the Fermi level. In addition, one of the topological surface states intersects the Fermi energy and exhibits a remarkably large spin splitting of 120 meV. Our results establish NiTe2 as an exciting candidate for next-generation spintronics devices.
Highlights
Transition-metal dichalcogenides (TMDs) offer an ideal platform to experimentally realize Dirac fermions
We demonstrate with a combination of angular resolved photoemission spectroscopy (ARPES) and comprehensive Density functional theory (DFT) calculations that the band structure of N iTe2 shows the formation of type-II Dirac fermions near the Fermi level and a set of spin polarised topological surface states
Our tight-binding model incorporates two chalcogen sites (Fig. 1a), and captures the manner in which the chalcogenide p orbital manifold develops into dispersive bands which generically possess topological characteristics: bulk Dirac points, inverted band gaps (IBGs), and topologically protected surface states (TSS)
Summary
Transition-metal dichalcogenides (TMDs) offer an ideal platform to experimentally realize Dirac fermions Typically these exotic quasiparticles are located far away from the Fermi level, limiting the contribution of Dirac-like carriers to the transport properties. Density functional theory (DFT) calculations for a wide range of compounds predict a set of bulk Dirac points and band inversions (associated with topological surface states, TSS), as the chalcogen orbital symmetries combined with a natural hierarchy of energy scales ensure that these states exist rather generically. We demonstrate with a combination of ARPES and comprehensive DFT calculations that the band structure of N iTe2 shows the formation of type-II Dirac fermions near the Fermi level and a set of spin polarised topological surface states. The measured Fermi surface map matches well with our calculations and the observation of electron pockets implies finite contribution of
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