# Low-energy type-II Dirac fermions and spin-polarized topological surface states in transition-metal dichalcogenide NiTe$_2$

## TL;DR

This study identifies low-energy type-II Dirac fermions and spin-polarized topological surface states in NiTe₂, revealing its potential for spintronics and ultrafast optoelectronic applications through combined experimental and theoretical analysis.

## Contribution

The paper demonstrates the existence of a low-energy type-II Dirac semimetal state in NiTe₂ and characterizes its topological surface states with chiral spin texture, using spin-ARPES and ab initio calculations.

## Key findings

- Dirac node near Fermi energy in NiTe₂
- Topological surface states with chiral spin texture
- Band inversions supporting Dirac cone surface states

## Abstract

Using spin- and angle- resolved photoemission spectroscopy (spin-ARPES) together with ${\it ab~initio}$ calculations, we demonstrate the existence of a type-II Dirac semimetal state in NiTe$_2$. We show that, unlike PtTe$_2$, PtSe$_2$, and PdTe$_2$, the Dirac node in NiTe$_2$ is located in close vicinity of the Fermi energy. Additionally, NiTe$_2$ also hosts a pair of band inversions below the Fermi level along the $\Gamma-A$ high-symmetry direction, with one of them leading to a Dirac cone in the surface states. The bulk Dirac nodes and the ladder of band inversions in NiTe$_2$ support unique topological surface states with chiral spin texture over a wide range of energies. Our work paves the way for the exploitation of the low-energy type-II Dirac fermions in NiTe$_2$ in the fields of spintronics, THz plasmonics and ultrafast optoelectronics.