# Experimental evidence of type-II Dirac fermions in PtSe2

## TL;DR

This paper provides experimental evidence for the existence of three-dimensional type-II Dirac fermions in high-quality PtSe2 crystals, highlighting its potential for exploring novel quantum phenomena in topological semimetals.

## Contribution

It presents direct experimental evidence of type-II Dirac fermions in PtSe2, a significant step in understanding topological semimetals with Lorentz invariance breaking.

## Key findings

- Evidence of 3D type-II Dirac fermions in PtSe2
- Comparison of electronic structures between PtSe2 and PtTe2
- Identification of PtSe2 as a platform for quantum phenomena exploration

## Abstract

Topological semimetals have attracted extensive research interests for realizing condensed matter physics counterparts of three-dimensional Dirac and Weyl fermions, which were originally introduced in high energy physics. Recently it has been proposed that type-II Dirac semimetal can host a new type of Dirac fermions which break Lorentz invariance and therefore does not have counterpart in high energy physics. Here we report the electronic structure of high quality PtSe$_2$ crystals to provide direct evidence for the existence of three-dimensional type-II Dirac fermions. A comparison of the crystal, vibrational and electronic structure to a sister compound PtTe$_2$ is also discussed. Our work provides an important platform for exploring the novel quantum phenomena in the PtSe$_2$ class of type-II Dirac semimetals.