# Manipulation of type-I and type-II Dirac points in PdTe2 superconductor by external pressure

## TL;DR

This study uses first-principles calculations to explore how hydrostatic pressure affects Dirac points in PdTe2, revealing the transition from type-II to type-I Dirac cones and their coexistence with superconductivity.

## Contribution

It demonstrates the pressure-induced evolution of Dirac cones in PdTe2, including the emergence of type-I Dirac points and the coexistence of both types under specific pressures.

## Key findings

- Type-II Dirac points disappear at 6.1 GPa.
- Type-I Dirac points emerge at 4.7 GPa.
- Superconductivity slightly decreases with pressure.

## Abstract

A pair of type-II Dirac cones in PdTe$_2$ was recently predicted by theories and confirmed in experiments, making PdTe$_2$ the first material that processes both superconductivity and type-II Dirac fermions. In this work, we study the evolution of Dirac cones in PdTe$_2$ under hydrostatic pressure by the first-principles calculations. Our results show that the pair of type-II Dirac points disappears at 6.1 GPa. Interestingly, a new pair of type-I Dirac points from the same two bands emerges at 4.7 GPa. Due to the distinctive band structures compared with those of PtSe$_2$ and PtTe$_2$, the two types of Dirac points can coexist in PdTe$_2$ under proper pressure (4.7-6.1 GPa). The emergence of type-I Dirac cones and the disappearance of type-II Dirac ones are attributed to the increase/decrease of the energy of the states at $\Gamma$ and $A$ point, which have the anti-bonding/bonding characters of interlayer Te-Te atoms. On the other hand, we find that the superconductivity of PdTe$_2$ slightly decreases with pressure. The pressure-induced different types of Dirac cones combined with superconductivity may open a promising way to investigate the complex interactions between Dirac fermions and superconducting quasi-particles.