Pressure-induced creation and annihilation of Weyl points in Td- and 1T"-Mo0.5W0.5Te2

TL;DR

This study uses first-principles calculations to explore how hydrostatic pressure affects Weyl points in Mo0.5W0.5Te2, revealing pressure-driven creation and annihilation of Weyl points and phase stability changes.

Contribution

It provides detailed insights into pressure-induced topological and structural transitions in Mo0.5W0.5Te2, including Weyl point dynamics and phase stability analysis.

Findings

Weyl points increase to 44 (36) with pressure via pair creation up to 20 GPa

Pair annihilation reduces Weyl points to 16 at 45 GPa

Phase transition from 1T'' to Td occurs at 7.5 GPa

Abstract

By means of first-principles density-functional theory calculations, we investigate the role of hydrostatic pressure on the electronic structure of Td (Pmn21 ) and 1T" (Pm) phases of Weyl semimetal Mo0.5 W0.5 Te2 , which is a promising material for phase-change memory technology and superconductivity. We particularly focus on changes occurring in the distribution of the gapless Weyl points (WPs) within 0 to 45 GPa pressure range. We further investigate the structural phase transition and lattice dynamics of the Td and 1T" phases within the aforementioned pressure range. Our calculations suggest that both the Td and 1T" phases of Mo0.5 W0.5 Te2 host four WPs in their full Brillouin zone at zero pressure. The total number of WPs increases to 44 (36) with increasing pressure via pair creation up to 20 (15) GPa for the T d (1T 00 ) phase, and beyond this pressure pair annihilation of WPs starts occurring leaving only 16 WPs at 45 GPa in both phases. The enthalpy versus pressure data reveal that the 1T 00 phase is more favorable below the critical pressure of 7.5 GPa, however, beyond this critical pressure the Td phase becomes enthalpically favorable. We also provide the calculated x-ray diffraction spectra along with the calculated Raman- and infrared-active phonon frequencies to facilitate the experimental identification of the studied phases.