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

By means of first-principles density-functional theory calculations, we investigate the role of hydrostatic pressure in the electronic structure of the Td (Pmn21) and 1T '' (Pm) phases of the Weyl semimetal Mo0.5W0.5Te2, 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 the 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 Mo0.5W0.5Te2 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 Td (1T '') 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 '' 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.

Automated summary

This study investigates the role of hydrostatic pressure in the electronic structure of Mo0.5W0.5Te2 in the Td and 1T'' phases, showing changes in the distribution of Weyl points under pressure and structural phase transitions. The results suggest a complex evolution of Weyl points with pressure, with different behaviors in the Td and 1T'' phases.