Pressure-induced structural transition, metallization, and topological superconductivity in PdSSe

TL;DR

This paper predicts how applying pressure induces structural changes, metallization, and topological superconductivity in PdSSe, revealing complex phase transitions and electronic state evolutions in this transition metal dichalcogenide.

Contribution

It provides a theoretical analysis of pressure-driven structural and electronic transitions in PdSSe, including the emergence of topological superconductivity and symmetry-breaking cubic phases.

Findings

Structural phase transitions from orthorhombic to cubic occur under pressure.

Electronic structure changes from semiconductor to semimetal with pressure.

Cubic phase exhibits topologically nontrivial Weyl and high-fold Fermions.

Abstract

Pressure not only provides a powerful way to tune the crystal structure of transition metal dichalcogenides (TMDCs) but also promotes the discovery of exotic electronic states and intriguing phenomena. Structural transitions from the quasi-two-dimensional layered orthorhombic phase to three-dimensional cubic pyrite phase, metallization, and superconductivity under high pressure have been observed experimentally in TMDCs materials PdS2 and PdSe2. Here, we report a theoretical prediction of the pressure-induced evolutions of crystal structure and electronic structure of PdSSe, an isomorphous intermediate material of the orthorhombic PdS2 and PdSe2. A series of pressure-induced structural phase transitions from the layered orthorhombic structure into an intermediate phase, then to a cubic phase are revealed. The intermediate phase features the same structure symmetry as the ambient orthorhombic phase, except for drastic collapsed interlayer distances and striking changes of the coordination polyhedron. Furthermore, the structural phase transitions are accompanied by electronic structure variations from semiconductor to semimetal, which are attributed to bandwidth broaden and orbital-selective mechanisms. Especially, the cubic phase PdSSe is distinct from the cubic PdS2 and PdSe2 materials by breaking inversion and mirror-plane symmetries, but showing similar superconductivity under high pressure, which is originated from strong electron-phonon coupling interactions concomitant with topologically nontrivial Weyl and high-fold Fermions. The intricate interplay between lattice, charge, and orbital degrees of freedom as well as the topologically nontrivial states in these compounds will further stimulate wide interest to explore the exotic physics of the TMDCs materials.