Layer reconstruction, collapse and metallization of van der Waals bonded ZrS2 under high pressure

Abstract

In contrast to two-dimensional (2D) monolayer materials, van der Waals layered transition metal dichalcogenides exhibit rich polymorphism, making them promising candidates for novel superconductors, topological insulators, and high-performance electrochemical catalysts. Here, we combine Raman scattering, electrical conductivity, and synchrotron X-ray diffraction measurements to reveal a series of phase transitions in van der Waals layered ZrS2, driven by the formation of a distorted metastable structure under pressure. Unlike layered sliding observed in archetypal MoS2, ZrS2 undergoes a dramatic structural reconstruction, rearranging the original ZrS6 octahedra into ZrS8 cuboids at 5.5 GPa, leading to an abrupt 8.8% volume reduction. The unique cuboids coordination of Zr atoms in the single-layer is thermodynamically metastable and collapses to a partially disordered phase at 17.4 GPa, and ultimately metallize above 30.0 GPa. Decompressing metallic ZrS2 restores its semiconductor properties. These complex structural transitions present the highly tunable electronic properties of compressed ZrS2 with possible implications for optoelectronic devices.