Symmetry progression and possible polar metallicity in NiPS3 under pressure
Nathan C. Harms, T. Matsuoka, Subhasis Samanta, Amanda Clune, K. Smith, Amanda V. Haglund, Erxi Feng, Huibo Cao, Jesse S. Smith, David Mandrus, Heung‐Sik Kim, Zhenxian Liu, J. L. Musfeldt
Abstract
Abstract van der Waals solids are ideal platforms for the discovery of new states of matter and emergent properties under external stimuli. Under pressure, complex chalcogenides like M PS 3 ( M = Mn, Ni, Co, V) host sliding and structural transitions, insulator-to-metal transitions, the possibility of an orbitally-selective Mott state, piezochromism, and superconductivity. In this work, we bring together diamond anvil cell techniques, infrared and Raman scattering spectroscopies, and X-ray diffraction with a detailed symmetry analysis and first-principles calculations to uncover a series of high-pressure phases in NiPS 3 . Remarkably, we find five different states of matter between ambient conditions and 39 GPa—quite different than in the other M PS 3 materials. Even more strikingly, infrared spectroscopy and X-ray diffraction combined with a symmetry analysis reveal both metallicity and loss of the inversion center above ~23 GPa suggesting that NiPS 3 may be a polar metal with a P 3 m 1 space group under these conditions and P 1 symmetry under maximum compression. In addition to identifying a candidate polar metal ripe for further inquiry, we suggest that pressure may tune other complex chalcogenides into this elusive state.