Pressure-induced metallization and electronic transition in a two-dimensional ferroelastic semiconductor of Nb₂SiTe₄...

Nb₂SiTe₄, a representative two-dimensional (2D) ferroelastic semiconductor, becomes research focus due to its high carrier mobility, ambipolar carrier transport, exceptional ferroelasticity and third harmonic generation response, rendering potential applications in ambipolar transistors, mid-infrared (MIR) detection, controllable electronic devices and tunable anisotropic all-optical devices. In this work, high-pressure lattice vibrational and electrical transport characteristics of Nb₂SiTe₄ were comprehensively explored up to 37.1 GPa using a diamond anvil cell (DAC) in conjunction with in situ Raman spectroscopy and electrical conductivity measurements in different hydrostatic environments. Upon non-hydrostatic pressurization, Nb₂SiTe₄ underwent metallization at 5.5 GPa owing to the rapid compression of the interlayer distance, followed by an electronic transition at 21.6 GPa triggered by the enhanced electron-phonon coupling. Nevertheless, the metallization and electronic transition of the specimen were delayed by ∼2.0 GPa under hydrostatic conditions due to the influence of deviatoric stress. Upon decompression to ambient conditions, the resumable Raman spectra and semiconducting characteristics elucidated the reversibility of the phase transition with the existence of residual stress in different hydrostatic environments. Our systematic high-pressure research studies on Nb₂SiTe₄ not only advance the in-depth understanding of its physicochemical behaviours in other 2D ferroelastic semiconductors but are also beneficial in steering its underlying applications in electronic and photonic devices.