Hydrostatic compression-driven lattice crossover, electronic metallization, and fermi surface reconstruction in few-layer 1T'-MoTe2

Abstract

This study investigates the structural, lattice dynamic, electronic, and Fermi surface evolution of exfoliated few-layer 1T'-molybdenum ditelluride (1T'-MoTe2) under hydrostatic pressure. Using a combination of atomic force microscopy, in-situ high-pressure micro-Raman spectroscopy, temperature-dependent four-probe electrical transport, and high-field magnetotransport within a diamond anvil cell, the material's phase behavior was systematically traced up to extreme pressures. Atomic force microscopy confirms uniform, atomically smooth flakes with an average thickness of 8.5 nm (approximately 12 layers). High-pressure Raman spectroscopy demonstrates a universal blue-shift of optical phonon modes and identifies a structural crossover near 4.8 GPa, characterized by the complete quenching of the  vibrational mode and a sharp reduction in mode pressure coefficients. Electrical transport measurements reveal a pressure-induced transition from a semiconducting state with a 42.1 meV thermal activation energy to a fully metallic state at 8.2 GPa, displaying Fermi-liquid quadratic resistance scaling at low temperatures under 14.5 GPa. Furthermore, high-field magnetotransport at 12.8 GPa unveils a large, non-saturating magnetoresistance reaching 420% at 9 T alongside distinct Shubnikov–de Haas quantum oscillations. Fast Fourier Transform analysis resolves fundamental oscillation frequencies at 142 T and 285 T, corresponding to a light cyclotron effective mass of 0.12 electron masses. These findings establish hydrostatic pressure as a powerful knob for tuning electronic band structures and Fermi surface topology in transition metal dichalcogenides, providing critical insights for the development of strain-engineered quantum devices and phase-change electronics.