The metal-semiconductor-metal transition of 2M-WSe2 under high pressure

Abstract

High pressure has been an effective method to induce exotic physical properties and novel phenomena on layered transition metal dichalcogenides (TMDs). In this study, we investigated the electrical transport properties and structural evolution of 2M-WSe2, a newly discovered structural TMD, under pressure up to 88.0 GPa using diamond anvil cells (DAC). At relatively low pressure, samples exhibit an initial metallic state with the emergence of superconductivity, 4.2 K, at approximately 3.1 GPa. With increasing pressure, superconductivity diminishes, and an unexpected metallic-to-semiconducting transition (MST) becomes evident near 12.5 GPa. Comprehensive analysis of XRD data unveils that the MST is accompanied by pressure-induced modulation of the interlayer structure to a monoclinic P21/m phase. Combined with Hall effect measurements, the MST can be attributed to the decrease in hole-type carrier concentration resulting from the phase transition. The P21/m phase initially exhibits semiconducting characteristics but rapidly evolves into an exceptional metal as compression continues. Identifying this rare metal-semiconductor-metal transition in TMDs marks a significant recognition, further enhancing the insight into the structure-dependent modulation of electronic properties in layered materials.