A pressure induced semiconductor-semimetal phase transition on tungsten diselenide has been studied using in situ electrical resistivity measurement and first-principles calculation under high pressure. The experimental results indicate that the phase transition takes place at 38.1 GPa. The first-principles calculations performed by CASTEP code based on the density functional theory illustrate that the indirect band gap of WSe 2 vanishes at 35 GPa, which results in an isostructural phase transition from semiconductor to semimetal in WSe 2 . According to the pressure dependence of partial density of states, the semimetallic character of WSe 2 is mainly caused by W-Se covalent bonding rather than van der Waals bonding.

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The electrical transport behavior of SnS under high pressure has been investigated by the temperature dependence of electrical resistivity measurement, the in situ Hall-effect measurement, and the first-principle calculation. The experimental results show that SnS undergoes a semiconductor to semimetal transition at ∼10.3 GPa, and this transition is further substantiated by the band-structure calculation. The total and partial density of states predict that the semimetal character of SnS is attributed to the enhanced coupling of Sn-5s, Sn-5p, and S-3p states with application of pressure. In addition, dramatic changes in electrical transport parameters such as the electrical resistivity, the carrier concentration, and the carrier mobility are observed at 12.6 GPa, which are correlated to the pressure-induced Pnma-Cmcm structural phase transition.

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