Prediction of a novel robust superconducting state in TaS2 under high pressure

In this work, we performed first-principles structure-searching calculations to investigate the behaviors of tantalum disulfide (TaS2) under compression. Beside the well-known 1T and 2H phases at ambient pressure, our results reveal two new phases with the space group of C2/m (in the pressure range of 27-59 GPa) and I4/mmm (stable above 59 GPa). The C2/m and I4/mmm phases adopt three-dimensional covalent framework structures possessing highly eight-fold and ten-fold coordinated Ta, respectively. Strikingly, we observed an unusual superconductor-metal-superconductor transition in TaS2 with the increase of pressure. The predicted C2/m structure exhibits metallic character, while all the other low-pressure (1T and 2H) and high pressure (I4/mmm) phases of TaS2 show superconductivity under pressure. A robust superconductivity of I4/mmm-TaS2 is predicted up to a maximum transition temperature of 7.62 K at 60 GPa and can be stable up to 200 GPa. Our findings, therefore, provide important information to further understand the intrinsic physics of pressure-driven behaviors in transition metal dichalcogenides and related materials.