LAUSR

Abstract High-pressure in situ angle dispersive X-ray diffraction (ADXRD) measurements were performed on the charge-density-wave (CDW) material In 4 Se 3 up to 48.8 GPa. Pressure-induced structural changes were observed at 7.0 and 34.2 GPa, respectively. Using the CALYPSO methodology, the first high-pressure phase was solved as an exotic Pca 2 1 structure. The compressional behaviors of the initial Pnnm and the Pca 2 1 phases were all determined. Combined with first-principle calculations, we find that, unexpectedly, the Pnnm phase probably experiences twice electronic topological transitions (ETTs), from the initial possible CDW state to a semimetallic state at about 2.3 GPa and then back to a possible CDW state at around 3.5 GPa, which was uncovered for the first time in CDW systems. In the both possible CDW states, pressure provokes a decrease of band-gap. The observation of a bulk metallic state was ascribed to structural transition to the Pca 2 1 phase. Besides, based on electronic band structure calculations, the thermoelectric property of the Pnnm phase under compression was discussed. Our results show that pressure play a dramatic role in tuning In 4 Se 3 's structure and transport properties.