Pressure-tuned structure and electric transport properties in violet phosphorus

Violet phosphorus, as a kind of two-dimensional material, has become an excellent candidate for optoelectronic devices as it makes up for the drawbacks of black phosphorus applications. This study explores the structural and electrical properties of violet phosphorus under high-pressure conditions. Two structure phase transitions are revealed by the spectra and electromagnetic transport measurements. At $\ensuremath{\sim}8$ GPa, a structural transition from monoclinic to A7 phase is observed with the appearance of superconductivity. The transition from the A7 phase to the simple cubic phase starts at $\ensuremath{\sim}13$ GPa and completes after $\ensuremath{\sim}30$ GPa at low temperatures. In addition, the band gap of violet phosphorus decreases linearly with the increase of pressure until it disappears after the transition to the A7 phase. The anisotropic upper magnetic field of superconductivities in A7 and simple cubic phases showed the relative crystal orientations of the high-pressure phases compared with initial violet phosphorus crystal phase.