Two high-pressure superconducting phases in pressurized optical semiconductor GaP

Pressure engineering in semiconductors leads to a variety of novel physical phenomena and has recently received considerable attention. Here, we report on pressure-induced superconductivity in III–V gallium phosphide (GaP), a commercially important semiconductor that exhibits excellent optical performance. We show that the emergence of superconductivity is accompanied by the concurrence of piezochromic transition and metallization and can be correlated to a structural transition from the cubic to orthorhombic phase. In line with the structural origin of superconductivity, the critical temperature Tc monotonically decreases with increasing pressure up to ~50 GPa. Moreover, the superconductivity could be preserved toward ambient pressure because of the irreversibility of the structural transition. Nevertheless, the superconducting transition displays evident broadening associated with the presence of amorphization in the depressurized sample. The synchronous evolution of the structural and electronic properties not only shows a vivid structure-property relationship but also could facilitate the exploration of novel functionalities by means of pressure treatment. III-V commercial optical semiconductor GaP crystalizes in either zincblende or wurtzite structure at ambient pressure. Zincblende GaP transforms into orthorhombic phase across a critical pressure during compression, accompanying piezochromic transition, metallization and superconductivity. Upon decompression, superconductivity could be preserved toward ambient pressure and displays broadening features due to amorphization. It reveals the presence of two high-pressure superconducting phases.