Competitive multiple phase transitions and distinct superconducting states in a R e 3 G e 7 single crystal under hydrostatic pressure

We report the growth and physical properties of high-quality needle-shaped $\mathrm{R}{\mathrm{e}}₃\mathrm{G}{\mathrm{e}}₇$ single crystal with various characterizations. It exhibits a gapped metal-insulator (MI)-like phase transition with evident Shubnikov--de Haas oscillation of low-$T$ electrical resistivity. The superconducting phase diagram was revisited by measuring the electrical resistivity in a cubic anvil cell (CAC) under various hydrostatic pressures up to 12 GPa. Unlike the results of single crystals in a diamond anvil cell (DAC) and polycrystalline in CAC, the gapped MI-like phase transition of single-crystal $\mathrm{R}{\mathrm{e}}₃\mathrm{G}{\mathrm{e}}₇$ evolves into three charge density wave (CDW)-like ones, which are reduced gradually by applied pressure and then collapse at several critical pressures; approaching the CDW-like quantum criticality, two distinct superconducting phases emerge and transit from one to another in a narrow pressure range; the significant increase in superconducting width indicates their strong competition. By combining density functional theory calculations, the origin of the melting MI-like transition caused by pressure and Ga doping, as well as the competitive CDW-like phase transitions and distinct superconductivity, are discussed.