Pressure-induced enhancement of the superconducting transition temperature in La₂O₂Bi₃AgS₆

Charge density wave (CDW) instability is often found in phase diagrams of superconductors such as cuprates and certain transition-metal dichalcogenides. This proximity to superconductivity triggers the question on whether CDW instability is responsible for the pairing of electrons in these superconductors. However, this issue remains unclear and new systems are desired to provide a better picture. Here, we report the temperature-pressure phase diagram of a recently discovered BiS₂ superconductor La₂O₂Bi₃AgS₆, which shows a possible CDW transition at T^∗ ∼ 155 K and a superconducting transition at T_c ∼ 1.0 K at ambient pressure, via electrical resistivity measurements. Upon applying pressure, T^∗ decreases linearly and extrapolates to 0 K at 3.9 GPa. Meanwhile, T_c is enhanced and reaches maximum value of 4.1 K at 3.1 GPa, forming a superconducting dome in the temperature-pressure phase diagram.