Pressure-induced phase transition in La1-xSmxO0.5F0.5BiS2

Electrical resistivity measurements on La1-xSmxO0.5F0.5BiS2 (x = 0.1, 0.3, 0.6, 0.8) have been performed under applied pressures up to 2.6 GPa from 2 K to room temperature. The superconducting transition temperature T-c of each sample significantly increases at a Sm-concentration-dependent pressure P-t, indicating a pressure-induced phase transition from a low-T-c to a high-T-c phase. At ambient pressure, T-c increases dramatically from 2.8 K at x = 0.1 to 5.4 K at x = 0.8; however, the T-c values at P > P-t decrease slightly with x, and P-t shifts to higher pressures with Sm substitution. In the normal state, semiconducting-like behavior is suppressed, and metallic conduction is induced with increasing pressure in all of the samples. These results suggest that the pressure dependence of T-c for the BiS2-based superconductors is related to the lattice parameters at ambient pressure and enable us to estimate the evolution of T-c for SmO0.5F0.5BiS2 under pressure.