By using a hydrostatic pressure, we have successfully tuned the ground stateand superconductivity in LaO0.5F0.5BiSe2 single crystals. It is found that,with the increase of pressure, the original superconducting phase with Tc about3.5 K can be tuned to a state with lower Tc, and then a new superconductingphase with Tc about 6.5 K emerges. Accompanied by this crossover, the groundstate is switched from a semiconducting state to a metallic one. Accordingly,the normal state resistivity also shows a nonmonotonic change with the externalpressure. Furthermore, by applying a magnetic field, the new superconductingstate under pressure with Tc about 6.5 K is suppressed, and the normal statereveals a weak semiconducting feature again. These results illustrate anon-trivial relationship between the normal state property andsuperconductivity in this newly discovered superconducting system.
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