  The pressure induced superconductivity and structural evolution for Bi2Se3
single crystal have been studied. The emergence of superconductivity with onset
transition temperature (Tc) about 4.4K is observed around 12GPa. Tc increases
rapidly to the highest 8.5K at 16GPa, decreases to 6.5K at 21GPa, then keep
almost constant. It is found that Tc versus pressure is closely related to the
carrier density which increases by more than two orders of magnitude from 2GPa
to 23GPa. High pressure synchrotron radiation measurements reveal structure
transitions occur around 12GPa, 20GPa, and above 29GPa, respectively. A phase
diagram of superconductivity versus pressure is obtained.
