Superconductivity in the doped topological insulator Cu$_x$Bi$_2$Se$_3$   under high pressure
  We report a high-pressure single crystal study of the topological superconductor Cu$_x$Bi$_2$Se$_3$. Resistivity measurements under pressure show superconductivity is depressed smoothly. At the same time the metallic behavior is gradually lost. The upper critical field data $B_{c2}(T)$ under pressure collapse onto a universal curve. The absence of Pauli limiting and the comparison of $B_{c2}(T)$ to a polar state function point to spin-triplet superconductivity, but an anisotropic spin-singlet state cannot be discarded completely. 
T. V. Bay, T. Naka, Y. K. Huang, H. Luigjes, M. S. Golden and A. de   Visser
cond-mat.supr-con