A new mechanism of superconductivity in semiconductors and semimetals based on the metallic phase of the exciton was proposed by Abrikosov. He estimated the critical temperature for CuCl to be of order 100° K by employing the weak coupling BCS formula. It is shown here that the strong-coupling limit is more appropriate and that $T_c$ is then estimated to be of the order 1° K.

• Received 24 May 1978

DOI:https://doi.org/10.1103/PhysRevB.20.1020