FAR-INFRARED TRANSMISSION STUDY OF SINGLE-CRYSTAL BI2SR2CA1CU2OX SUPERCONDUCTORS

We report the infrared transmission of free-standing single crystals of the high-temperature superconductor Bi2Sr2Ca1Cu2Ox, at temperatures between 25 and 300 K and at frequencies covering the range of 1.5kBTc Latin small letter h with stroke<12kBTc. The normal-state Drude relaxation rate follows a linear temperature dependence Latin small letter h with stroke/=3kBT. In the superconducting state there is no indication of a transmission peak, which characterizes a superconducting gap in the optical conductivity. We suggest that a strong pair-breaking interaction is responsible for this null result. © 1990 The American Physical Society.