Tunneling and infrared measurements of the energy gap in the high-critical-temperature superconductor Y-Ba-Cu-O

Abstract

We have measured the superconducting energy gap Δ of high-critical-temperature ($T_c$∼90 K) ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{9\mathrm{-}\mathrm{y}}$ samples using tunneling and infrared techniques. From our tunneling data, we place limits on the reduced superconducting energy gap of 3.7$k_B$$T_c$