Infrared studies of superconducting MgB2 thin films

Abstract Reflectance of superconducting MgB 2 thin films ( T c ≈35 K) has been measured in a broad spectral range from 30 to 110,000 cm −1 . A typical plasma edge with a reflectance minimum at 15,000 cm −1 has been found. In the far-infrared region we observe a pronounced rise of the reflectance below 60 cm −1 , which appears below T c and can be associated with superconducting state. The temperature-dependent complex conductivity at infrared frequencies has been determined. The real and imaginary parts of the conductivity below T c show a temperature evolution, which is characteristic for superconducting gap opening (decrease in σ 1 and rise in σ 2 ).