Superconducting gap and excitonic mechanism of high-Tc superconductors

✍ Scribed by J Tanaka; K Kamiya; M Shimada; M Shimizu; M Tanaka; Y Tanaka

• Publisher: Elsevier Science
• Year: 1987
• Weight: 154 KB
• Volume: 148
• Category: Article
• ISSN: 0378-4363
• DOI: 10.1016/0378-4363(87)90271-3

✦ Synopsis

The high-T c mechanism of the oxide superconductors has been studied by measuring optical reflection spectra over a wide wavelength range at various temperatures. The superconducting gap was found at 225 cm L in Ba2YCu3068 which give the value 3.57 of 2A/k 8T c. Two gaps were found in Lai 85Sr0 ~sCuO 4 at 115 and 70 cm 1, which correspond to the values 4.11 and 2.5 of 2A/k B T c. We found that the superconducting gaps are reasonably predicted by the BCS theory with experimentally determined exciton energy and transition temperatures. The origin of the exciton, which couples with electrons, is the charge resonance transition within the layer of the mixed valence Cu-O-Cu plane.