Negative U-centers and defect superconductivity

✍ Scribed by S. Dzhumanov; B. Yavidov; N.A. Makhmudov

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 117 KB
• Volume: 21
• Category: Article
• ISSN: 0749-6036
• DOI: 10.1006/spmi.1996.0390

✦ Synopsis

A connection between the formation of defect bipolarons (i.e. U-centers or U-bipolarons) and superconductivity in high-T c superconductors (HTSC) is considered in two pairing limits of carriers in real r -and k-spaces. The irrelevance of r -space U-bipolarons to superconductivity is motivated. It is shown that the formation of k-space U-bipolarons and their subsequent attractive single particle and pair condensation lead to depressed (in comparison with lattice bipolarons) superconductivity due to a large mass of such U-bipolarons. It is argued that the coexistence of k-space lattice bipolarons and r -space U-bipolarons leads to the shift of the maximum of the concentration dependence T c (n) to higher carrier concentrations, in accordance with the observations in HTSC.