Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1819482 | Physica C: Superconductivity and its Applications | 2008 | 4 Pages |
Abstract
The 2D Hubbard model having the 2nd- and 3rd-neighbor transfer energies tâ² and tâ³ is investigated by use of the variational Monte Carlo method. At the nearly optimal doping with on-site Coulomb energy U = 6 (energy unit is t) the condensation energy Econd for the d-wave superconductivity (SC) is computed for lattices of sizes from 10 Ã 10 to 28 Ã 28 with the aim to get its bulk-limit value. tâ³ is fixed at âtâ²/2. Outside and in the neighborhood of the SDW region of -0.16 ⩽ tâ²Â ⩽ â0.08 the SC Econd dominates over the SDW Econd. At tâ²Â = â0.05 and â0.10 we obtained a definitely finite bulk-limit SC Econd of the order of the experimental value for YBCO. At tâ²Â = 0 Econd nearly vanishes. For tâ²Â ⩽ -0.18, the SC Econd strongly oscillates as a function of the lattice size, when periodic boundary conditions (b.c.'s) are imposed to both axes. In the case of periodic and anti periodic b.c.'s, a finite bulk-limit value is obtained at tâ²Â = â0.22. Econd tends to vanish with further decrease of tâ². With our results the SC of LSCO is understandable with tâ²â¼â0.10. The tâ² values of Hg1201, Tl2201 and Na-CCOC seem close to â0.20 so that they locate in the boundary zone of SC indicated in the present work. Slightly larger U improves the situation by increasing Econd.
Keywords
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Condensed Matter Physics
Authors
K. Yamaji, T. Yanagisawa, M. Miyazaki, R. Kadono,