Volume 50, Number 6, June II 2000
|Page(s)||782 - 788|
|Section||Condensed matter: electronic structure, electrical, magnetic, and optical properties|
|Published online||01 September 2002|
Phase transition between d-wave and anisotropic s-wave gaps in high-temperature oxides superconductors
Department of Physics,
Pusan National University - Pusan 609-735, Korea
2 Laboratoire de Physique des Solides, Université Paris-Sud Centre d'Orsay, 91405 Orsay Cedex, France (Unit associated to the CNRS.)
3 Institute for Solid State Physics, University of Tokyo 7-22-1 Roppongi, Minato-ku, Tokyo, Japan
Accepted: 25 April 2000
We numerically study models for superconductivity with two interactions: due to antiferromagnetic (AF) fluctuations and due to phonons, in a weak coupling approach to the high-temperature superconductivity. The nature of the two interactions is considerably different: is positive and sharply peaked at (,) while is negative and peaked at (0,0) due to weak phonon screening. The superconductivity is mainly induced by . The positive interaction (AF) is not effective in superconductivity, but important to give d-wave superconductivity. The gap order parameter is constant (s-wave) at an extremely overdoped region and it becomes anisotropic as doping is reduced. Then there exists a first-order phase transition between anisotropic s-wave and d-wave gaps as doping is reduced further. These results are qualitatively in agreement with preceding works; they should be modified in the strongly underdoped region by the presence of antiferromagnetic pseudogap due to the fluctuations.
PACS: 74.20.-z – Theories and models of superconducting state / 74.20.Fg – BCS theory and its development
© EDP Sciences, 2000
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