Interplay of Phase Fluctuations and Electronic Excitations in High-Temperature Superconductors — A Monte Carlo Simulation

Abstract

Although the binding of electrons into Cooper pairs is necessary in forming the superconducting state, its remarkable properties like zero resistance and perfect diamagnetism require long-range phase coherence among the pairs as well. When coherence is lost due to thermal fluctuations of the phase at the transition temperature T _c, pairing remains, together with short-range phase correla- tions. In conventional metals, Cooper pairs with short-range phase coherence are destroyed less than 1K above T _c. In underdoped high-T _c copper oxides, however there is spectroscopic evidence for some form of pairing up to a temperature T*, which is more than 100K above T _c [1-3]. How this pairing above T _c and Cooper-pair formation are related is one of the most challenging problems in high-T _c superconductivity. Here we report first numerical results of the dynamical properties of a model Hamiltonian which explicitly takes these phase-fluctuations into account by using a new Monte-Carlo (MC) technique. The phases are thereby controlled by a classical XY-action.