c-axis phase coherence and spin fluctuations in cuprates

Université Libre de Bruxelles - CP-232, Blvd du Triomphe, B-1050 Brussels, Belgium

Received: 5 June 2000
Accepted: 10 April 2001

Abstract

There is a consensus that superconductivity (SC) in cuprates is two-dimensional. It is widely believed that the long-range phase coherence appears at T_c due to the Josephson coupling between SC CuO₂ (bi-, tri-, ...) layers. Recent T_c and resistivity measurements in Tl₂Ba₂CaCu₂O₈ as a function of applied pressure (Salvetat J.-P. et al., Europhys. Lett., 52 (2000) 584) show that the interlayer Josephson-coupling mechanism does not fit the data. Here we analyze data obtained in Andreev reflection, neutron scattering, microwave, muon spin relaxation, tunneling and resistivity measurements performed on different cuprates, mainly, on YBa₂Cu₃O, Bi₂Sr₂CaCu₂O and LaSr_xCuO. The analysis of the data shows that the long-range phase coherence in the cuprates intimately relates to antiferromagnetic interactions along the c-axis. At the same time, it seems that the in-plane mechanism of SC has no or little relations to the magnetic interactions along the c-axis.