Admixture of an s-Wave Component to the d-Wave Gap Symmetry in High-Temperature Superconductors

Abstract

AbstractNeutron crystal-field spectroscopy experiments in optimally doped La1.81Sr0.15Ho0.04CuO4 and in slightly underdoped HoBa2Cu4O8 high-temperature superconductors are presented. By this bulk-sensitive technique, information on the gap function is obtained from the relaxation behaviour of crystal-field transitions associated with the Ho3+ ions which sit as local probes close to the superconducting copper-oxide planes. The relaxation data exhibit distinct anomalies at the pseudogap temperature T * where the pairing of the charge carriers occurs, as well as at the superconducting transition temperature T c where long-range phase coherence sets in. Our results are compatible with an unusual temperature dependence of the gap function in the pseudogap region (T c ≤ T ≤ T *), i.e., a breakup of the Fermi surface into disconnected arcs. Moreover, the relaxation data can only be modelled satisfactorily if the gap function of predominantly d-wave symmetry includes an s-wave component of the order of 20–25%. KeywordsFermi SurfaceRelaxation DataCopper IsotopeUnusual Temperature DependenceIntrinsic LinewidthThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.