Interlayer Josephson couplings in Hg-based multi-layered cuprates

Abstract

Infrared reflectivity spectra of the multilayered HgBa2Can-1CunO2n+2+δ(n=2,3,4,and5) are measured. Optical plasma modes associated with the Josephson coupling between CuO2 planes within a multilayer appear below Tc in the c-axis component of the reflectivity spectrum. For the bilayer and trilayer compound an optical Josephson plasma mode appears at unprecedentedly high frequency, ∼700–800cm-1, below Tc. The plasma frequencies appreciably decrease in four- and five-layer compounds which indicates the suppression of superconducting order in the inner CuO2 planes, consistent with the result of NMR experiment.