C-axis Penetration Depth and Inter-layer Conductivity in the Thallium Based Cuprate Superconductors

TL;DR

This study investigates the c-axis Josephson plasmon and inter-layer conductivity in Tl-based cuprate superconductors using infrared spectroscopy, revealing weak coherent quasiparticle contributions along the c-axis even below Tc.

Contribution

It provides new measurements of Josephson plasma frequencies in Tl2201 and Tl2212 and analyzes their implications for inter-layer coherence in high-Tc cuprates.

Findings

Josephson plasma frequencies at 27.8 and 25.6 cm-1 in Tl2201 and Tl2212

Absence of a maximum in c-axis conductivity below Tc

Weak or absent coherent quasiparticle contribution along the c-axis

Abstract

The c-axis Josephson plasmon in optimally doped single-layer and bi-layer high Tc cuprates Tl2201 and Tl2212 have been investigated using infrared spectroscopy. We observed the plasma frequencies for these two compounds at 27.8 and 25.6 cm-1 respectively, which we interpret as a Josephson resonance across the TlO blocking layers. No maximum in the temperature dependence of the c-axis conductivity was observed below Tc, indicating that even in the superconducting state a coherent quasi-particle contribution to the c-axis conductivity is absent or very weak, in contrast to the behaviour of the ab-plane conductivity.