Effect of Interband Transitions on the c axis Penetration Depth of Layered Superconductors

TL;DR

This paper investigates how interband electronic transitions influence the c-axis penetration depth in layered superconductors, revealing their dominance in low-temperature behavior and their connection to pseudogap phenomena.

Contribution

It introduces the impact of interband transitions on the temperature dependence of the c-axis penetration depth, highlighting their significance when interplane hopping is small.

Findings

Interband transitions can dominate low-temperature penetration depth behavior.

The penetration depth may become flat even with a d-wave gap due to interband effects.

Connections between interband effects and pseudogap phenomena are established.

Abstract

The electromagnetic response of a system with two planes per unit cell involves, in addition to the usual intraband contribution, an added interband term. These transitions affect the temperature dependence and the magnitude of the zero temperature c-axis penetration depth. When the interplane hopping is sufficiently small, the interband transitions dominate the low temperature behaviour of the penetration depth which then does not reflect the linear temperature dependence of the intraband term and in comparison becomes quite flat even for a d-wave gap. It is in this regime that the pseudogap was found in our previous normal state calculations of the c-axis conductivity, and the effects are connected.