Magnetic Penetration Depth in Unconventional Superconductors

TL;DR

This review discusses how magnetic penetration depth measurements reveal detailed information about the pairing mechanisms, gap structures, and magnetic properties of unconventional superconductors, enhancing understanding of their complex behaviors.

Contribution

It provides a comprehensive overview of how field, temperature, and orientation-dependent penetration depth measurements can be used to study various unconventional superconducting states and phenomena.

Findings

Field-dependent measurements reveal surface Andreev bound states.

Orientation-dependent measurements explore anisotropic and multi-gap superconductors.

Penetration depth analysis aids in understanding vortex dynamics and magnetic impurities.

Abstract

This topical review summarizes various features of magnetic penetration depth in unconventional superconductors. Precise measurements of the penetration depth as a function of temperature, magnetic field and crystal orientation can provide detailed information about the pairing state. Examples are given of unconventional pairing in hole- and electron-doped cuprates, organic and heavy fermion superconductors. The ability to apply an external magnetic field adds a new dimension to penetration depth measurements. We discuss how field dependent measurements can be used to study surface Andreev bound states, nonlinear Meissner effects, magnetic impurities, magnetic ordering, proximity effects and vortex motion. We also discuss how penetration depth measurements as a function of orientation can be used to explore superconductors with more than one gap and with anisotropic gaps. Details relevant to the analysis of penetration depth data in anisotropic samples are also discussed.