# Power-law Temperature Dependence of the Penetration Depth in a Topological Superconductor due to Surface States

## TL;DR

This paper investigates how surface states in a 3D topological superconductor cause a distinctive T^3 power-law temperature dependence in the magnetic penetration depth, offering a potential signature of topological superconductivity.

## Contribution

It introduces a theoretical model accounting for surface Majorana states' paramagnetic current, predicting a unique T^3 dependence in the penetration depth at low temperatures.

## Key findings

- Surface states induce a T^3 temperature dependence.
- Bulk remains fully gapped, distinguishing from nodal superconductors.
- Power-law behavior can serve as an indicator of topological superconductivity.

## Abstract

We study the temperature dependence of the magnetic penetration depth in a 3D topological superconductor (TSC), incorporating the paramagnetic current due to the surface states. A TSC is predicted to host a gapless 2D surface Majorana fluid. In addition to the bulk-dominated London response, we identify a $T^3$ power-law-in-temperature contribution from the surface, valid in the low-temperature limit. Our system is fully gapped in the bulk, and should be compared to bulk nodal superconductivity, which also exhibits power-law behavior. Power-law temperature dependence of the penetration depth can be one indicator of topological superconductivity.