Nodeless spin triplet superconducting gap in Sr2RuO4

TL;DR

This study uses STM tunneling spectroscopy to reveal a nodeless, fully opened spin triplet superconducting gap in Sr2RuO4, consistent with weak coupling BCS theory and indicating odd parity superconductivity.

Contribution

It provides direct experimental evidence of a nodeless, isotropic superconducting gap in Sr2RuO4, supporting the odd parity triplet pairing hypothesis.

Findings

Superconducting gap Δ=0.28 meV disappears at T_c=1.5 K

Gap is consistent with weak coupling BCS theory

Superconductivity exhibits a fully isotropic, nodeless gap

Abstract

We report on tunneling spectroscopy measurements using a Scanning Tunneling Microscope (STM) on the spin triplet superconductor Sr2RuO4. We find a negligible density of states close to the Fermi level and a fully opened gap with a value of $\Delta$=0.28 meV, which disappears at T$_c$ = 1.5 K. $\Delta$ is close to the result expected from weak coupling BCS theory ($\Delta_0$=1.76kBT$_c$ = 0.229 meV). Odd parity superconductivity is associated with a fully isotropic gap without nodes over a significant part of the Fermi surface.