Chiral Superconductors

TL;DR

Chiral superconductivity is a topologically non-trivial quantum state with unique surface and vortex phenomena, with experimental evidence from various techniques supporting its realization in systems like Sr2RuO4 and UPt3.

Contribution

This paper reviews the current theoretical understanding and experimental evidence of chiral superconductors, highlighting key signatures and candidate materials such as Sr2RuO4 and UPt3.

Findings

Evidence of surface currents and chiral Majorana modes

Observation of Majorana states in vortex cores

Detection of half-flux quantum vortices

Abstract

Chiral superconductivity is a striking quantum phenomenon in which an unconventional superconductor spontaneously develops an angular momentum and lowers its free energy by eliminating nodes in the gap. It is a topologically non-trivial state and, as such, exhibits distinctive topological modes at surfaces and defects. In this paper we discuss the current theory and experimental results on chiral superconductors, focusing on two of the best-studied systems, Sr2RuO4, which is thought to be a chiral triplet p-wave superconductor, and UPt3, which has two low-temperature superconducting phases (in zero magnetic field), the lower of which is believed to be chiral triplet f-wave. Other systems that may exhibit chiral superconductivity are also discussed. Key signatures of chiral superconductivity are surface currents and chiral Majorana modes, Majorana states in vortex cores, and the possibility of half-flux quantum vortices in the case of triplet pairing. Experimental evidence for chiral superconductivity from muSR, NMR, strain, polar Kerr effect and Josephson tunneling experiments are discussed.