Symmetry, Sound, and the Quest for Chiral Superconductors

Abstract

The confirmation of a bulk, topological superconductor is a central goal of modern quantum materials research. Despite decades of searching, no confirmed examples yet exist. A primary difficulty is that most experimental signatures of topological superconductivity are ambiguous and indirect. I review efforts to narrow the search for a chiral topological superconductor using measurements of elastic moduli. In principle, these experiments can provide unambiguous thermodynamic evidence for multi-component superconductivity---a pre-requisite for chiral superconductivity in 2D and quasi-2D materials. Despite the potential strength of this program, the results are still negative. I provide a pedagogical introduction to multi-component order parameters, chiral topological superconductivity, and how superconducting order parameters couple to strain. I discuss ongoing efforts in heavy fermion, iron pnictide, and Kagome superconductors, and suggest routes for speeding up the search process, as well as other experimental tools that should be developed for the pursuit of this goal.