Polar Kerr effect studies of time reversal symmetry breaking states in heavy fermion superconductors

•Polar Kerr effect (PKE) probes broken time-reversal symmetry (TRS) in superconductors.•Absence of PKE below Tc in CeCoIn5 is consistent with dx2-y2 order parameter symmetry.•PKE in the B phase of the multiphase superconductor UPt3 agrees with an E2u model.•Data on URu2Si2 show broken TRS and additional structure in the superconducting state. The connection between chiral superconductivity and topological order has emerged as an active direction in research as more instances of both have been identified in condensed matter systems. With the notable exception of 3He-B, all of the known or suspected chiral – that is to say time-reversal symmetry-breaking (TRSB) – superfluids arise in heavy fermion superconductors, although the vast majority of heavy fermion superconductors preserve time-reversal symmetry. Here we review recent experimental efforts to identify TRSB states in heavy fermion systems via measurement of polar Kerr effect, which is a direct consequence of TRSB.