Time-Reversal Symmetry Breaking and Intrinsic Magnus Force in Superfluid ³He-A

Abstract

The superfluid ³He is a condensate of spin-triplet p-wave Cooper pairs, with broken rotational symmetries in orbital and spin spaces as well as gauge symmetry. This multiple symmetry breaking gives rise to many unusual properties in the superfluid ³He. One of the superfluid phases called ³He-A breaks time-reversal symmetry. Although the time-reversal symmetry breaking (TRSB) is the most fundamental property, there has been no direct demonstration of TRSB so far. In this article, we demonstrate TRSB by discovering the intrinsic Magnus force experienced by an electron bubble moving in ³He-A. The intrinsic Magnus force allows for first direct detection of orientation of the angular momentum of Cooper pairs or chirality, which paves the way towards detailed investigations of unusual topological defects formed in the system with broken multiple symmetries.