Chiral Symmetry Breaking in Superfluid 3He-A

Spontaneous symmetry breaking is an important concept in many branches of physics. In helium-3 (He-3), the breaking of symmetry leads to the orbital chirality in the superfluid phase known as He-3-A. Chirality is a fundamental property of He-3-A, but its direct detection has been challenging. We report direct detection of chirality by transport measurements of electrons trapped below a free surface of He-3-A. In particular, we observed the so-called intrinsic Magnus force experienced by a moving electron; the direction of the force directly reflected the chirality. We further showed that, at the superfluid transition, the system selected either right-or left-handed chirality. The observation of such selection directly demonstrates chiral symmetry breaking.