Symmetry breaking and topology in superfluid 3He

Quantum phenomena observed in the p-wave superfluid 3He are intimately related to symmetry breaking and topology, and their understanding has significant implications not only on condensed matter physics but also on particle physics and cosmology. In this talk, I will show novel phenomena arising from symmetry breaking and non-trivial topology of superfluid 3He investigated by electrons trapped below a free surface. In particular, I will present the first direct demonstration of time-reversal symmetry breaking in one of the superfluid phases called 3He-A by showing that electrons immersed in superfluid 3He-A exhibit an anomalous Hall effect [1,2] and the direct observation of Majorana surface states formed at a free surface of topological 3He-B phase [3-5].