Speaker: James A. Sauls

Host: Ruslan Prozorov

Title: The Left Hand of the Electron

Abstract:

Sixty plus years ago parity violation by the weak force was demonstrated in experiments led by Chien-Shiung Wu on the asymmetry of electron currents emitted in the beta decay of polarized 60Co. The asymmetry reflects two broken symmetries - mirror reflection and time reversal, the latter imposed by an external magnetic field. The same year Bardeen, Cooper, and Schrieffer published the celebrated BCS theory of superconductivity, and soon thereafter, P. W. Anderson and P. Morel proposed that the ground-state of liquid 3He was possibly a BCS condensate of chiral p-wave Cooper pairs, exhibiting spontaneously broken mirror reflection and time-reversal symmetries. Indeed the high-pressure phase, superfluid 3He-A, discovered in 1972, is the realization of the Anderson-Morel state. Definitive proof that 3He-A spontaneously breaks mirror and time-reversal symmetry came 41 years later with the observation an anomalous Hall effect for electrons moving in superfluid 3He-A.1 I discuss this discovery and the theory of the anomalous Hall effect for electrons moving in the chiral phase of 3He.2 I explain the origin of the transverse force on an electron moving in the chiral vacuum, and dis- cuss implications of the theory and its extension to anomalous Hall transport for the broad class of chiral superconductors, including candidates for chiral superconductivity: Sr2RuO4, UPt3, URu2Si2 UTe2 etc.3

1. H. Ikegami, Y. Tsutsumi, & K. Kono, Chiral Symmetry in Superfluid 3He-A, Science 341, 59–62 (2013)

2. O. Shevtsov & J. A. Sauls, Electrons & Weyl Fermions in Superfluid 3He-A, Phys. Rev. B 94, 064511 (2016)

3. V. Ngampruetikorn & J. A. Sauls, Anomalous Thermal Hall Effect in Chiral Superconductors, Phys. Rev. Lett. 124, 157002 (2020)

† Research supported by NSF grant DMR-1508730.