Condensed Matter Seminar: "The Left Hand of the Electron in Superfluid 3He-A"
(sign-up)Jim Sauls, Northwestern University
|Sponsor:||Physics - Condensed Matter|
Sixty years ago parity violation by the weak force was demonstrated in experiments led by C. S. Wu on the asymmetry of electron currents emitted in the beta decay of 60Co with respect to mirror reflection. The same year Bardeen, Cooper and Schrieffer published the celebrated BCS theory of superconductivity. As a tribute to those discoveries I present experimental and theoretical results on spontaneously broken time-reversal and parity violation in what is arguably the most symmetric phase of condensed matter in nature, that of liquid 3He. Helium remains liquid down to absolute zero and is the purest form of matter in nature. The light isotope 3He undergoes BCS condensation below 2 x 10-3 Kelvin. Under a wide range of conditions the broken symmetry ground state is a chiral superfluid which spontaneously breaks time-reversal and mirror symmetries. Electrons impressed into liquid 3He form a self-trapped negative ion, an “electron bubble” with an effective mass M ≈ 100m3 and an ionic radius R ≈ 2nm. An anomalous Hall effect for electron transport in superfluid 3He was reported by the Kono laboratory at RIKEN.1 These experiments provide a direct signature of broken mirror and time-reversal symmetry in this topological superfluid. I report on the theory of the anomalous Hall effect of negative ions in the chiral phase of 3He, and explain the origin of the drag and transverse forces on moving ions in 3He-A in terms of combined potential and branch conversion scattering of chiral Bogoliubov quasiparticles off the negative ion and the chiral order parameter.2
2 O. Shevtsov and J. A. Sauls, Electron Bubbles and Weyl Fermions in Chiral Superfluid 3He-A, Phys. Rev. B 94, 064511 (2016).
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