國立中興大學物理學系

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2017-11-23

演講 『Dr. Kimitoshi Kono:An evidence for Majorana fermions on the surface of superfluid 3He-B phase』

Superfluid 3He is a BCS type p-wave superfluid. Ions moving in the superfluid 3He scatter off thermally excited quasiparticles and the transport properties are determined by the quasiparticle scattering. The 3He-A phase is characterized by the psuedovector field of Cooper pair orbital-angular-momentum, which aligns perpendicularly to the surface. This chiral symmetry breaking results in a skew scattering of quasiparticles from the moving ions. And hence, the anomalous Hall effect (AHE) of ion current occurs[1]. Our observation of this AHE[2] is quantitatively explained by the recent theory[3].

In the vicinity of the surface of the 3He-B phase, on the other hand, low-energy quasiparticle subgap surface bound states form, which have been known as the Andreev surface bound states (ASBS).  Chung and Zhang[4] unvailed that the ASBS are Majorana fermions.  We observed an 
excess scattering from the ASBS in the surface ion mobility. Surprisingly, it does show no depth dependence, however[5].  The recent theory of Tsutsumi showed that the observed properties of ion mobility accord with the concept of Majorana fermions[6].  We now obtain a clear evidence for the surface Majorana fermions in the superfluid 3He-B phase.

References:
[1] R. H. Salmelin, M. M. Salomaa, and V. P. Mineev, Phys. Rev. Lett. 63, 868 (1989).
[2] H. Ikegami, Y. Tsutsumi, and K. Kono, Science 341, 59 (2013).
[3] O. Shevtsov and J. A. Sauls, Phys. Rev. B 94, 064511 (2016).
[4] S. B. Chung and S.-C. Zhang, Phys. Rev. Lett. 103, 235301 (2009).
[5] H. Ikegami, S. B. Chung, and K. Kono, J. Phys. Soc. Jpn. 82, 124607 (2013).
[6] Y. Tsutsumi, Phys. Rev. Lett. 118, 145301 (2017).