Surface Majorana Cone of the Superfluid $^3$He B Phase

TL;DR

This paper reports experimental evidence of Majorana fermion surface states in superfluid $^3$He B phase through acoustic impedance measurements, confirming the theoretical Majorana cone dispersion relation.

Contribution

It provides the first experimental confirmation of Majorana surface states in superfluid $^3$He B phase by linking impedance measurements to the Majorana cone.

Findings

Growth of impedance peak on higher specularity wall

Variation of impedance linked to Majorana cone formation

Confirmation of Majorana fermion surface states

Abstract

The superfluid $^3$He B phase, one of the oldest unconventional fermionic condensates experimentally realized, is recently predicted to support Majorana fermion surface states. Majorana fermion, which is characterized by the equivalence of particle and antiparticle, has a linear dispersion relation referred to as the Majorana cone. We measured the transverse acoustic impedance $Z$ of the superfluid$^3$He B phase changing its boundary condition and found a growth of peak in $Z$ on a higher specularity wall. Our theoretical analysis indicates that the variation of $Z$ is induced by the formation of the cone-like dispersion relation and thus confirms the important feature of the Majorana fermion in the specular limit.