Surface Majorana cone of the topological superfluid 3He B phase

Author-Highlights
• Surface states of superfluid 3He were revealed by transverse acoustic impedance.
• Surface density of states sensitively depends on the boundary condition.
• Surface Majorana cone was confirmed experimentally on a specular wall.
• Superfluid 3He was shown to be truly a topological superfluid.
• Majorana fermions are realized as quasiparticles in condensed matter.

Topological superfluids and superconductors have been theoretically proposed, and it is now necessary to experimentally confirm their existence. Superfluid 3He should be the ideal test subject for topological theories because its bulk state is established to be that of a spin-triplet p-wave superfluid. Surface Andreev bound states of superfluid 3He were investigated by transverse acoustic impedance measurements and their linear dispersion was confirmed on a highly specular wall. The superfluid 3He B phase was found to be a topological superfluid showing bulk–edge correspondence and a surface Majorana cone was confirmed on the surface. Possible manifestations of the Majorana nature of the surface states are discussed.