Masahiro Wasai

Surface Majorana cone of the superfluid 3He B phase

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.

Transverse Acoustic Impedance of Superfluid 3 He B Phase in Weak Magnetic Fields

Transverse acoustic impedance was measured in the superfluid 3He B phase in magnetic fields to investigate the magnetic response of the surface bound states on a diffusive wall. The peak structure of the impedance in the temperature dependence disappeared in 50 mT and this disappearance is possibly a reflection of the gap distortion in the field.

Transverse acoustic impedance of normal liquid 3He with 4He coating

We measured the transverse acoustic impedance of the normal liquid 3He at 16 MHz and 10 bar with and without 4He layers plated on a wall in the temperature range of 500 to 3 mK. The real component of the impedance gradually increased with cooling in the high-temperature hydrodynamic region and saturated in the low-temperature collisionless region. In the crossover region around 20 mK, the real component had a steep increase and the imaginary component was minimum. Overall change in the temperature dependence became smaller by 4He coating and we can obtain the specularity parameter S of the wall by fitting the temperature dependence of the experimental impedance to the theory.