2014/09/12 by YeJe Park, Suk Bum Chung, Joseph Maciejko · 1 citation
Physics and Astronomy · #cond-mat.supr-con #cond-mat.other
paper · pdf · doi:10.1103/physrevb.91.054507
published as Phys. Rev. B 91, 054507 (2015)
arxiv created 2014/09/12 · arxiv updated 2015/03/04
The theoretical study of topological superfluids and superconductors has so far been carried out largely as a translation of the theory of noninteracting topological insulators into the superfluid language, whereby one replaces electrons by Bogoliubov quasiparticles and single-particle band Hamiltonians by Bogoliubov-de Gennes Hamiltonians. Band insulators and superfluids are, however, fundamentally different: while the former exist in the absence of inter-particle interactions, the latter are broken symmetry states that owe their very existence to such interactions. In particular, unlike the static energy gap of a band insulator, the gap in a superfluid is due to a dynamical order parameter that is subject to both thermal and quantum fluctuations. In this work, we explore the consequences of bulk quantum fluctuations of the order parameter in the B phase of superfluid 3He on the topologically protected Majorana surface states. Neglecting the high-energy amplitude modes, we find that one of the three spin-orbit Goldstone modes in 3He-B couples to the surface Majorana fermions. This coupling in turn induces an effective short-range two-body interaction between the Majorana fermions, with coupling constant inversely proportional to the strength of the nuclear dipole-dipole interaction in bulk 3He. A mean-field theory estimate of the value of this coupling suggests that the surface Majorana fermions in 3He-B are in the vicinity of a quantum phase transition to a gapped time-reversal symmetry breaking phase.