Hard domain walls in superfluid 3He-B
  We study theoretically planar interfaces between two domains of superfluid 3He-B. The structure of the B-B walls is determined on the scale of the superfluid condensation energy, and thus the domain walls have thickness on the order of the Ginzburg-Landau coherence length. We study the stability and decay schemes of five inequivalent structures of such domain walls using one-dimensional Ginzburg-Landau simulation. We find that only one of the structures is stable against small perturbations. We also argue that B-B interfaces could result from adiabatic A to B transition and study textures at B-B interfaces. The B-B interface has a strong orienting effect on spin-orbit rotation producing textures similar as caused by external walls. We study the B-B interface in a parallel-plate geometry and find that the conservation of spin current sets an essential condition on the structure. The stable B-B interface gives rise to half-quantum circulation. 
Matti Silveri, Tero Turunen, and Erkki Thuneberg (University of Oulu)
cond-mat.supr-con