Half quantum vortex in superfluid (3)He-A phase in parallel-plate geometry

The half quantum vortex (HQV) in condensates has been studied, since it was predicted by Volovik and Mineev, and independently by Cross and Brinkman in superfluid (3)He-A phase. However, no experimental evidence for its existence has been reported until recently. Motivated by a recent experimental report by Yamashita et al. (AIP Conf. Proc., 850 (2006) 185; private communication) we study the HQVs in superfluid (3)He confined between two parallel plates with a gap D similar to 10 mu m in the presence of a magnetic field H similar to 26mT perpendicular to the parallel plates. We find that the bound HQVs are more stable than the singular vortices and free pairs of HQVs, when the rotation perpendicular to the parallel plates is below the critical speed, Omega(c) = 2 similar to 12 rad/s, if the magentic healing length, xi(H) is about 2-5 mu m. The bound pair of HQVs accompanies the tilting of (d) over cap -vector out of the plane, which leads to an additional absorption in NMR spectra. Our study appears to describe the temperature and rotation dependence of the observed satellite NMR signal, which supports the existence of the HQVs in (3)He. Copyright (c) EPLA, 2007.