Half quantum vortex in superfluid $^3$He-A phase in parallel plate geometry

We investigate a magnetic susceptibility of vortices in the B phase of multicomponent triplet superfluid $^3$He focusing on a contribution of bound fermionic states localized within vortex cores. Several order parameter configurations relevant to different types of quantized vortices in $^3$He B are considered. It is shown quite generally that an ac magnetic susceptibility has a sharp peak at the frequency corresponding to the energy of interlevel spacing in the spectrum of b...

$^3$He is an example of the system with non-trivial Cooper paring. A few different superfluid phases are known in this system. Recently the new one, the polar phase, have been observed in $^3$He confined in nematically ordered aerogel. A number of various topological defects including half-quantum vortices can exist the polar phase. In this work we present theoretical and numerical studies of linear NMR in the polar phase both in the uniform order-parameter texture and in the...

This is the manuscript version of the Physics ViewPoint article introducing the paper "Observation of half-quantum vortices in topological superfluid $^3$He", by S. Autti et al., which appeared in Physical Review Letters, December 14, 2016.

The formation and dynamics of topological defects of different structure has been of central interest in the study of the 3He superfluids. Compared to superfluid 4He-II, the variability of the important parameters with temperature and pressure is wider and many features are more ideal. This has made experimentally new approaches possible. An example is the formation of quantized vortices and other topological defects in a rapid time-dependent phase transition from the normal ...

This paper studies vortex-lattice phases of rapidly rotating superfluid ^3He based on the Ginzburg-Landau free-energy functional. To identify stable phases in the p-Omega plane (p: pressure; Omega: angular velocity), the functional is minimized with the Landau-level expansion method using up to 3000 Landau levels. This system can sustain various exotic vortices by either (i) shifting vortex cores among different components or (ii) filling in cores with components not used in ...

In quantum electrodynamics, the zero-charge effect originates from the logarithmic dependence of the coupling constant in the action of the electromagnetic field on the ratio of the ultraviolet and infrared energy cutoffs. An analogue of this effect in Weyl superfluid $^3$He-A is the logarithmic divergence of the bending energy of the orbital anisotropy axis at low temperatures, where temperature plays the role of the infrared cutoff and the vector of the orbital anisotropy p...

Motivated by the recent observation and argument on a large half-quantum vortex (HQV) pair connencted by a Kibble wall in superfluid 3He in nematic aerogels, we numerically study to what extent a huge HQV pair can intrinsically occur with no pinning effect due to the aerogel structure in the polar-distorted B (PdB) phase of superfluid 3He. By fully examining the impurity-scattering induced pairing vertex, the emergence of Anderson's Theorem in the p-wave superfluid is verifie...

We discuss the general properties of periodic vortex arrangements in rotating superfluids. The different possible structures are classified according to the symmetry space-groups and the circulation number. We calculate numerically several types of vortex structures in superfluid 3He-A. The calculations are done in the Ginzburg-Landau region, but the method is applicable at all temperatures. A phase diagram of vortices is constructed in the plane formed by the magnetic field ...

Recently new topological phase of superfluid $^3$He has been discovered -- the $\beta$ phase, which is obtained by strong polarization of the nematic polar phase. We consider half-quantum vortices, which are formed in rotating cryostat, and discuss the evolution of the vortex lattice in the process of the transition from the polar phase to the $\beta$-phase via the spin-polarized polar phase.

Vortex flow remains laminar up to large Reynolds numbers (Re~1000) in a cylinder filled with 3He-B. This is inferred from NMR measurements and numerical vortex filament calculations where we study the spin up and spin down responses of the superfluid component, after a sudden change in rotation velocity. In normal fluids and in superfluid 4He these responses are turbulent. In 3He-B the vortex core radius is much larger which reduces both surface pinning and vortex reconnectio...