NMR Spectroscopy of the Double-Quantum Vortex in Superfluid 3He-A

Abstract

The double-quantum vortex line with continuous (singularity-free) structure is the most common linear defect in rotating 3 He-A. Its well-known experimental signature is a frequency-shifted satellite peak in the NMR spectrum. It arises from the absorption of spin wave excitations, which are localized bound states in the dipole-unlocked soft vortex core. In first approximation, the intensity of the satellite peak is proportional to the number of vortex lines. With increased measuring resolution we have found that the absorption contribution of individual vortex lines is not identical, but displays small variations, which depend on the non-uniform global orbital 1 texture. We attribute the effect to small texture-dependent changes in the 1 distribution in the soft core, which modify the attractive potential of the localized spin waves. This property can be used for studying the global order-parameter texture in the rotating container.