Bragg reflection from equidistant planes of vortex sheets in rotating 3He-A
Parts U., Koivuniemi J. H., Krusius M., Ruutu V. M. H., Thuneberg E. V., Volovik G. E.
Recently a new state of rotating superfluid 3He-A, which consists of equidistant planes of vortex sheets, was discovered. Its cw NMR absorption spectrum includes a small satellite peak which has the largest relative frequency shift ever observed in 3He-A. This peak is attributed to the excitation of a stationary spin wave mode which is localized in the gaps between the vortex sheets. This mode corresponds to the first Bragg reflection from a one-dimensional periodic potential. The frequency shift provides a measurement of the distance between vortex sheets. This distance agrees with the prediction of Landau and Lifshitz in 1955.