Persistent Precessing Texture-Trapped Domains in Low Temperature Superfluid ³He

Abstract

It has recently been discovered that at temperatures below about 0.2T _C in superfluid ³ He-B, pulsed NMR excitation can generate a new coherently precessing spin state which can have a lifetime of tens of seconds. The free induction decay signal from this state has been called the persistent induction signal (PIS). The earlier observations of the PIS have found it to be highly irreproducible indicating a strong connection with the magnetic texture. Here we describe measurements of the PIS within an experimental cell which was designed to fix the textural configuration of the superfluid. The resulting PIS signals are now far more reproducible allowing a more systematic study of the behaviour which we present here. Furthermore in the latest cell the decay of this signal has been observed to last for up to 4 minutes at the lowest temperatures. While the precessing state is readily accessible to observation, at these temperatures it is a very delicate object and we can immediately see the influence of background radiation on the time evolution of the decay.