Condensed Matter Seminars

In high magnetic field and at low temperatures, liquid He-3 condenses into a unique superfluid phase (A1) in which the condensate is spin-polarized. Owing to the broken relative symmetry in gauge and spin spaces, A1 phase hydrodynamics has unusual properties. To demonstrate the unusual hydrodynamics, two experiments on (1) magnetic fountain effect and (2) spin-entropy wave (SEW) propagation will be discussed. (1)Owing to the ability to respond to gradients in pressure, temperature as well as magnetic field, A1 phase should develop a steady pressure gradient across two chambers when a steady magnetic field gradient is applied across a superleak connecting the two chambers. Such magnetic fountain effect has been observed but with shorter relaxation time than expected. The observed relaxation is likely related to the important but not yet well-understood spin relaxation phenomenon occurring at the wall boundaries. (2)The superfluid-normal fluid counter-flow propagating mode in A1 phase is accompanied by oscillations in both entropy and spin densities. The large “spin stiffness” makes the velocity of this SEW is much greater that it would be for “entropy stiffness” alone. The measured SEW velocity gives the superfluid density directly. Anisotropy in the superfluid density may be studied with SEW. The liquid-crystal-like property of anisotropy “texture” may be probed and its kinetic anisotropy “texture phase transition” has been observed.