Phase diagram of superfluid 3He in “nematically ordered” aerogel

Abstract

Results of experiments with liquid 3 He immersed in a new type of aerogel are described. This aerogel consists of Al 2 O 3 ⋅ H 2 O strands which are nearly parallel to each other, so we call it as a "nematically ordered" aerogel. At all used pressures a superfluid transition was observed and a superfluid phase diagram was measured. Pos sible structures of the observed superfluid phases are discussed.

Anisotropic Phases of SuperfluidHe3in Compressed Aerogel

“…They are just two of many p-wave states each distinguished by unique broken symmetries and these are the only stable states in pure 3 He in low magnetic field [1]. However, new phases in this manifold have been reported for superfluid confined within an anisotropic external framework; in one case chiral states within positively strained 98% porous, silica aerogel [2] and in another, equal spin pairing states within nematically oriented alumina hydrate aerogels [3].…”

“…It has been shown that the relative stabilities of various superfluid states of 3 He can be influenced by anisotropy in a silica aerogel framework. We prepared a suite of aerogel samples compressed up to 30% for which we performed pulsed NMR on 3 He imbibed within the aerogel.…”

“…They are just two of many p-wave states each distinguished by unique broken symmetries and these are the only stable states in pure 3 He in low magnetic field [1]. However, new phases in this manifold have been reported for superfluid confined within an anisotropic external framework; in one case chiral states within positively strained 98% porous, silica aerogel [2] and in another, equal spin pairing states within nematically oriented alumina hydrate aerogels [3]. Additionally, for a negatively strained aerogel, obtained by compression, we found that the relative thermodynamic stability between the A and B-phases can be reversed resulting in an unusual tricritical point between A, B, and normal phases with a critical magnetic field of H c ≈ 100 mT [4].…”

“…The A and B-phases of superfluid 3 He are unconventional Cooper paired states with orbital angular momentum L = 1. They are just two of many p-wave states each distinguished by unique broken symmetries and these are the only stable states in pure 3 He in low magnetic field [1].…”

“…We prepared a suite of aerogel samples compressed up to 30% for which we performed pulsed NMR on 3 He imbibed within the aerogel. We identified A and B-phases and determined their magnetic field-temperature phase diagrams as a function of strain.…”