New chiral phases of superfluid 3He stabilized by anisotropic silica aerogel

Abstract

A rich variety of Fermi systems condense by forming bound pairs, including high-temperature and heavy-fermion superconductors, Sr 2RuO 4 (ref.), cold atomic gases and superfluid 3He (ref. ). Some of these form exotic quantum states with non-zero orbital angular momentum. We have discovered, in the case of 3He, that anisotropic disorder, engineered from highly porous silica aerogel, stabilizes a chiral superfluid state that otherwise would not exist. Furthermore, we find that the chiral axis of this state can be uniquely oriented with the application of a magnetic field perpendicular to the aerogel anisotropy axis. At sufficiently low temperature we observe a sharp transition from a uniformly oriented chiral state to a disordered structure consistent with locally ordered domains, contrary to expectations for a superfluid glass phase. © 2012 Macmillan Publishers Limited. All rights reserved.