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

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.