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. 3), cold atomic gases and superfluid ^3He (ref. 5). 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.

Files

Additional details