Identification of Superfluid Phases of 3He in Uniformly Isotropic 98.2% Aerogel

TL;DR

This study uses advanced uniform aerogel materials and NMR experiments to identify superfluid 3He phases, revealing that impurity effects do not destroy long-range order as previously predicted.

Contribution

It provides the first definitive identification of superfluid 3He phases in uniform aerogel, challenging existing theories about impurity effects on orbital order.

Findings

Superfluid 3He in aerogel exhibits isotropic and axial p-wave states.

Impurity effects do not eliminate long-range orbital order.

The Larkin-Imry-Ma effect is not observed in the impure axial state.

Abstract

Superfluid 3He confined to high porosity silica aerogel is the paradigm system for understanding impurity effects in unconventional superconductors. However, a crucial first step has been elusive; exact identification of the microscopic states of the superfluid in the presence of quenched disorder. Using a new class of highly uniform aerogel materials, we report pulsed nuclear magnetic resonance experiments that demonstrate definitively that the two observed superfluid states in aerogel are impure versions of the isotropic and axial p-wave states. The theoretically predicted destruction of long-range orbital order (Larkin-Imry Ma effect) in the impure axial state is not observed.