Analog of Anderson theorem for the polar phase of liquid 3He in nematic aerogel

TL;DR

This paper demonstrates that in superfluid 3He with certain impurity structures, the transition temperature to the polar phase remains unchanged from the pure case, unless magnetic impurities are present, which lower it, paralleling superconductivity behavior.

Contribution

It extends the Anderson theorem to the polar phase of superfluid 3He with non-magnetic impurities, showing conditions under which the transition temperature remains unaffected.

Findings

Non-magnetic, straight, parallel impurities do not change the transition temperature.

Magnetic impurities reduce the transition temperature.

Results align with recent experimental observations.

Abstract

It is shown that if impurities in superfluid 3He have form of infinitely long non-magnetic strands, which are straight, parallel to each other and reflect quasi-particles specularly, the temperature of transition of liquid 3He from the normal into the polar phase coincides with that for the bulk liquid without impurities. Magnetic scattering lowers transition temperature for the polar phase in analogy with the conventional superconductors. These results are discussed in connection with the recent experimental findings.