Analog of the Anderson Theorem for the Polar Phase of Liquid 3He in a Nematic Aerogel
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The effect of an aerogel with parallel fibers on the temperatures of 3He transition to superfluid phases differing in the lz projections of the orbital angular momentum on the directions of the fibers is considered. It is shown that at the specular reflection of Fermi excitations of liquid 3He from the fibers, the temperature of transition to the polar phase corresponding to lZ = 0 remains the same as the temperature of transition to any phase with orbital angular momentum l = 1 in the absence of the aerogel. The temperature of transition into phases with lz = ±1 turns out to be lower, and there appears to be a finite temperature interval in which only the polar phase is stable. This interval has been determined. The effect of the magnetic (exchange) scattering of Fermi excitations at adsorbed 3He atoms on the temperature of transition of 3He to the superfluid state has been estimated.
I am grateful to V.V. Dmitriev for fruitful discussions and constructive critical remarks.
This study was performed within the Program of the Presidium of the Russian Academy of Sciences no. 1.4 “Topical Problems in Low-Temperature Physics.”