Tangential instability of the superfluid–normal interface in a phase-separated 3He– 4He liquid mixture

Abstract

We study small oscillations of the interface between 3He-dilute superfluid and 3He-concentrated normal phases of a liquid 3He– 4He mixture. A tangential instability specific only for the superfluid–normal interface is found. The interface becomes unstable provided the superfluid component flows in the direction tangential to the interface at a velocity exceeding the critical one of about 6.3 cm/s. The wavelength of the ripple structure equals the capillary constant of about 1.3 mm. The effect of the boundary conditions and phase-separation kinetics at the interface upon the oscillation spectrum is discussed.