Sound-induced vortex interactions in a zero temperature two-dimensional superfluid

Yauhen Sachkou

Andrew Lucas, Piotr Surówka

We present a systematic derivation of the effective action for interacting vortices in a nonrelativistic two-dimensional superfluid described by the Gross-Pitaevskii equation by integrating out longitudinal fluctuations of the order parameter. There are no logarithmically divergent coefficients in the equations of motion. Our analysis is valid in a dilute limit of vortices where the intervortex spacing is large compared to the core size, and where number fluctuations of atoms in vortex cores are suppressed. We analyze sound-induced corrections to the dynamics of a vortex-antivortex pair and show that there is no instability to annihilation, suggesting that sound-mediated interactions are not strong enough to ruin an inverse energy cascade in two-dimensional zero-temperature superfluid turbulence.

Piotr Surówka

Carlos Wexler

Evgeny Kozik, Boris V. Svistunov

Kelvin waves---helical waves on quantized vortex lines---are the normal modes of vortices in a superfluid. At zero temperature, the only dissipative channel of vortex dynamics is phonon emission. Starting with the hydrodynamic action, we derive the Hamiltonian of vortex-phonon interaction, thereby reducing the problem of the interaction of Kelvin waves with sound to inelastic elementary excitation scattering. On the basis of this formalism, we calculate the rate of sound radiation by superfluid turbulence at zero temperature and estimate the value of short-wavelength cutoff of the turbulence spectrum.

Cheng-Ching Wang, R. A. Duine, Allan H. MacDonald