Polarization Effects in Superfluid $^4$He

TL;DR

This paper develops a theory of thermoelectric effects in superfluid helium-4, predicting tiny electric signals from sound waves and polarization phenomena related to second sound, with results aligning with experimental data.

Contribution

It introduces a theoretical framework for polarization and thermoelectric effects in superfluid helium-4, including estimations of atomic dipole moments and electric signals generated by sound waves.

Findings

Electric signals from sound waves are extremely small.

Second sound induces polarization proportional to temperature gradients.

Predicted polarization ratios are consistent with experimental observations.

Abstract

A theory of thermoelectric phenomena in superfluid $^4He$ is developed. It is found an estimation of the dipole moment of helium atom arising due to electron shell deformation caused by pushing forces from the side of its surrounding atoms. The corresponding electric signal generated in a liquid consisting of electrically neutral atoms by the ordinary sound waves is found extremely small. The second sound waves in superfluid $^4He$ generate the polarization of liquid induced by the relative accelerated motion of the superfluid and the normal component. The derived ratio of the amplitudes of temperature and electric polarization potential was proved to be practically temperature independent. Its magnitude is in reasonable correspondence with the experimental observations. The polarity of electric signal is determined by the sign of temperature gradient in accordance with the measurements. The problem of the roton excitations dipole moment is also discussed.