On Superfluidity and Suppressed Light Scattering in BECs

TL;DR

This paper demonstrates that light scattering suppression in Bose-Einstein Condensates (BECs) is directly linked to superfluidity, rooted in the entangled ground state correlations that prevent low-energy excitations, confirming superfluidity as the cause.

Contribution

It establishes the equivalence between light scattering suppression and superfluidity in BECs through the principle of superfluidity and ground state entanglement.

Findings

Suppressed light scattering is due to superfluidity.

Ground state entanglement prevents low-energy excitations.

Excitations are Bogolyubov quasiparticles, not free bosons.

Abstract

We show that the suppression of light scattering off a Bose Einstein Condensate is equivalent to the Landau argument for superfluidity and thus is a consequence of the {\it Principle of Superfluidity}. The superfluid ground state of a BEC contains nonseparable, nontrivial correlations between the bosons that make up the system, i. e., it is entangled. The correlations in the ground state entangle the bosons into a coherent state for the lowest energy state. The entanglement is so extreme that the bosons that make up the system cannot be excited at long wavenumbers. Their existence at low energies is impossible. Only quantum sound can be excited, i.e. the excitations are Bogolyubov quasiparticles which do not resemble free bosons whatsoever at low energies. This means that the system is superfluid by the Landau argument and the superfluidity is ultimately the reason for suppressed scattering at low wavelengths.