Composite-field Goldstone states and Higgs mechanism in dilute Bose gases

We show that a composite-field (diatom) Goldstone state is expected in a dilute Bose gas for temperatures between the Bose gas critical temperature where the atom Bose-Einstein condensate appears and the temperature where superfluidity sets in. The presence of superfluidity is tied to the existence of a U(1) charge-two diatom condensate in the system. By promoting the global U(1) symmetry of the theory to a gauge symmetry, we find that the mass of the gauge particle generated through the Anderson-Higgs mechanism is related to the superfluid density via the Meissner effect, and the superfluid density is related to the square of the anomalous density in the Bose system.

Figure 1

The LOAF phase diagram.

Figure 2

(top) Comparison of the atom BEC condensate density ${\rho }_0$ and the superfluid density ${\rho }_s$ for ${\rho }^{1/3}{a}_0=0.4$. (bottom) Comparison of $A^2$ and ${\rho }_s$. Here $A_0\equiv A(T=0)$.