SUPERFLUIDITY IN THE 2-DIMENSIONAL GAUGE-FIELD MODEL - A RENORMALIZATION-GROUP ANALYSIS

We study an effective action of bosons interacting with a gauge field, which is derived from the t-J model in the slave-boson approach. We u se a renormalization-group (RG) scheme to calculate the temperature T( BE), below which the bosons start to condense in a superfluid state. O ne expects that a strongly fluctuating gauge field tends to destroy th is superfluid state. Our numerical calculations indeed show that the p resence of a gauge field suppresses the onset of superfluidity. This s uppression is partly due to quantum fluctuations, and partly due to th ermal excitations of the gauge field. An analytical calculation of the flow in the classical regime T(l) much greater than 1 shows that our perturbative RG scheme provides an expansion of the suppression of T(B E) in powers of q00(2)/u0, where q00(2) is the coupling constant of th e gauge field, and u0 is the short-range repulsion between the bosons. The RG scheme breaks down if q00(2)/u0 greater than or similar to 1, in which case one gets into the strong-coupling limit. Thus unfortunat ely the RG scheme is not reliable for the strong-coupling problem, whi ch is appropriate for the t-J model with t/J approximately 1.