Electromagnetic response of charged bosons coupled to a Chern-Simons gauge field: A path-integral approach

We analyze the electromagnetic response of a system of charged bosons coupled to a Chern-Simons (CS) gauge field. Path-integral techniques are used to obtain an effective action for the particle density of the system dressed with quantum fluctuations of the CS gauge field. From the action thus obtained we compute the U(1) current of the theory for an arbitrary electromagnetic external field. For the particular case of a homogeneous external magnetic field, we show, neglecting the back reaction of density-current to electromagnetic fields, the quantization of the transverse conductivity, even in the presence of an arbitrary impurity distribution. The relevance of edge states in this context is analyzed. The propagator of density fluctuations is computed, and an effective action for the matter density in the presence of a vortex excitation is suggested.