EIT-like phenomenon with two atomic ensembles in a cavity

We study the spectra of collective low excitations of two atomic ensembles coupled indirectly through a single-mode cavity field. When the left ensemble is driven with an external optical field, its corresponding response spectrum to the incident optical light shows an electromagnetically induced transparency- (EIT-) like phenomenon when the layers are arranged in the sequence of node-antinode but not in the sequence of antinode-node. In the case of antinode-antinode sequence, the response spectrum shows an EIT-like phenomenon with two transparent windows. We also investigate the fluctuation spectra of the atomic collective excitation modes, which show similar EIT-like phenomena.