Many-body effects in coherent transmission through a quantum dot with two degenerate levels

The coherent transmission coefficient for an electron tunneling through a quantum dot is calculated and the effects of electron interactions at the dot are studied. The previous calculations for a dot with a single level are extended to a dot with two degenerate levels. Calculations of the transmission coefficient around a resonance peak are carried out using the noncrossing approximation at temperatures much higher than the level broadening. It is shown that the magnitude of the transmission coefficient decreases in the presence of interactions and the height and the line shape of the resonance peak in the two-level dot are very different from those in the single-level dot. The result is compared with the recent Aharonov-Bohm experiment and the phase coherency in the current through the dot is discussed.