Abstract
Using a novel transfer matrix method, photon-assisted quantum transport through a quantum point contact (QPC) has been studied theoretically. Although the previous WKB theory predicts a ministep structure in the conductance of an irradiated QPC, negative experimental evidence has been reported so far. Our numerical results for a two-dimensional QPC model with realistic parameters suggest that (i) clear ministeps can be expected if the radiation field is several times stronger than that in experiments, (ii) in contrast to the WKB prediction, only ministeps in the emission side will be observed, and (iii) a wavefunction modulation by a static potential plays an important role in photon-assisted quantum transport, which has not been properly evaluated in the previous theory. We also insist that a simple scenario based on the Tien-Gordon picture does not describe correctly the ministep structure.
