We study the microwave induced ratchet transport of two-dimensional electrons
on an oriented semidisk Galton board. The magnetic field symmetries of ratchet
transport are analyzed in presence of electron-electron interactions. Our
results show that a magnetic field asymmetric ratchet current can appear due to
two contributions, a Hall drift of the rectified current that depends only
weakly on electron-electron interactions and a breaking of the time reversal
symmetry due to the combined effects of interactions and magnetic field. In the
latter case, the asymmetry between positive and negative magnetic fields
vanishes in the weak interaction limit. We also discuss the recent experimental
results on ratchet transport in asymmetric nanostructures.Comment: 5 pages, 4 figure
