Directed electron transport through a ballistic quantum dot under microwave radiation

Rectification of microwave radiation by asymmetric ballistic dot is studied at different frequencies (1-40 GHz), temperatures, and magnetic fields. Dramatic reduction of the rectification is found in magnetic fields at which the cyclotron radius of electron orbits at the Fermi level is less than the size of the dot. With respect to the magnetic field, both symmetric and antisymmetric contributions to the rectification are presented. The symmetric part changes significantly with microwave frequency omega at omegatau_{f}>/=1, where tau_{f} is the time of the ballistic electron flight across the dot. The results lead consistently towards the ballistic origin of the effect, and can be explained by strongly nonlocal electron response to the microwave electric field, which affects both speed and direction of the electron motion inside the dot.