High frequency response of open quantum dots

Full text: We investigate the response of the transport through open quantum dots to millimeterwave radiation (up to 55 GHz). In the low-field region ( < 1T) the behavior of the electrons in the dot can be treated in a semi-classical picture in terms of the trajectories of the electrons moving through the dot. For example, an electron following a quasi-triangular trajectory, after two bounces in the dot, can exit the dot at its entrance causing a backscattering peak in the resistance at a certain magnetic field. The dot systems are defined using finger gate structures on top of a 2DES in a AlGaAs/GaAs heterostructure. The 2DES has a carrier density of 2.5 1011cm-2 and a mobility of 1.2 106cm2/Vs. By applying a sufficiently negative voltage to the gates the 2DES is split into two regions connected only by a dot-like region (about 350 nm diameter) between them. The DC data exhibit backscattering peaks at fields of a few tenth of a Tesla. Shubnikovde- Haas (SdH) oscillations appear above 0.5 T. While the SdH oscillations show the usual temperature dependence, the backscattering peaks are temperature independent up to 2.5 K. The backscattering peak shows a reduction of 10 percent due to the millimeterwave irradiation. However, due to the temperature independence of this peak, this reduction cannot simply be attributed to electron heating. This conclusion is supported by the observation of a strong frequency dependence of the reduction of the peak height. (author)