Composition of quantum ratchets with chaotic dots

• We present a proposal for a new type of quantum ratchets in application of weak-localization (WL) effect in mesoscopic chaotic dots. Coherent electrons transport through the dots under an applied ac voltage and a synchronized pulsating magnetic field. In the first half cycle of the voltage alternation with no magnetic field, the WL effect reduces the electron transmission on average, while the applied magnetic field breaks the time-reversal symmetry in the latter half cycle, suppressing the WL effect. As a result, nonvanishing amount of net electric current in one direction can be measured. We exactly calculate the net electric current which is found accessible in experiments. It is also suggested that the observation of this rectified current is a good quantitative measure of the WL effect in mesoscopic chaotic dots, in contrast with the WL lineshape measurement.

Nyckelord

quantum ratchet

quantum dot

weak localization

chaotic dot

mesoscopic physics

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