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arXiv 1003.2785cond-mat.mes-hallquant-ph
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强射频场中的Andreev干涉仪

Andreev Interferometers in a Strong Radio Frequency Field

C. Checkley, A. Iagallo, R. Shaikhaidarov, J. T. Nicholls, V. T. Petrashov

摘要:

实验研究了1-40 GHz辐射对正常(N)介观导体耦合到超导(S)环(Andreev干涉仪)电阻的影响。在低RF振幅,我们观察到通常的h/2 e超导相周期电阻振荡作为施加的磁通量的函数。我们发现,振荡获得一个π位移与RF幅度的增加,并与此结果相一致的电阻在固定的相位是一个振荡的RF幅度的函数。定性解释的结果作为两个过程的结果。第一种是通过RF场调制N/S界面之间的相位差,电阻随相位变化。第二个过程是由RF场引起的电子温度的变化。从数据中估计Andreev干涉仪的响应时间为<40 ps。然而,有一些实验特征仍然无法解释;这些包括电阻在不同相位的行为作为RF频率和振幅的函数的巨大差异,以及存在“透明窗口”,其中加热效应足够弱以允许π位移。需要一个描述射频辐射对Andreev干涉仪影响的微观理论。

英文摘要:

We experimentally study the influence of 1-40 GHz radiation on the resistance of normal (N) mesoscopic conductors coupled to superconducting (S) loops (Andreev interferometers). At low RF amplitudes we observe the usual h/2e superconducting-phase-periodic resistance oscillations as a function of applied magnetic flux. We find that the oscillations acquire a pi-shift with increasing RF amplitude, and consistent with this result the resistance at fixed phase is an oscillating function of the RF amplitude. The results are explained qualitatively as a consequence of two processes. The first is the modulation of the phase difference between the N/S interfaces by the RF field, with the resistance adiabatically following the phase. The second process is the change in the electron temperature caused by the RF field. From the data the response time of the Andreev interferometer is estimated to be <40ps. However there are a number of experimental features which remain unexplained; these include the drastic difference in the behaviour of the resistance at different phases as a function of RF frequency and amplitude, and the existence of a "window of transparency" where heating effects are weak enough to allow for the pi-shift. A microscopic theory describing the influence of RF radiation on Andreev interferometers is required.

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