Aharonov-Bohm interferometry with a tunnel-coupled wire
Aharonov-Bohm interferometry with a tunnel-coupled wire
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DOI：
10.1088/1367-2630/16/8/083015
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发表时间：
2014-08-07
影响因子：
3.3
通讯作者：
Tarucha, S.
中科院分区：
文献类型：
--
作者：
Aharony, A.;Takada, S.;Tarucha, S.
最近的实验(Yamamoto等人2012自然纳米技术7 247)使用了电子通过Aharonov-Bohm(AB)干涉仪和两个耦合通道(在干涉仪两端)的传输来演示可操纵的飞行量子比特。结果包括两个输出电流的同相和反相(AB)振荡作为磁通量的函数，分别针对强和弱通道间耦合。在此，我们给出了一个三端干涉仪的新实验结果，该干涉仪在两根出线之间存在隧道耦合。我们表明，在一定的限制下，该系统是“双缝”实验的一种更简单的实现。我们还提出了一个简单的紧束缚理论模型，它模拟了实验装置。对于弱通道间耦合，从器件反射的电流中的AB振荡非常小，因此两个输出电流中的振荡必须相互抵消，从而产生反相行为，与耦合区域的长度无关。从技术上讲，两条耦合导线内的紧束缚方程对每个电子能量有四个解。在“反相区”，所有这些解都是波浪状的，随着导线的距离而振荡。当导线之间的耦合增强时，其中两个解就会消失，它们的幅度会随着电子在导线中的运动而衰减。在这种情况下，剩下的两个“运行”波的幅度是成比例的，其比率实际上是与通量无关的。结果，这两个输出电流成正比，从而产生“同相”行为。对于更大的耦合，所有的解都是消失的，并且输出电流变得非常小。
Recent experiments (Yamamoto et al 2012 Nature Nanotechnology 7 247) used the transport of electrons through an Aharonov-Bohm (AB) interferometer and two coupled channels (at both ends of the interferometer) to demonstrate a manipulable flying qubit. Results included in-phase and anti-phase (AB) oscillations of the two outgoing currents as a function of the magnetic flux, for strong and weak inter-channel coupling, respectively. Here we present new experimental results for a three terminal interferometer, with a tunnel coupling between the two outgoing wires. We show that in some limits, this system is an even simpler realization of the 'two-slit' experiment. We also present a simple tight-binding theoretical model which imitates the experimental setup. For weak inter-channel coupling, the AB oscillations in the current which is reflected from the device are very small, and therefore the oscillations in the two outgoing currents must cancel each other, yielding the anti-phase behavior, independent of the length of the coupling regime. Technically, the tight binding equations within the two coupled wires have four solutions for each electronic energy. In the 'anti-phase' region all of these solutions are wave-like, oscillating with the distance along the wires. As the coupling between the wires increases, two of these solutions become evanescent, and their amplitudes decay as the electron moves in the wires. In this regime, the amplitudes of the two remaining 'running' waves are proportional to each other, with a ratio which is practically flux-independent. As a result, the two outgoing currents are proportional to each other, yielding the 'in phase' behavior. For larger coupling all the solutions are evanescent, and the outgoing currents become very small.