NbSi纳米线量子相位滑移电路：直流超电流阻断、微波测量和热分析
NbSi nanowire quantum-phase-slip circuits: dc supercurrent blockade, microwave measurements and thermal analysis
摘要：
我们提出了一个详细的报告，微波辐射的超窄超导纳米线。在我们的nanofabricated电路含有超导NbSi纳米线，直流阻塞的电流在低温下观察到低于临界电压Vc，量子相位滑移（QPS）在纳米线的存在的一个强有力的指标。我们描述的结果，应用微波这些样品，使用一系列的频率和连续波和脉冲驱动，为了寻找双夏皮罗步骤，这将构成一个明确的演示量子相位滑移。我们没有观察到台阶，我们随后的热分析表明，串联CrO电阻器中的电子温度明显高于衬底温度，从而产生足够的约翰逊噪声来消除台阶。为了了解系统和通知未来的工作，我们已经构建了一个数字模型的动态电路的直流和交流偏置（连续波和脉冲驱动信号）在约翰逊噪声的存在。使用这个模型，我们概述了重要的设计考虑的设备和测量参数，应在任何未来的实验中使用，使双夏皮罗步骤在实验上可访问的温度下观察，从而导致发展的基于量子点的量子电流标准。
英文摘要：
We present a detailed report of microwave irradiation of ultra-narrow superconducting nanowires. In our nanofabricated circuits containing a superconducting NbSi nanowire, a dc blockade of current flow was observed at low temperatures below a critical voltage Vc, a strong indicator of the existence of quantum phase-slip (QPS) in the nanowire. We describe the results of applying microwaves to these samples, using a range of frequencies and both continuous-wave and pulsed drive, in order to search for dual Shapiro steps which would constitute an unambiguous demonstration of quantum phase-slip. We observed no steps, and our subsequent thermal analysis suggests that the electron temperature in the series CrO resistors was significantly elevated above the substrate temperature, resulting in sufficient Johnson noise to wash out the steps. To understand the system and inform future work, we have constructed a numerical model of the dynamics of the circuit for dc and ac bias (both continuous wave and pulsed drive signals) in the presence of Johnson noise. Using this model, we outline important design considerations for device and measurement parameters which should be used in any future experiment to enable the observation of dual Shapiro steps at experimentally accessible temperatures and thus lead to the development of a QPS-based quantum current standard.
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