Cooper-Pair Tunneling in Small Josephson Junction Arrays Under Radio-Frequency Irradiation
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Cooper‑Pair Tunneling in Small Josephson Junction Arrays Under Radio‑Frequency Irradiation Godwill Mbiti Kanyolo1 · Kouichi Takeda1 · Yoshinao Mizugaki1 · Takeo Kato2 · Hiroshi Shimada1 Received: 9 November 2019 / Accepted: 21 May 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The influence of radio-frequency microwaves on the Coulomb blockade characteristics in small Josephson junctions was studied using a one-dimensional array of ten small Al tunnel junctions in the frequency range from 1 to 1000 MHz. Coulomb blockade voltage ( Vth ) is diminished with increasing microwave power ( Vac ), where the Vth–Vac plots for varied frequencies fall on a single curve. We observed and theoretically analyzed a magnetic field dependent renormalization of the applied microwave power, in addition to a magnetic field independent renormalization effect explained using an effective circuit approach of the array. Due to its high sensitivity to microwave power, the array is well-suited for on-chip detection applications in low-temperature environments. Keywords Coulomb blockade · Josephson junction array · Radio-frequency irradiation
1 Introduction Since the pioneering theoretical work by Likharev and co-workers [1–3], small Josephson junctions have been thought of as a dual system to large Josephson junctions—the roles of current and voltage are interchanged. In the case of large Josephson junctions, their effective interaction with oscillating electromagnetic fields has intensively been studied, demonstrating their unique suitability for microwave-based * Godwill Mbiti Kanyolo [email protected] Hiroshi Shimada [email protected] 1
Department of Engineering Science, The University of Electro-Communications, 1‑5‑1 Chofugaoka, Chofu, Tokyo 182‑8585, Japan
2
Institute for Solid State Physics, The University of Tokyo, 5‑1‑5 Kashiwanoha, Kashiwa 277‑8581, Japan
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Vol.:(0123456789)
Journal of Low Temperature Physics
applications such as the metrological standard for the Volt [in terms of voltage (V) Shapiro steps] and other microwave-based devices [4]. Thus, the dual system holds enormous promise for complementary applications such as a metrological standard for the Ampere in terms of the current (I) Shapiro steps [1, 2]. However, due to their mesoscopic size, microwave-based studies with oscillating electromagnetic fields face daunting experimental and theoretical challenges. In particular, small junctions are prone to quantum and thermal fluctuations; thus, a well-known (fluctuation-dissipation) theorem applies [5, 6]. Due to their fluctuative nature, the characteristics of small junctions generally cannot be analyzed separately from their dissipative environment [7, 8]. Consequently, special considerations and techniques are required to observe such dual characteristics as the Coulomb blockade and Bloch oscillations in a single small junction [9, 10]. For a one-dimensional (1D) array of small Josephson junctions, however, Coulomb blockade is easily observed when the juncti
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