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arXiv 0708.0230cond-mat.supr-concond-mat.mes-hall
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π结超导阵列中的自发电流成像

Imaging spontaneous currents in superconducting arrays of pi-junctions

Sergey M. Frolov, Micah J. A. Stoutimore, Trevis A. Crane, Dale J. Van Harlingen, Vladimir A. Oboznov, Valery V. Ryazanov, Adele Ruosi, Carmine Granata, Maurizio Russo

摘要:

由薄隧穿势垒分隔的超导体表现出约瑟夫森效应,其允许在零电压下的电荷传输,通常在最低能量状态下的超导体之间没有相移。最近,三十年前理论提出的具有π的基态相移的约瑟夫森结已经被证实。在超导回路中,π结在零磁场中引起持续电流的自发循环,类似于自旋1/2系统。在这里,我们使用扫描SQUID显微镜图像的自发零场电流的温度控制的π结的超导网络与弱铁磁势垒。我们发现,在0 π的转变温度Tpi = 3 K的结自发超导电流的发病。我们的图像中的电流在非均匀挫折阵列组成的细胞与偶数和奇数的π结。这样的阵列是有吸引力的模型系统,用于研究2D XY模型的奇异相位和实现可扩展的绝热量子计算机。

英文摘要:

Superconductors separated by a thin tunneling barrier exhibit the Josephson effect that allows charge transport at zero voltage, typically with no phase shift between the superconductors in the lowest energy state. Recently, Josephson junctions with ground state phase shifts of pi proposed by theory three decades ago have been demonstrated. In superconducting loops, pi-junctions cause spontaneous circulation of persistent currents in zero magnetic field, analogous to spin-1/2 systems. Here we image the spontaneous zero-field currents in superconducting networks of temperature-controlled pi-junctions with weakly ferromagnetic barriers using a scanning SQUID microscope. We find an onset of spontaneous supercurrents at the 0-pi transition temperature of the junctions Tpi = 3 K. We image the currents in non-uniformly frustrated arrays consisting of cells with even and odd numbers of pi-junctions. Such arrays are attractive model systems for studying the exotic phases of the 2D XY-model and achieving scalable adiabatic quantum computers.

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