Department of Physics, AlbaNova University Center, Stockholm University, SE-106 91 Stockholm, Sweden.
Phys Rev Lett. 2013 Sep 13;111(11):117002. doi: 10.1103/PhysRevLett.111.117002.
We study the temperature dependence of the critical current modulation I(c)(H) for two types of planar Josephson junctions: a low-Tc Nb/CuNi/Nb and a high-Tc YBa2Cu3O(7-δ) bicrystal grain-boundary junction. At low T both junctions exhibit a conventional behavior, described by the local sine-Gordon equation. However, at elevated T the behavior becomes qualitatively different: the I(c)(H) modulation field ΔH becomes almost T independent and neither ΔH nor the critical field for the penetration of Josephson vortices vanish at Tc. Such an unusual behavior is in good agreement with theoretical predictions for junctions with nonlocal electrodynamics. We extract absolute values of the London penetration depth λ from our data and show that a crossover from local to nonlocal electrodynamics occurs with increasing T when λ(T) becomes larger than the electrode thickness.
我们研究了两种平面约瑟夫森结的临界电流调制 I(c)(H)对温度的依赖性：一种是低温 Tc 的 Nb/CuNi/Nb，另一种是高温 Tc 的 YBa2Cu3O(7-δ)双晶晶界结。在低温下，两个结都表现出一种常规行为，由局域正弦-戈登方程描述。然而，在高温下，行为变得定性上不同：临界电流调制场 ΔH 几乎与 T 无关，并且在 Tc 时，既没有 ΔH 也没有约瑟夫森涡旋穿透的临界场消失。这种异常行为与具有非局域电动力学的结的理论预测非常吻合。我们从数据中提取出伦敦穿透深度 λ 的绝对值，并表明当 λ(T)大于电极厚度时，从局域到非局域电动力学的转变随着温度的升高而发生。
