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arXiv 2011.02997cond-mat.supr-con
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非均匀超导岛链中的超导相变

Superconducting phase transition in inhomogeneous chains of superconducting islands

Eduard Ilin, Irina Burkova, Xiangyu Song, Michael Pak, Dmitri S. Golubev, Alexey Bezryadin

摘要:

我们研究了一维超导岛链,特别强调的制度,其中每隔一个岛切换到正常状态,从而形成一个超导体-绝缘体-正常金属(S-I-N)重复模式。如自Giaever隧穿实验以来已知的,当温度降低并且超导体的能隙增长大于热能时,超导体和正常金属之间的隧穿电荷传输变为指数抑制,并且零偏置电阻发散。在这里,我们表明,这种物理现象强烈影响输运性质的非均匀超导体的弱耦合岛屿的波动值的临界温度。我们观察到一个非单调的温度和磁场上的链电阻的依赖关系,在一些,但不是所有的岛屿超导的温度下有一个明显的电阻峰值。我们解释了这种现象的不均匀性的链,其中相邻的超导岛有略有不同的临界温度。我们认为,Giaever的电阻发散也可以发生在零温度极限。如果调节磁场,使得其抑制具有较弱临界场的岛中的超导性,而具有较强能隙的岛保持超导性,则可以发生这种量子跃迁。在这样一个领域,系统作为一个链的S-I-N结。

英文摘要:

We study one dimensional chains of superconducting islands with a particular emphasis on the regime in which every second island is switched into its normal state, thus forming a superconductor-insulator-normal metal (S-I-N) repetition pattern. As is known since Giaever tunneling experiments, tunneling charge transport between a superconductor and a normal metal becomes exponentially suppressed, and zero-bias resistance diverges, as the temperature is reduced and the energy gap of the superconductor grows larger than the thermal energy. Here we demonstrate that this physical phenomenon strongly impacts transport properties of inhomogeneous superconductors made of weakly coupled islands with fluctuating values of the critical temperature. We observe a non-monotonous dependence of the chain resistance on both temperature and magnetic field, with a pronounced resistance peak at temperatures at which some but not all islands are superconducting. We explain this phenomenon by the inhomogeneity of the chains, in which neighboring superconducting islands have slightly different critical temperatures. We argue that the Giaever's resistance divergence can also occur in the zero-temperature limit. Such quantum transition can occur if the magnetic field is tuned such that it suppresses superconductivity in the islands with the weaker critical field, while the islands with stronger energy gap remain superconducting. In such a field, the system acts as a chain of S-I-N junctions.

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