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arXiv 2102.03283cond-mat.mes-hallcond-mat.supr-con
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双量子点与超导体耦合中Andreev阻塞的证据

Evidence of Andreev blockade in a double quantum dot coupled to a superconductor

Po Zhang, Hao Wu, Jun Chen, Sabbir A. Khan, Peter Krogstrup, David Pekker, Sergey M. Frolov

摘要:

我们设计并研究了一个能够进入电子输运阻断机制的实验系统,在该机制中,位于电流路径上的自旋三重态被禁止进入自旋单重态超导体。为了稳定三重态,双量子点在InAs纳米线中的超导引线附近静电地产生。这些点随机地充满了两种自旋的电子。超导引线是分子束外延生长的铝壳。外壳在一段导线上被蚀刻掉,为双点和普通金属金引线腾出空间。最靠近正常铅的量子点呈现库仑菱形,最靠近超导铅的量子点呈现Andreev束缚态和诱导能隙。实验观测结果与Andreev阻塞的理论模型相比是有利的,之所以这样命名是因为三重态双点配置抑制了Andreev反射。所观察到的泄漏电流可以通过有限的温度来解释。我们观察到预测的四能级简并点的高电流和一个周期性的电导模式控制的占领正常点。随着温度和磁场的增加,奇偶输运不对称性被解除。这种阻塞现象可以用来研究超导体的自旋结构。它还可以在利用Andreev或Majorana状态的量子计算设备中找到实用性。

英文摘要:

We design and investigate an experimental system capable of entering an electron transport blockade regime in which a spin-triplet localized in the path of current is forbidden from entering a spin-singlet superconductor. To stabilize the triplet a double quantum dot is created electrostatically near a superconducting lead in an InAs nanowire. The dots are filled stochastically with electrons of either spin. The superconducting lead is a molecular beam epitaxy grown Al shell. The shell is etched away over a wire segment to make room for the double dot and the normal metal gold lead. The quantum dot closest to the normal lead exhibits Coulomb diamonds, the dot closest to the superconducting lead exhibits Andreev bound states and an induced gap. The experimental observations compare favorably to a theoretical model of Andreev blockade, named so because the triplet double dot configuration suppresses Andreev reflections. Observed leakage currents can be accounted for by finite temperature. We observe the predicted quadruple level degeneracy points of high current and a periodic conductance pattern controlled by the occupation of the normal dot. Even-odd transport asymmetry is lifted with increased temperature and magnetic field. This blockade phenomenon can be used to study spin structure of superconductors. It may also find utility in quantum computing devices that utilize Andreev or Majorana states.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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