Zhang Po, Wu Hao, Chen Jun, Khan Sabbir A, Krogstrup Peter, Pekker David, Frolov Sergey M
Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
Department of Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
Phys Rev Lett. 2022 Jan 28;128(4):046801. doi: 10.1103/PhysRevLett.128.046801.
We investigate 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 Al lead in an InAs nanowire. The quantum dot closest to the normal lead exhibits Coulomb diamonds, and 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 use Andreev or Majorana states.
我们研究了一种电子输运阻塞机制，其中位于电流路径中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，在砷化铟纳米线中的超导铝引线附近通过静电作用创建了一个双量子点。最靠近正常引线的量子点呈现出库仑菱形，而最靠近超导引线的量子点呈现出安德烈夫束缚态和诱导能隙。实验观测结果与一种名为安德烈夫阻塞的理论模型吻合良好，之所以这样命名是因为三重态双量子点构型抑制了安德烈夫反射。观测到的泄漏电流可以用有限温度来解释。我们观测到了高电流下预测的四重能级简并点以及由正常量子点的占据情况控制的周期性电导模式。随着温度和磁场的增加，奇偶输运不对称性消失。这种阻塞现象可用于研究超导体的自旋结构。它也可能在使用安德烈夫态或马约拉纳态的量子计算设备中找到用途。
