混合 InSb-Al 库仑岛超导基态中的奇偶转变。
Parity transitions in the superconducting ground state of hybrid InSb-Al Coulomb islands.
机构信息
QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA, Delft, The Netherlands.
Microsoft Quantum, Microsoft Station Q, University of California Santa Barbara, Santa Barbara, CA, 93106, USA.
出版信息
Nat Commun. 2018 Nov 15;9(1):4801. doi: 10.1038/s41467-018-07279-7.
The number of electrons in small metallic or semiconducting islands is quantised. When tunnelling is enabled via opaque barriers this number can change by an integer. In superconductors the addition is in units of two electron charges (2e), reflecting that the Cooper pair condensate must have an even parity. This ground state (GS) is foundational for all superconducting qubit devices. Here, we study a hybrid superconducting-semiconducting island and find three typical GS evolutions in a parallel magnetic field: a robust 2e-periodic even-parity GS, a transition to a 2e-periodic odd-parity GS, and a transition from a 2e- to a 1e-periodic GS. The 2e-periodic odd-parity GS persistent in gate-voltage occurs when a spin-resolved subgap state crosses zero energy. For our 1e-periodic GSs we explicitly show the origin being a single zero-energy state gapped from the continuum, i.e., compatible with an Andreev bound states stabilized at zero energy or the presence of Majorana zero modes.
在小的金属或半导体岛屿中，电子数量是量子化的。当通过不透明势垒实现隧穿时，这个数量可以增加或减少一个整数。在超导体中，增加的是两个电子电荷（2e）的整数倍，这反映了库珀对凝聚体必须具有偶数宇称。这种基态（GS）是所有超导量子比特器件的基础。在这里，我们研究了一个混合超导-半导体岛屿，并在平行磁场中发现了三种典型的 GS 演化：一个稳定的 2e 周期性偶数宇称 GS，一个过渡到 2e 周期性奇数宇称 GS，以及一个从 2e 到 1e 周期性 GS 的转变。当自旋分辨的能隙态穿过零能量时，在栅极电压下出现的 2e 周期性奇数宇称 GS 是持久的。对于我们的 1e 周期性 GS，我们明确地表明，其起源是一个与连续谱分离的单个零能态，即与在零能量下稳定的安德烈夫束缚态或马约拉纳零模的存在兼容。
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