Anomalous Zero-Bias Conductance Peak in a Nb-InSb Nanowire-Nb Hybrid Device
Anomalous Zero-Bias Conductance Peak in a Nb-InSb Nanowire-Nb Hybrid Device
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DOI：
10.1021/nl303758w
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发表时间：
2012-12-01
期刊：
影响因子：
10.8
通讯作者：
Xu, H. Q.
中科院分区：
文献类型：
--
作者：
Deng, M. T.;Yu, C. L.;Xu, H. Q.
半导体InSb纳米线有望为固态系统中Majorana费米子的研究提供一个良好的材料平台。在这里，我们报告的实现的Nb-InSb碲-Nb混合量子器件和零偏压电导峰结构的设备中的观察。InSb纳米线量子点形成在两个Nb接触之间的器件中。由于邻近效应，由超导体Nb接触覆盖的InSb纳米线段变成具有类似于0.25 meV的超导能隙Δ（InSb）的超导体。观察到一个可调的临界超电流在器件中的高背栅电压区，其中的费米能级在InSb纳米线位于量子点的隧道势垒以上，该设备是开放的传导。当一个垂直的磁场被施加到设备，临界超电流被认为是随着磁场的增加而减少。然而，在足够低的背栅电压下，器件表现出准粒子库仑阻塞特性，即使在零磁场下，超导电流也被强烈抑制。当将比临界值强的垂直磁场施加到器件上时，这种传输特性发生变化，在临界值处，InSb纳米线中的塞曼能量为E-z，类似于Delta（Insb）。在这种情况下，运输测量显示在零偏置电压和整个InSb纳米线在设备中的行为作为一个拓扑超导体相的电导峰。我们还表明，这种零偏置电导峰结构可以持续在很大的范围内施加的磁场，可以解释为在InSb纳米线的马约拉纳费米子的运输签名。
Semiconductor InSb nanowires are expected to provide an excellent material platform for the study of Majorana fermions in solid state systems. Here, we report on the realization of a Nb-InSb nanowire-Nb hybrid quantum device and the observation of a zero-bias conductance peak structure in the device. An InSb nanowire quantum dot is formed in the device between the two Nb contacts. Due to the proximity effect, the InSb nanowire segments covered by the superconductor Nb contacts turn to superconductors with a superconducting energy gap Delta(InSb) similar to 0.25 meV. A tunable critical supercurrent is observed in the device in high back gate voltage regions in which the Fermi level in the InSb nanowire is located above the tunneling barriers of the quantum dot and the device is open to conduction. When a perpendicular magnetic field is applied to the devices, the critical supercurrent is seen to decrease as the magnetic field increases. However, at sufficiently low back gate voltages, the device shows the quasi-particle Coulomb blockade characteristics and the supercurrent is strongly suppressed even at zero magnetic field. This transport characteristic changes when a perpendicular magnetic field stronger than a critical value, at which the Zeeman energy in the InSb nanowire is E-z similar to Delta(Insb), is applied to the device. In this case, the transport measurements show a conductance peak at the zero bias voltage and the entire InSb nanowire in the device behaves as in a topological superconductor phase. We also show that this zero-bias conductance peak structure can persist over a large range of applied magnetic fields and could be interpreted as a transport signature of Majorana fermions in the InSb nanowire.