Gramich J, Baumgartner A, Schönenberger C
Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
Phys Rev Lett. 2015 Nov 20;115(21):216801. doi: 10.1103/PhysRevLett.115.216801. Epub 2015 Nov 16.
We report the observation of two fundamental subgap transport processes through a quantum dot (QD) with a superconducting contact. The device consists of a carbon nanotube contacted by a Nb superconducting and a normal metal contact. First, we find a single resonance with position, shape, and amplitude consistent with the theoretically predicted resonant Andreev tunneling (AT) through a single QD level. Second, we observe a series of discrete replicas of resonant AT at a separation of ~145 μeV, with a gate, bias, and temperature dependence characteristic for boson-assisted, inelastic AT, in which energy is exchanged between a bosonic bath and the electrons. The magnetic field dependence of the replica's amplitudes and energies suggest that two different bosons couple to the tunnel process.
我们报告了通过一个具有超导接触的量子点（QD）观察到的两种基本的亚能隙输运过程。该器件由一根与铌超导和普通金属接触相连的碳纳米管组成。首先，我们发现了一个单一的共振，其位置、形状和幅度与理论预测的通过单个量子点能级的共振安德列夫隧穿（AT）一致。其次，我们观察到一系列共振AT的离散副本，间隔约为145微电子伏特，具有玻色子辅助的非弹性AT的栅极、偏置和温度依赖性特征，其中能量在玻色子库和电子之间交换。副本的幅度和能量对磁场的依赖性表明，两种不同的玻色子与隧穿过程耦合。
