Magnetic-field-induced transition in a quantum dot coupled to a superconductor
Magnetic-field-induced transition in a quantum dot coupled to a superconductor
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DOI：
10.1103/physrevresearch.2.012065
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发表时间：
2019-12
影响因子：
4.2
通讯作者：
A. García Corral;D. V. van Zanten;K. Franke;H. Courtois;S. Florens;C. Winkelmann
中科院分区：
文献类型：
--
作者：
A. García Corral;D. V. van Zanten;K. Franke;H. Courtois;S. Florens;C. Winkelmann
量子点的磁矩可以通过其与超导库的耦合来屏蔽，这取决于超导能隙的层次结构和相关的Kondo尺度。这种屏蔽-非屏蔽转变可以由静电门控、隧道耦合和磁场驱动。利用电迁移技术研究了非对称超导体-量子点-超导体（S-QD-S）结屏蔽-非屏蔽跃迁附近的亚能隙激发谱。我们的测量结果揭示了一个重入相边界之间的竞争所确定的塞曼能量和间隙减少与磁场。我们进一步跟踪的相变随温度的升高，这也证明了热副本的subgap状态的演变。
The magnetic moment of a quantum dot can be screened by its coupling to a superconducting reservoir, depending on the hierarchy of the superconducting gap and the relevant Kondo scale. This screening-unscreening transition can be driven by electrostatic gating, tunnel coupling, and, as we demonstrate here, magnetic field. We perform high-resolution spectroscopy of subgap excitations near the screening-unscreening transition of asymmetric superconductor - quantum dot - superconductor (S-QD-S) junctions formed by the electromigration technique. Our measurements reveal a re-entrant phase boundary determined by the competition between Zeeman energy and gap reduction with magnetic field. We further track the evolution of the phase transition with increasing temperature, which is also evidenced by thermal replicas of subgap states.