Josephson current through a quantum dot coupled to a molecular magnet
Josephson current through a quantum dot coupled to a molecular magnet
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DOI：
10.1103/physrevb.88.104512
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发表时间：
2013-04
影响因子：
3.7
通讯作者：
P. Stadler;C. Holmqvist;W. Belzig
中科院分区：
文献类型：
--
作者：
P. Stadler;C. Holmqvist;W. Belzig
约瑟夫森电流由超导能隙内的尖锐Andreev态携带。我们从理论上研究了由一个量子点连接到两个超导导线并耦合到分子磁体的自旋的磁可调纳米结的电子输运。分子磁体和量子点之间的交换相互作用由于量子点能级的自旋相关重整化和自旋翻转的诱导而修改Andreev态。施加到量子点和分子磁体的中心区域的磁场进一步调谐约瑟夫森电流并开始分子磁体的自旋的进动。我们使用非平衡绿色函数的方法来评估结的输运性质。我们的计算揭示了量子点的能级、磁场以及分子磁体和占据量子点能级的电子之间的交换相互作用可以触发约瑟夫森结从0到$\ensuremath{\pi}$态的跃迁。由磁场引起的占据态的重新分布强烈地改变了电流-相位关系。的临界电流表现出急剧增加的功能的能量水平的点，磁场，或交换相互作用。
Josephson currents are carried by sharp Andreev states within the superconducting energy gap. We theoretically study the electronic transport of a magnetically tunable nanoscale junction consisting of a quantum dot connected to two superconducting leads and coupled to the spin of a molecular magnet. The exchange interaction between the molecular magnet and the quantum dot modifies the Andreev states due to a spin-dependent renormalization of the quantum dot's energy level and the induction of spin flips. A magnetic field applied to the central region of the quantum dot and the molecular magnet further tunes the Josephson current and starts a precession of the molecular magnet's spin. We use a nonequilibrium Green's function approach to evaluate the transport properties of the junction. Our calculations reveal that the energy level of the dot, the magnetic field, and the exchange interaction between the molecular magnet and the electrons occupying the energy level of the quantum dot can trigger transitions from a 0 to a $\ensuremath{\pi}$ state of the Josephson junction. The redistribution of the occupied states induced by the magnetic field strongly modifies the current-phase relation. The critical current exhibits a sharp increase as a function of either the energy level of the dot, the magnetic field, or the exchange interaction.