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首页> 外文期刊>Physical review.B.Condensed matter and materials physics >Quantum phase transitions in superconductor-quantum-dot-superconductor Josephson structures with attractive intradot interaction
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Quantum phase transitions in superconductor-quantum-dot-superconductor Josephson structures with attractive intradot interaction

机译：超导体 - 量子点超级导体Josephson结构中的量子相变，具有吸引有吸引力的内部互动

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We theoretically study the superconducting proximity effect in a quantum dot coupled to two superconducting leads when the intradot interaction between electrons is made attractive. Because of the superconducting proximity effect, the electronic states for the embedded quantum dot are either spin-polarized states with an odd occupation number or BCS-like states with an even occupation number. We show that in the presence of an external magnetic field, the system can exhibit quantum phase transitions of fermion parity associated with the occupation number. In this paper, we adopt a self-consistent theoretical method to extend our considerations beyond the so-called superconducting atomic limit in which the superconducting gap for the leads is assumed to be the largest energy scale. This method enables us to numerically investigate the electronic structure of the dot as a result of the attractive interaction. For energy phase diagrams in the regime away from the atomic limit, we find a reentrant behavior where a BCS-like phase of the dot exists in an intermediate range of the hybridization strength between the quantum dot and the leads. We also consider Josephson current-phase relations and identify a number of examples showing 0-π phase transitions that may offer important switching effects.
机译：理论上，当电子之间的内部互动使电子具有吸引力时，从理论上研究了耦合到两个超导引线的量子点中的超导接近效应。由于超导邻近效应，嵌入量子点的电子状态是自旋极化状态，具有奇数占用号码或类似于占用号码的BCS的状态。我们表明，在存在外部磁场的情况下，系统可以表现出与占用号码相关的费率奇偶校验的量子相变。在本文中，我们采用自我一致的理论方法来扩展我们的考虑因素，超出所谓的超导原子极限，其中假设引线的超导间隙是最大的能量级。该方法使我们能够在数值上以具有吸引人的相互作用的结果进行数字研究点的电子结构。对于远离原子极限的方案中的能量相图，我们发现了一种倒退行为，其中点的BCS样相位存在于量子点与引线之间的杂交强度的中间范围内。我们还考虑约瑟夫森当前相位关系，并确定显示0-π相交的示例，该示例可以提供重要的切换效果。

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  • 来源
    《Physical review.B.Condensed matter and materials physics》 |2020年第21期|214507.1-214507.10|共10页
  • 作者

    Yu-Chun Hsu; Wu-Jing Chen; Chien-Te Wu;

  • 作者单位

    Department of Electrophysics National Chiao Tung University Hsinchu Taiwan;

    Department of Electrophysics National Chiao Tung University Hsinchu Taiwan;

    Department of Electrophysics National Chiao Tung University Hsinchu Taiwan Physics Division National Center for Theoretical Sciences Hsinchu Taiwan;

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