论文标题
超导体中的量子相变 - 量子 - 螺旋体约瑟夫森结构，具有吸引人的内部交互作用
Quantum phase transitions in superconductor--quantum-dot--superconductor Josephson structures with attractive intradot interaction
论文作者
论文摘要
从理论上讲，当电子之间的内部相互作用具有吸引力时，我们在量子点上耦合到两个超导导线的量子点中的超导接近效应。由于超导接近效应，嵌入式量子点的电子状态是具有奇数职业数量的自旋极化状态，要么是具有均匀职业数量的BCS样状态。我们表明，在存在外部磁场的情况下，系统可以表现出与职业数量相关的费米亚奇偶校验的量子相变。在这项工作中，我们采用了一种自洽的理论方法，将我们的考虑扩展到所谓的超导原子限制之外，其中假定铅的超导差距被认为是最大的能量量表。该方法使我们能够作为吸引人相互作用的结果来数值研究点的电子结构。对于从原子极限远离的制度中的能量相图，我们发现了一种恢复行为，其中量子点和铅之间的杂交强度的中间范围内存在该点的BCS样相。我们还考虑了约瑟夫森的当前阶段关系，并确定了许多示例，显示了$ 0-π$相变，这些相位可能会带来重要的切换效果。
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 work, 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. The method enables us to numerically investigate the electronic structure of the dot as results 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.
