基于量子自旋霍尔（QSH）的NS与SNS结中的边间背散射
Interedge backscattering in quantum spin Hall-based NS and SNS junctions
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中文总结 AI 辅助
该研究基于Bernevig–Hughes–Zhang模型等，探究量子自旋霍尔基NS与SNS结中边间耦合的微观条件，分析其对电导、约瑟夫森结及超导干涉图案的影响，为超导混合系统研究提供微观依据。
中文摘要 AI 辅助
我们研究了超导体混合结中使相对量子自旋霍尔（QSH）边发生耦合的微观条件。采用微观Bernevig–Hughes–Zhang模型与Bogoliubov–de Gennes形式体系，对NS界面处的势垒进行建模，并确定QSH边发生耦合的参数范围。在正常-超导体（NS）结中，这种耦合表现为量化零偏安德烈夫电导G=4e²/h的偏差，该偏差由势垒中的诱导能隙、势垒几何结构、界面透明度、轨道与费米速度失配、无序强度以及产生零偏峰的偏置电压所控制。随后分析了该边间耦合机制在平衡态约瑟夫森结中的影响，表明其会混合边分辨安德烈夫分支、在时间反演不变相位差φ=0和φ=π处打开能隙，并修改超导量子干涉图案。在反射对称几何结构中，两个能隙的相对大小提供了边间动力学相位的互补信息，该相位也决定了磁干涉图案中被抑制瓣的奇偶性。本研究揭示了控制实际器件中螺旋边态耦合的微观细节，及其对超导混合系统的相关影响。
英文摘要
We investigate the microscopic conditions that allow for the coupling between opposite quantum spin Hall (QSH) edges in hybrid junctions with superconductors. Using a microscopic Bernevig--Hughes--Zhang model and the Bogoliubov--de Gennes formalism, we model a potential barrier along the NS interface and identify the parameter regimes in which the QSH edges are coupled. In normal--superconductor junctions, such coupling manifests as deviations from the quantized zero-bias Andreev conductance $G=4e^2/h$. These deviations are controlled by the induced gap in the barrier, the barrier geometry, the interface transparency, orbital and Fermi-velocity mismatch, and disorder strength as well as the bias voltage leading to a zero-bias peak. We then analyze the impact of this interedge-coupling mechanism in Josephson junctions at equilibrium and show that it hybridizes the edge-resolved Andreev branches, opens gaps at the time-reversal-invariant phase differences $φ=0$ and $φ=π$, and modifies the superconducting quantum interference pattern. In a reflection-symmetric geometry, the relative sizes of the two gap openings provide complementary information about the interedge dynamical phase, which also determines the parity of the suppressed lobes in the magnetic interference pattern. This investigation sheds light on the microscopic details that control the coupling of helical edge states in actual devices and the resulting consequences for superconducting hybrid systems.
