AI 中文总结
本文理论研究非对称耦合量子点-拓扑超导纳米线结的量子输运，分析马约拉纳束缚态未杂化与杂化时，不对称参数α、q及温度等对线性电导的影响，明确不对称参数对马约拉纳束缚态输运 signature 观测的关键作用。
AI 中文摘要
我们对一种纳米尺度系统中的量子输运进行理论研究，该系统包含一个中心量子点（QD），其与正常引线非对称耦合，同时还与两个马约拉纳束缚态（MBSs）耦合，这两个马约拉纳束缚态定域在受可调磁通量调控的拓扑超导纳米线两端。我们考虑了引线-QD耦合不对称参数α和偏置电压不对称参数q对系统线性电导的影响，分别针对马约拉纳束缚态未杂化和杂化的两种情况展开分析。在零温度极限下，对于未杂化的马约拉纳束缚态，系统的线性电导仅在磁通量相位φ=(2n+1)π（n∈ℤ）时为有限值，其表达式为𝒢=2qαe²/[h(α+1)]；而对于杂化的马约拉纳束缚态，线性电导则呈现出对系统参数的复杂依赖关系。在有限温度下，对于未杂化的马约拉纳束缚态，系统的线性电导随磁通量相位φ的振荡周期为2π，且仅需改变偏置电压不对称参数q的值，即可将线性电导最大值的位置从φ=2nπ偏移至φ=(2n+1)π。对于杂化的马约拉纳束缚态，当中心QD的能级ε_d被调至引线的费米能级（ε_d=ε_F）时，电导呈现出类似的振荡行为；不过当ε_d≠ε_F时，振荡周期变为4π，且线性电导最大值的位置取决于ε_d的实际值及系统中的其他参数。我们的研究结果凸显了引线-QD和偏置电压不对称参数的实验重要性，这些参数普遍存在于实际实验装置中，且会强烈影响马约拉纳束缚态输运 signature 的识别与观测。
英文摘要
We present a theoretical study of the quantum transport through a nanoscale system in which a central quantum dot (QD) is coupled asymmetrically to normal leads and to two Majorana bound states (MBSs) localized at the ends of a topological superconducting nanowire threaded by a tunable magnetic flux. The effects of the leads--QD coupling asymmetry parameter $α$ and the bias voltage asymmetry parameter $q$ on the system's linear conductance are considered for the case of unhybridized and hybridized MBSs. In the zero-temperature limit, for unhybridized MBSs the system's linear conductance is finite only when the magnetic flux phase $ϕ= (2n+1)π$ ($n\in\mathbb{Z}$) and it scales as $\mathcal{G}=2qαe^2/[h(α+1)]$, while for hybridized MBSs it presents a complicated dependence on the system's parameters. At finite temperature, for unhybridized MBSs, the system's linear conductance oscillates as a function of the magnetic flux phase $ϕ$ with a period of $2π$, and the position of the linear conductance maxima can be shifted from $ϕ=2nπ$ to $ϕ=(2n+1)π$ by simply varying the value of the bias voltage asymmetry parameter $q$. For hybridized MBSs, the conductance exhibits a similar behavior when the energy level of the central QD, $\varepsilon_d$, is tuned at the leads' Fermi level ($\varepsilon_d=\varepsilon_F$), although when $\varepsilon_d\neq\varepsilon_F$ the oscillation period changes to $4π$, and the position of the linear conductance maxima depends on the actual value of $\varepsilon_d$ and other parameters in the system. Our results highlight the experimental importance of the leads-QD and bias voltage asymmetry parameters, which are often present in realistic experimental setups, and can strongly affect the identification and observation of MBSs transport signatures.
Comments19 pages, 15 figures
