耦合Majorana束缚态T形双量子点中的Andreev反射  

Andreev reflection in a T-shaped double quantum-dot with coupled Majorana bound states

作　　者：王素新[1,2] 李玉现[1] 王宁[1] 刘建军[1,3] 

机构地区：[1]河北师范大学物理科学与信息工程学院,河北省新型薄膜材料实验室,石家庄050024 [2]河北民族师范学院物理与电子工程学院,承德067000 [3]石家庄学院物理系,石家庄050035

出　　处：《物理学报》2016年第13期233-239,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61176089,10974043);河北省自然科学基金(批准号:A2011205092,2014205005);河北民族师范学院科学技术研究项目(批准号:201109)资助的课题~~

摘　　要：研究了连接在正常金属电极和超导电极之间的耦合Majorana束缚态(MBSs)T形双量子点结构中的Andreev反射.研究发现,对于T形双量子点结构,当入射能量等于边耦合量子点能级时Andreev反射电导出现Fano振荡,连接MBSs之后,零费米能附近出现一对新的Fano型振荡峰.如果忽略两个MBSs之间的相互作用,零费米能点的Andreev反射电导为定值1/2G_0(G_0=2e^2/h),不受量子点能级、双量子点之间耦合强度以及量子点与MBSs之间的耦合强度的影响.此外,在没有耦合MBSs的T形双量子点结构中,调节双量子点间的耦合强度可以使零费米能附近的Andreev反射电导出现由共振带向反共振带的转变,而耦合MBSs之后,又可以使反共振消失转而出现新的共振峰.Owing to their potential applications in topological quantum computation and because of their fundamental interest,Majorana fermions are currently attracting increasing attention. Numerous theoretical and experimental studies exactly show that the quantum dot（QD） structure is a good candidate for the detection of Majorana bound state（MBSs）. QD system has many unique transport properties and interesting quantum phenomena, such as quantum interference effect,Fano effect, etc. In addition, compared with a single QD, a coupled QD structure has many adjustable parameters,and thus has more important theoretical and practical value, which provides an excellent platform to detect MBSs. In addition, QD coupled with normal metallic conductor and with superconducting electrode structure exhibits interesting transport properties. One of these properties is the so-called Andreev reflection（AR）. Especially, in the subgap regime,the current almost entirely originates from the anomalous Andreev channel; such spectroscopy can thus directly probe any in-gap state. In the present paper, we consider a T-shaped double QD structure with side-coupled to MBSs and investigate the transport properties through the system by adding a normal and a superconducting lead. We calculate the AR conductance through the system in the subgap transport. Here we focus on the effects of MBSs on AR through the system. We find that the AR conductance presents a resonant peak around zero Fermi energy when only one QD（QD_1） connects to metal and superconducting leads. As a consequence of quantum interference, when using another QD_2 side-attached to QD_1, a pair of new Fano-type resonant peaks appear and is distributed aside the zero point and the Fano antiresonant point is at the energy level of the QD_2. If an MBS is introduced to couple to QD_2, the AR conductance shows several new features. First, a pair of new Fano-type resonance curves appears and the original ones also persist except for the position shifting. In addition, the AR cond

关 键 词：Majorana束缚态 双量子点 ANDREEV反射 Fano效应 

分 类 号：O471.1[理学—半导体物理]