arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 2007.00357cond-mat.mes-hallcond-mat.supr-con
收藏

一维自旋轨道耦合Dirac系统的扩展$s$波超导性:Majorana模和Josephson效应

One-dimensional spin-orbit coupled Dirac system with extended $s$-wave superconductivity: Majorana modes and Josephson effects

Adithi Udupa, Abhishek Banerjee, K. Sengupta, Diptiman Sen

摘要:

受拓扑绝缘体边界电子自旋动量锁定的启发,我们研究了一维自旋轨道耦合无质量Dirac电子与$s$波超导配对系统.由于自旋-轨道耦合,我们的模型只有两种线性色散模式,我们把它们看作是向右运动的自旋向上和向左运动的自旋向下。晶格和连续模型进行了研究。在格点模型中,我们发现,一个单一的马约拉纳零能量模式出现在有限系统的每一端,只要$s$波配对具有扩展的形式,与最近邻配对大于现场配对。我们确认这两个数值和分析计算的绕组数。接下来,我们研究了一个具有薛定谔和狄拉克类项的模型的格点版本,发现该模型在拓扑平凡和非平凡相之间存在拓扑转变,这取决于薛定谔和狄拉克项的相对强度。然后,我们研究了一个连续系统组成的两个$s$波超导体与不同相位的配对。值得注意的是,我们发现该系统有一个{\it单一} Andreev束缚态,这是本地化的交界处。当配对相位差跨越$2 π$的倍数时,Andreev束缚态接触超导能隙的顶部并消失,并且从能隙的底部出现不同的状态。我们还研究了在这样的结的交流约瑟夫森效应的电压偏置,既有一个常数$V_0$和一个长期的振荡频率$ω$。我们发现,与标准的约瑟夫森结,夏皮罗高原出现时,约瑟夫森频率$ω_J= 2eV_0/\hbar$是一个合理的分数$ω$。我们讨论的实验,可以实现这样的路口。

英文摘要:

Motivated by the spin-momentum locking of electrons at the boundaries of topological insulators, we study a one-dimensional system of spin-orbit coupled massless Dirac electrons with $s$-wave superconducting pairing. As a result of the spin-orbit coupling, our model has only two kinds of linearly dispersing modes, which we take to be right-moving spin-up and left-moving spin-down. Both lattice and continuum models are studied. In the lattice model, we find that a single Majorana zero energy mode appears at each end of a finite system provided that the $s$-wave pairing has an extended form, with the nearest-neighbor pairing being larger than the on-site pairing. We confirm this both numerically and analytically by calculating the winding number. Next we study a lattice version of a model with both Schrödinger and Dirac-like terms and find that the model hosts a topological transition between topologically trivial and non-trivial phases depending on the relative strength of the Schrödinger and Dirac terms. We then study a continuum system consisting of two $s$-wave superconductors with different phases of the pairing. Remarkably, we find that the system has a {\it single} Andreev bound state which is localized at the junction. When the pairing phase difference crosses a multiple of $2 π$, an Andreev bound state touches the top of the superconducting gap and disappears, and a different state appears from the bottom of the gap. We also study the AC Josephson effect in such a junction with a voltage bias that has both a constant $V_0$ and a term which oscillates with a frequency $ω$. We find that, in contrast to standard Josephson junctions, Shapiro plateaus appear when the Josephson frequency $ω_J= 2eV_0/\hbar$ is a rational fraction of $ω$. We discuss experiments which can realize such junctions.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑