We consider two interacting quantum dots coupled by standard superconductors. We derive an effective Hamiltonian, and show that over a wide parameter range a degenerate ground state can be obtained. An exotique form of Majorana bound states are supported at these degeneracies, and the system can be adiabatically tuned to a limit in which it is equivalent to the one-dimensional wire model of Kitaev. We give the form of a Majorana bound state in this system in the strong interaction limit in the many-particle picture. We also study the Josephson current in this system, and demonstrate that a double slit-like pattern emerges in the presence of an extra magnetic field. This pattern is shown to disappear with increasing interaction strength, which is able to be explained as the current being carried by chargeless Majorana modes.
我们讨论了耦合到几个单独可调量子点的Kitaev线网络，作为最近关于耦合到承载Majorana零模式的纳米线的量子点的实验的扩展[Deng et al. Science 354 1557（2016）and Deng et al. arXiv：1712.03536（2017）]。该装置具有精确零能量的局部马约拉纳模式，我们表明它们可以通过单独作用于量子点来操纵。通过将三根线排列成三结，可以得到编织过程，并且量子点的电荷读出可以用来揭示Majorana零模的非阿贝尔统计。该设置可以扩大规模，以满足拓扑量子计算的更高级目的。
We investigate theoretically the thermoelectric transport properties of a T-shaped double quantum dot side-coupled to a topological superconducting nanowire hosting Majorana zero-energy modes. The calculations are performed using the numerical renormalization group method focusing on the transport regime, where the system exhibits the two-stage Kondo effect. It is shown that the leakage of Majorana quasiparticles into the double dot system results in a half-suppression of the second stage of the Kondo effect, which is revealed through fractional values of the charge and heat conductances and g…
We investigate the transport properties through a nanostructure composed of parallel double quantum dots coupled to two normal contacts. Additionally, each quantum dot is connected to a topological superconducting nanowire, hosting Majorana zero modes at its ends. A magnetic flux threading across the area enclosed by the interferometer is considered. First, we investigate the physical quantities of the system employing Green's function formalism. We find that the emergence of bound states appears in symmetric configurations of topological superconducting nanowires, i.e., depending on their len…
Effect of Interdots Electronic Repulsion in the Majorana Signature for a Double Dot Interferometer
我们从理论上研究了两个量子点之间存在库仑排斥的马约拉纳标志的特征，描述了一个无自旋的Aharonov-Bohm干涉仪，其中一个量子点强烈耦合到拓扑相位内的Kitaev线。这种系统最初在J. of Appl.Phys.116，173701（2014）中提出，没有库仑相互作用。我们的研究结果表明，对于点的共振，库仑排斥和点线耦合的强度之间的比率改变的马约拉纳零偏置峰的宽度为两个法诺制度研究，从而表明，电子interdot相关性影响的马约拉纳状态的寿命在点与线杂交。此外，对于非共振的情况下，点的能级之间的交换也修改了Majorana峰的宽度，这不会发生在非相互作用的情况下。这里得到的结果可以指导实验者，追求一种方法来揭示马约拉纳签名。
We propose and theoretically investigate an alternative way to create the poor man's Majorana bound states (MBSs) introduced in Phys. Rev. B 86, 134528 (2012). Our proposal is based on two quantum dots (QDs) with strong electron-electron interactions that couple via a central QD with proximity-induced superconductivity. In the presence of spin-orbit coupling and a magnetic field, gate control of all three QDs allows tuning the system into sweet spots with one MBS localized on each outer dot. We quantify the quality of these MBSs and show how it depends on the Zeeman energy and interaction stre…
Majorana Fermions in spin up and down electronic complexes in spin-orbit coupled array of semiconductor quantum dots in proximity to $s$-type superconductor and in magnetic field
University of Ottawa（渥太华大学）；Memorial University of Newfoundland and Labrador（纽芬兰与拉布拉多纪念大学）
Probing charge noise in bilayer graphene quantum dots by Landau-Zener-Stückelberg-Majorana spectroscopy
RWTH Aachen University（亚琛工业大学）；JARA-FIT；nd Institute of Physics, RWTH Aachen University（亚琛工业大学第二物理研究所）；Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich（于利希研究中心彼得·格林伯格研究所（PGI-9））；Forschungszentrum Jülich（于利希研究中心）；CST - Compound Semiconductor Technology, RWTH Aachen University（亚琛工业大学化合物半导体技术）；University of Vienna, Faculty of Physics（维也纳大学物理系）；National Institute for Materials Science（国立材料研究所）
We investigate the spectral and transport properties of a double quantum dot laterally attached to a topological superconducting nanowire, hosting the Majorana zero-energy modes. Specifically, we consider a geometry, in which the outer quantum dot is embedded between the external normal and superconducting leads, forming a circuit. First, we derive analytical expressions for the bound states in the case of an uncorrelated system and discuss their signatures in the tunneling spectroscopy. Then, we explore the case of strongly correlated quantum dots by performing the numerical renormalization g…
Unveiling Majorana Quasiparticles by a Quantum Phase Transition: Proposal of a Current Switch
我们提出了一种理论方法的基础上构成的干涉仪由两个量子点不对称耦合到孤立的马约拉纳准粒子（MQPs），躺在两个拓扑Kitaev链的边缘，分别通过耦合$(t+Δ)$和$(Δ-t)$。这种设置使我们能够以一种与零偏置峰值特征截然不同的方式探测MQPs。（i）对于连接到两个链的上部点，装置将两个MQP感知为普通费米子，并且电流仅穿过下部点，因为上部点中的电流由于超导能隙的存在而被阻止;和（ii）通过稍微抑制上面的点与一条链的杂交，电流突然切换到流过这个点，一旦被捕获的电子作为连续体（BIC）中的束缚态，（Phys. Rev. B 93，165116（2016））出现在下面的点中。这种在上点和下点之间的电流切换表征了这里提出的量子相变（QPT），其是转变的控制参数$t/Δ$的比率。该QPT与从普通的费米子激发制度到干涉仪中的MQP的变化相关联，这使得不仅能够基本揭示MQP，而且还产生由它们辅助的电流开关。
Topological orders have been intrinsically identified in a class of systems such as fractional quantum Hall states and spin liquids. Accessing such states often requires extreme conditions such as low temperatures, high magnetic fields, pure samples, etc. Another approach would be to engineer the topological orders in systems with more accessible ingredients. In this work, we present networks of Majorana bound states, which are currently accessible in semiconductor nanowires proximitized to conventional superconductors, and show that the effective low-energy theory is topologically ordered. We…
Kitaev chain is a theoretical model of a one-dimensional topological superconductor with Majorana zero modes at the two ends of the chain. With the goal of emulating this model, we build a chain of three quantum dots in a semiconductor nanowire. We observe Andreev bound states in each of the three dots and study their magnetic field and gate voltage dependence. Theory indicates that triple dot states acquire Majorana polarization when Andreev states in all three dots reach zero energy in a narrow range of magnetic field. In our device Andreev states in one of the dots reach zero energy at a lo…
