Interplay of disorder and interaction in Majorana quantum wires
Alejandro M. Lobos, Roman M. Lutchyn, S. Das Sarma
备注:
New version includes a section and an appendix with a detailed study on the effect of interaction and disorder on the stability of Majorana end-states. 6 pages, 1 figure
We study the interplay between disorder and interaction in one-dimensional topological superconductors which carry localized Majorana zero-energy states. Using Abelian bosonization and the perturbative renormalization group (RG) approach, we obtain the RG-flow and the associated scaling dimensions of the parameters and identify the critical points of the low-energy theory. We predict a quantum phase transition from a topological superconducting phase to a non-topological localized phase, and obtain the phase boundary between these two phases as a function of the electron-electron interaction and the disorder strength in the nanowire. Based on an instanton analysis which incorporates the effect of disorder, we also identify a large regime of stability of the Majorana-carrying topological phase in the parameter space of the model.
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…
In this work we investigate Majorana correlations in quantum impurities coupled to a topological superconducting wire. By employing a density matrix renormalization group approach, we have calculated the Majorana correlation functions in the ground state of the system for different positions of the impurities along the wire. We observe that the correlations decreases exponentially with the distance between the impurities and the ends of the wire. Moreover, different electron-electron interactions on the wire and on the impurities were also analyzed, and the results showed a stronger effect as …
The signatures of Majorana zero-energy mode leaking into a spin-charge entangled double quantum dot are investigated theoretically in the strong electron correlation regime. The considered setup consists of two capacitively coupled quantum dots attached to external contacts and side-attached to topological superconducting wire hosting Majorana quasiparticles. We show that the presence of Majorana mode gives rise to unique features in the local density of states in the $SU(4)$ Kondo regime. Moreover, it greatly modifies the gate voltage dependence of the linear conductance, leading to fractiona…
Interplay between classical magnetic moments and superconductivity in quantum one-dimensional conductors: toward a self-sustained topological Majorana phase
We propose and investigate a simple one-dimensional model for a single-channel quantum wire hosting electrons that interact repulsively and are subject to a significant spin-orbit interaction. We show that an external Zeeman magnetic field, applied at the right angle to the Rashba spin-orbit axis, drives the wire into a correlated spin-density wave state with gapped spin and gapless charge excitations. By computing the ground-state degeneracies of the model with either (anti-)periodic or open boundary conditions, we conclude that the correlated spin-density state realizes a gapless symmetry-pr…
A recent experiment [Mourik et al., Science 336, 1003 (2012)] on InSb quantum wires provides possible evidence for the realization of a topological superconducting phase and the formation of Majorana bound states. Motivated by this experiment, we consider the signature of Majorana bound states in the differential tunneling conductance of multi-subband wires. We show that the weight of the Majorana-induced zero-bias peak is strongly enhanced by mixing of subbands, when disorder is added to the end of the quantum wire. We also consider how the topological phase transition is reflected in the gap…
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 study Majorana zero modes properties in cylindrical cross-section semiconductor quantum wires based on the $k \cdot p$ theory and a discretized lattice model. Within this model, the influence of disorder potentials in the wire and amplitude and phase fluctuations of the superconducting order-parameter are discussed. We find that for typical wire geometries, pairing potentials, and spin-orbit coupling strengths, coupling between quasi-one-dimensional sub-bands is weak, low-energy quasiparticles near the Fermi energy are nearly completely spin-polarized, and the number of electrons in the act…
Twisted bilayer graphene (TBG) realizes a highly tunable, strongly interacting system featuring superconductivity and various correlated insulating states. We establish gate-defined wires in TBG with proximity-induced spin-orbit coupling as $(i)$ a tool for revealing the nature of correlated insulators and $(ii)$ a platform for Majorana-based topological qubits. In particular, we show that the band structure of a gate-defined wire immersed in an `inter-valley coherent' correlated insulator inherits electrically detectable fingerprints of symmetry breaking native to the latter. Surrounding the …
Equivalent topological invariants for one-dimensional Majorana wires in symmetry class D
一维拓扑超导体的两端只有一个马约拉纳束缚态,它与普通能隙系统的区别在于Z_2拓扑不变量。最初,这个不变量是由Kitaev根据哈密顿量的马约拉纳表示的Pfuman计算的:Pfuman的符号将马约拉纳费米子的所有有间隙的二次形式的集合分成两个不等价的类。在更熟悉的Bogoliubov de Gennes平均场超导描述中,出现的粒子空穴对称性产生了量子化的Zak-Berry相位,其值也是拓扑不变量。在这项工作中,我们明确地表明这两个配方的等价性,将它们都相绕组的变换矩阵,使其约旦正规形式的哈密尔顿的马约拉纳表示矩阵。
We study coherent electronic transport through a Coulomb blockaded superconducting Rashba wire in the co-tunneling regime between conductance resonances. By varying an external Zeeman field the wire can be tuned into a topological regime, where non-local transport through Majorana zero modes is the dominant mechanism. We model coherent transport in the co-tunneling regime by using a scattering matrix formalism, and find that the transmission amplitude has a maximum as a function of Zeeman field, whose height is proportional to the wire length. We relate the transmission amplitude to the Majora…
Theoretically, a pair of Majorana bound states in a topological superconductor forms a single fermionic level even at large separations, implying that the parity information is stored nonlocally. The nonlocality leads to a long-distance coherence for electrons tunneling through a Coulomb blockaded Majorana wire [Fu, Phys. Rev. Lett. 104, 056402 (2010)], an effect that can be observed, e.g., in an interferometer. Here, we examine theoretically the coherent electron transfer, taking into account that tunneling implies the long-distance transfer of charge, which is carried by one-dimensional plas…
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。
In one-dimensional topological superconductors driven periodically with the frequency $ω$, two types of topological edge modes may appear, the well-known Majorana zero mode and a Floquet Majorana mode located at the quasi-energy $\hbar ω/2$. We investigate two Josephson-coupled topological quantum wires in the presence of Coulomb interactions, forming a so-called Majorana box qubit. An oscillating gate voltage can induce Floquet Majorana modes in both wires. This allows encoding 3 qubits in a sector with fixed electron parity. If such a system is prepared by increasing the amplitude of oscilla…