scholarly journals Creating Majorana modes from segmented Fermi surface

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Michał Papaj ◽  
Liang Fu
Keyword(s):  
Quantum Confinement ◽  
Bound States ◽  
Andreev Reflection ◽  
Chemical Potential ◽  
Fine Tuning ◽  
Zeeman Field ◽  
Majorana Bound States ◽  
Magnetic Insulators ◽  
Fertile Ground ◽  
Majorana Modes

AbstractMajorana bound states provide a fertile ground for both investigation of fundamental phenomena as well as for applications in quantum computation. However, despite enormous experimental and theoretical efforts, the currently available Majorana platforms suffer from a multitude of issues that prevent full realization of their potential. Therefore, improved Majorana systems are still highly sought after. Here we present a platform for creating Majorana bound states from 2D gapless superconducting state in spin-helical systems under the in-plane magnetic or Zeeman field. Topological 1D channels are formed by quantum confinement of quasiparticles via Andreev reflection from the surrounding fully gapped superconducting region. Our proposal can be realized using narrow strips of magnetic insulators on top of proximitized 3D topological insulators. This setup has key advantages that include: small required fields, no necessity of fine-tuning of chemical potential, removal of the low-energy detrimental states, and large attainable topological gap.

scholarly journals Majorana/Andreev crossover and the fate of the topological phase transition in inhomogeneous nanowires

2021 ◽  
Author(s):  
Pasquale Marra ◽  
Angela Nigro
Keyword(s):  
Bound States ◽  
Transition Probabilities ◽  
Topological Invariants ◽  
Length Scale ◽  
Topological Phase ◽  
Andreev Bound States ◽  
Majorana Bound States ◽  
Topological Phase Transition ◽  
Majorana Modes ◽  
Global And Local

Abstract Majorana bound states (MBS) and Andreev bound states (ABS) in realistic Majorana nanowires setups have similar experimental signatures which make them hard to distinguishing one from the other. Here, we characterize the continuous Majorana/Andreev crossover interpolating between fully-separated, partially-separated, and fully-overlapping Majorana modes, in terms of global and local topological invariants, fermion parity, quasiparticle densities, Majorana pseudospin and spin polarizations, density overlaps and transition probabilities between opposite Majorana components. We found that in inhomogeneous wires, the transition between fully-overlapping trivial ABS and nontrivial MBS does not necessarily mandate the closing of the bulk gap of quasiparticle excitations, but a simple parity crossing of partially-separated Majorana modes (ps-MM) from trivial to nontrivial regimes. We demonstrate that fully-separated and fully-overlapping Majorana modes correspond to the two limiting cases at the opposite sides of a continuous crossover: the only distinction between the two can be obtained by estimating the degree of separations of the Majorana components. This result does not contradict the bulk-edge correspondence: Indeed, the field inhomogeneities driving the Majorana/Andreev crossover have a length scale comparable with the nanowire length, and therefore correspond to a nonlocal perturbation which breaks the topological protection of the MBS.

scholarly journals Delocalisation of Majorana quasiparticles in plaquette–nanowire hybrid system

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Aksel Kobiałka ◽  
Tadeusz Domański ◽  
Andrzej Ptok
Keyword(s):  
Bound States ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Two Dimensional ◽  
Edge States ◽  
Zero Energy ◽  
One Dimensional ◽  
Majorana Bound States ◽  
Entire Structure ◽  
Majorana Modes

Abstract Interplay between superconductivity, spin-orbit coupling and magnetic field can lead to realisation of the topologically non–trivial states which in finite one dimensional nanowires are manifested by emergence of a pair of zero-energy Majorana bound states. On the other hand, in two dimensional systems the chiral edge states can appear. We investigate novel properties of the bound states in a system of mixed dimensionality, composed of one-dimensional nanowire connected with two-dimensional plaquette. We study this system, assuming either its part or the entire structure to be in topologically non–trivial superconducting state. Our results show delocalisation of the Majorana modes, upon leaking from the nanowire to the plaquette with some tendency towards its corners.

Suppressed Andreev reflection and helical Andreev bound states in triplet superconductor three-dimensional topological insulator

2015 ◽  
Vol 29 (04) ◽  
pp. 1550018 ◽  
Author(s):  
M. Khezerlou ◽  
H. Goudarzi
Keyword(s):  
Topological Insulator ◽  
Bound States ◽  
Andreev Reflection ◽  
Chemical Potential ◽  
Three Dimensional ◽  
P Wave ◽  
Superconducting Gap ◽  
Tunneling Conductance ◽  
Andreev Bound States ◽  
Josephson Supercurrent

Effect of proximity-induced unconventional p-wave superconductivity in a three-dimensional topological insulator-based S/F/S structure on the Andreev bound states (ABSs) and Josephson supercurrent is studied. We investigate, in detail, the suppression of Andreev reflection and helical ABSs in the presence of three types of triplet superconducting gap. The magnetization of ferromagnetic section is perpendicular to the surface of junction. The influence of such features on the supercurrent flow on the surface of the topological insulator is studied. We carry out our goal by introducing a relevant form of Dirac spinors for gapless renormalized by chemical potential μ excitation states. Therefore, it enables us to consider the virtual Andreev process, simultaneously, and we propose to investigate it in a tunneling conductance junction. It is shown that the results obtained in this case are completely different from those in conventional superconductivity, as s- or d-waves, for example, the magnetization is found to decrease the gap for px and px+ipy case, whereas increase it for py order. Strongly suppressed Andreev reflection is demonstrated.

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

2016 ◽  
Vol 65 (13) ◽  
pp. 137302
Author(s):  
Wang Su-Xin ◽  
Li Yu-Xian ◽  
Wang Ning ◽  
Liu Jian-Jun
Keyword(s):  
Quantum Dot ◽  
Bound States ◽  
Andreev Reflection ◽  
Double Quantum ◽  
Majorana Bound States ◽  
Double Quantum Dot

Andreev Reflection in a T-Shaped Double-Quantum-Dot Structure Induced by Majorana Bound States

2014 ◽  
Vol 83 (3) ◽  
pp. 034706 ◽  
Author(s):  
Wei-Jiang Gong ◽  
Shu-feng Zhang ◽  
Zhi-Chao Li ◽  
Guangyu Yi ◽  
Yi-Song Zheng
Keyword(s):  
Quantum Dot ◽  
Bound States ◽  
Andreev Reflection ◽  
Double Quantum ◽  
Majorana Bound States ◽  
Double Quantum Dot

scholarly journals Plasmonic hot-electron photodetection with quasi-bound states in the continuum and guided resonances

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Wenhao Wang ◽  
Lucas V. Besteiro ◽  
Peng Yu ◽  
Feng Lin ◽  
Alexander O. Govorov ◽  
...  
Keyword(s):  
Bound States ◽  
Structural Parameters ◽  
Hybrid Structure ◽  
Fine Tuning ◽  
Hot Electrons ◽  
Hot Electron ◽  
Perfect Absorption ◽  
High Loss ◽  
Guided Mode ◽  
The Continuum

Abstract Hot electrons generated in metallic nanostructures have shown promising perspectives for photodetection. This has prompted efforts to enhance the absorption of photons by metals. However, most strategies require fine-tuning of the geometric parameters to achieve perfect absorption, accompanied by the demanding fabrications. Here, we theoretically propose a Ag grating/TiO2 cladding hybrid structure for hot electron photodetection (HEPD) by combining quasi-bound states in the continuum (BIC) and plasmonic hot electrons. Enabled by quasi-BIC, perfect absorption can be readily achieved and it is robust against the change of several structural parameters due to the topological nature of BIC. Also, we show that the guided mode can be folded into the light cone by introducing a disturbance to become a guided resonance, which then gives rise to a narrow-band HEPD that is difficult to be achieved in the high loss gold plasmonics. Combining the quasi-BIC and the guided resonance, we also realize a multiband HEPD with near-perfect absorption. Our work suggests new routes to enhance the light-harvesting in plasmonic nanosystems.

scholarly journals Topological isoconductance signatures in Majorana nanowires

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
L. S. Ricco ◽  
J. E. Sanches ◽  
Y. Marques ◽  
M. de Souza ◽  
M. S. Figueira ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Transport Properties ◽  
Spin Polarization ◽  
Bound States ◽  
Spin Asymmetry ◽  
Experimental Protocol ◽  
Zero Bias ◽  
Topological Superconductor ◽  
Hybrid Device ◽  
Majorana Bound States

AbstractWe consider transport properties of a hybrid device composed by a quantum dot placed between normal and superconducting reservoirs, and coupled to a Majorana nanowire: a topological superconducting segment hosting Majorana bound states (MBSs) at the opposite ends. It is demonstrated that if highly nonlocal and nonoverlapping MBSs are formed in the system, the zero-bias Andreev conductance through the dot exhibits characteristic isoconductance profiles with the shape depending on the spin asymmetry of the coupling between the dot and the topological superconductor. Otherwise, for overlapping MBSs with less degree of nonlocality, the conductance is insensitive to the spin polarization and the isoconductance signatures disappear. This allows to propose an alternative experimental protocol for probing the nonlocality of the MBSs in Majorana nanowires.

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