scholarly journals Andreev bound states and current-phase relations in three-dimensional topological insulators

2013 ◽  
Vol 87 (10) ◽  
Author(s):  
M. Snelder ◽  
M. Veldhorst ◽  
A. A. Golubov ◽  
A. Brinkman
Keyword(s):  
Bound States ◽  
Topological Insulators ◽  
Three Dimensional ◽  
Phase Relations ◽  
Current Phase ◽  
Andreev Bound States

scholarly journals Skyrmion-induced bound states on the surface of three-dimensional topological insulators

2016 ◽  
Vol 119 (19) ◽  
pp. 193903 ◽  
Author(s):  
Dimitrios Andrikopoulos ◽  
Bart Sorée ◽  
Jo De Boeck
Keyword(s):  
Bound States ◽  
Topological Insulators ◽  
Three Dimensional

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 spectrum and supercurrents in nanowire-based SNS junctions containing Majorana bound states

2018 ◽  
Vol 9 ◽  
pp. 1339-1357 ◽  
Author(s):  
Jorge Cayao ◽  
Annica M Black-Schaffer ◽  
Elsa Prada ◽  
Ramón Aguado
Keyword(s):  
Bound States ◽  
Current Phase ◽  
Energy Splitting ◽  
Topological Phases ◽  
Spin Orbit Coupling ◽  
Topological Phase ◽  
Spin Orbit ◽  
Andreev Bound States ◽  
Zeeman Field ◽  
Rashba Spin

Hybrid superconductor–semiconductor nanowires with Rashba spin–orbit coupling are arguably becoming the leading platform for the search of Majorana bound states (MBSs) in engineered topological superconductors. We perform a systematic numerical study of the low-energy Andreev spectrum and supercurrents in short and long superconductor–normal–superconductor junctions made of nanowires with strong Rashba spin–orbit coupling, where an external Zeeman field is applied perpendicular to the spin–orbit axis. In particular, we investigate the detailed evolution of the Andreev bound states from the trivial into the topological phase and their relation with the emergence of MBSs. Due to the finite length, the system hosts four MBSs, two at the inner part of the junction and two at the outer one. They hybridize and give rise to a finite energy splitting at a superconducting phase difference of π, a well-visible effect that can be traced back to the evolution of the energy spectrum with the Zeeman field: from the trivial phase with Andreev bound states into the topological phase with MBSs. Similarly, we carry out a detailed study of supercurrents for short and long junctions from the trivial to the topological phases. The supercurrent, calculated from the Andreev spectrum, is 2π-periodic in the trivial and topological phases. In the latter it exhibits a clear sawtooth profile at a phase difference of π when the energy splitting is negligible, signalling a strong dependence of current–phase curves on the length of the superconducting regions. Effects of temperature, scalar disorder and reduction of normal transmission on supercurrents are also discussed. Further, we identify the individual contribution of MBSs. In short junctions the MBSs determine the current–phase curves, while in long junctions the spectrum above the gap (quasi-continuum) introduces an important contribution.

Superconducting Current-Phase Relation and Andreev Bound States in Nb/Au/YBa2Cu3Ox Josephson Heterojunctions

2003 ◽  
Vol 17 (10n12) ◽  
pp. 569-578 ◽  
Author(s):  
G. A. Ovsyannikov ◽  
P. V. Komissinski ◽  
Yu. V. Kislinski ◽  
Z. G. Ivanov
Keyword(s):  
Phase Relation ◽  
Bound States ◽  
Measurement Accuracy ◽  
Current Phase ◽  
Zero Bias ◽  
Shapiro Steps ◽  
Andreev Bound States ◽  
Conductance Peak ◽  
Zero Bias Conductance ◽  
Superconducting Current

Nb / Au / YBa 2 Cu 3 O x heterojunctions in (001) and (1 1 20)-oriented YBa 2 Cu 3 O x films have been fabricated. I-V curves of both kinds of heterojunctions show pronounced superconducting current. As affected by microwave radiation Shapiro steps at voltages hf/ 4e arise in the I-V curves of Nb / Au / YBa 2 Cu 3 O x (001) heterojunctions implying the double periodic (~ sin 2φ) superconducting current-phase relation. However, in the case of Nb / Au / YBa 2 Cu 3 O x (1 1 20) heterojunctions Shapiro steps have been observed in the I-V curves at voltages hf/ 2e only supporting a sinusoidal (~ sin φ) superconducting current-phase relation within measurement accuracy. A zero bias conductance peak associated with zero-energy Andreev bound states occurs in the I-V curve of the Nb / Au / YBa 2 Cu 3 O x (1 1 20) heterojunctions. We discuss the experimental results in terms of the d-wave symmetrical superconducting order parameter in YBCO.

scholarly journals Andreev bound states in ferromagnet-superconductor nanostructures

2003 ◽  
Vol 387 (1-2) ◽  
pp. 7-12 ◽  
Author(s):  
M. Krawiec ◽  
B.L. Györffy ◽  
J.F. Annett
Keyword(s):  
Bound States ◽  
Andreev Bound States

Direct Measurement of Current-Phase Relations in Superconductor/Topological Insulator/Superconductor Junctions

Nano Letters ◽  
2013 ◽  
Vol 13 (7) ◽  
pp. 3086-3092 ◽  
Author(s):  
Ilya Sochnikov ◽  
Andrew J. Bestwick ◽  
James R. Williams ◽  
Thomas M. Lippman ◽  
Ian R. Fisher ◽  
...  
Keyword(s):  
Direct Measurement ◽  
Topological Insulator ◽  
Phase Relations ◽  
Current Phase

scholarly journals TOPOLOGICAL INSULATOR AND THE DIRAC EQUATION

SPIN ◽  
2011 ◽  
Vol 01 (01) ◽  
pp. 33-44 ◽  
Author(s):  
SHUN-QING SHEN ◽  
WEN-YU SHAN ◽  
HAI-ZHOU LU
Keyword(s):  
Dirac Equation ◽  
Topological Insulator ◽  
Bound States ◽  
Topological Insulators ◽  
Mass Term ◽  
Point Of View ◽  
Quadratic Term ◽  
General Description ◽  
Dirac Equations ◽  
Topological Quantum

We present a general description of topological insulators from the point of view of Dirac equations. The Z2 index for the Dirac equation is always zero, and thus the Dirac equation is topologically trivial. After the quadratic term in momentum is introduced to correct the mass term m or the band gap of the Dirac equation, i.e., m → m − Bp2, the Z2 index is modified as 1 for mB > 0 and 0 for mB < 0. For a fixed B there exists a topological quantum phase transition from a topologically trivial system to a nontrivial system when the sign of mass m changes. A series of solutions near the boundary in the modified Dirac equation is obtained, which is characteristic of topological insulator. From the solutions of the bound states and the Z2 index we establish a relation between the Dirac equation and topological insulators.

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