Topological superconductivity and Majorana fermions in metallic surface states

This article discusses recent developments relating to the so-called topological superconductors (TSCs), which have a full pairing gap in the bulk and gapless surface states consisting of Majorana fermions (MFs). It first provides a background on topological superconductivity as a novel quantum state of matter before turning to topological insulators (TIs) and superconducting heterostructures, with particular emphasis on the vortices of such materials and the Majorana mode within a vortex. It also considers proposals for realizing TSCs by proximity effects through TI/SC heterostructures as well as experimental efforts to fabricate artificial TSCs using nanowires, superconducting junctions, and ferromagnetic atomic chains on superconductors.

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Broken-symmetry states in topological insulators

Modern Physics Letters B ◽

10.1142/s0217984915300069 ◽

2015 ◽

Vol 29 (25) ◽

pp. 1530006

Author(s):

Yihua Wang

Keyword(s):

Three Dimensional ◽

Surface States ◽

Magnetic Monopoles ◽

Broken Symmetry ◽

Metallic Surface ◽

Photoemission Spectroscopy ◽

Majorana Fermions ◽

Magnetic Structures ◽

Light Pulses ◽

Fundamental Particles

Breaking the time-reversal symmetry (TRS) on the surface of a three-dimensional topological insulator (TI) transforms its metallic surface into a Chern insulator. The TRS-broken surface states are essential for many exotic emergent particles in condensed matter. In this review, I will show broken TRS surface states of TI induced by magnetism and by light imaged with scanning microscopy and photoemission spectroscopy, respectively. Our capability to manipulate mesoscopic magnetic structures as well as to shape ultrafast light pulses makes broken-symmetry states in TI promising platforms to simulate elusive fundamental particles such as magnetic monopoles and Majorana fermions.

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Half-metallic surface states and topological superconductivity in NaCoO2from first principles

Physical Review B ◽

10.1103/physrevb.84.060408 ◽

2011 ◽

Vol 84 (6) ◽

Cited By ~ 26

Author(s):

Hongming Weng ◽

Gang Xu ◽

Haijun Zhang ◽

Shou-Cheng Zhang ◽

Xi Dai ◽

...

Keyword(s):

First Principles ◽

Surface States ◽

Metallic Surface ◽

Half Metallic ◽

Topological Superconductivity

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A first-principles investigation of band inversion in topologically nontrivial Na2AgX (X= As, Sb and Bi) full Heusler compounds

Condensed Matter Physics ◽

10.5488/cmp.24.23602 ◽

2021 ◽

Vol 24 (2) ◽

pp. 23602

Author(s):

A. Boughena ◽

S. Benalia ◽

O. Cheref ◽

N. Bettahar ◽

D. Rached

Keyword(s):

First Principles ◽

Surface States ◽

Metallic Surface ◽

Full Potential ◽

Topological Order ◽

Heusler Compounds ◽

Spin Orbital ◽

Lmto Method ◽

Potential Applications ◽

Full Heusler

Topological nontrivial nature are the latest phases to be discovered in condensed matter physics with insulating bulk band gaps and topologically protected metallic surface states; they are one of the current hot topics because of their unique properties and potential applications. In this paper, we have highlighted a first-principles study of the structural stability and electronic behavior of the Na2AgX (X = As, Sb and Bi) full Heusler compounds, using the Full-Potential Linear Muffin-Tin Orbital (FP-LMTO) method. We have originated that the Hg2CuTi structure is appropriate in all studied materials. The negative values of the calculated formation energies mean that these compounds are energetically stable. The band structure is studied for the two cases relating the existence and the absence of spin-orbital couplings, where all materials are shown to be topologically non-trivial compounds. Spin orbital couplings were noticed to have no significant effect on the electronic properties such as the topological order.

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Minority metallic surface states of a half-metallic ferrimagnet

Surface Science ◽

10.1016/s0039-6028(01)01547-3 ◽

2001 ◽

Vol 494 (3) ◽

pp. L793-L798 ◽

Cited By ~ 47

Author(s):

S.J Jenkins ◽

D.A King

Keyword(s):

Surface States ◽

Metallic Surface ◽

Half Metallic

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Studies on the origin of the interfacial superconductivity of Sb2Te3/Fe1+yTe heterostructures

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1914534117 ◽

2019 ◽

Vol 117 (1) ◽

pp. 221-227 ◽

Cited By ~ 1

Author(s):

Jing Liang ◽

Yu Jun Zhang ◽

Xiong Yao ◽

Hui Li ◽

Zi-Xiang Li ◽

...

Keyword(s):

Layer Thickness ◽

Topological Insulator ◽

Surface States ◽

The Other ◽

Majorana Fermions ◽

Bulk Conductivity ◽

Indirect Coupling ◽

Topological Surface ◽

Excess Fe

The recent discovery of the interfacial superconductivity (SC) of the Bi2Te3/Fe1+yTe heterostructure has attracted extensive studies due to its potential as a novel platform for trapping and controlling Majorana fermions. Here we present studies of another topological insulator (TI)/Fe1+yTe heterostructure, Sb2Te3/Fe1+yTe, which also has an interfacial 2-dimensional SC. The results of transport measurements support that reduction of the excess Fe concentration of the Fe1+yTe layer not only increases the fluctuation of its antiferromagnetic (AFM) order but also enhances the quality of the SC of this heterostructure system. On the other hand, the interfacial SC of this heterostructure was found to have a wider-ranging TI-layer thickness dependence than that of the Bi2Te3/Fe1+yTe heterostructure, which is believed to be attributed to the much higher bulk conductivity of Sb2Te3that enhances indirect coupling between its top and bottom topological surface states (TSSs). Our results provide evidence of the interplay among the AFM order, itinerant carries from the TSSs, and the induced interfacial SC of the TI/Fe1+yTe heterostructure system.

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Evidence for absence of metallic surface states in BiO2-terminated BaBiO3 thin films

Current Applied Physics ◽

10.1016/j.cap.2018.03.015 ◽

2018 ◽

Vol 18 (6) ◽

pp. 658-662 ◽

Cited By ~ 1

Author(s):

Ji Seop Oh ◽

Minu Kim ◽

Gideok Kim ◽

Han Gyeol Lee ◽

Hyang Keun Yoo ◽

...

Keyword(s):

Thin Films ◽

Surface States ◽

Metallic Surface

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Observation of Two Dimensional Metallic Surface States and Metal to Semiconductor Transition on Low Dimensional Polar Thin Films

ECS Meeting Abstracts ◽

10.1149/ma2016-01/26/1333 ◽

2016 ◽

Keyword(s):

Thin Films ◽

Surface States ◽

Metallic Surface ◽

Two Dimensional ◽

Low Dimensional

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Sodium Doping of Bi/Si(111) Ultra-Thin Films

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.213.65 ◽

2014 ◽

Vol 213 ◽

pp. 65-70

Author(s):

Maria V. Ryzhkova ◽

Dimitry V. Gruznev ◽

Elena A. Borisenko ◽

Dmitry A. Tsukanov

Keyword(s):

Thin Films ◽

Electrical Conductance ◽

Surface States ◽

Surface Conductivity ◽

Metallic Surface ◽

Photoemission Spectroscopy ◽

Angle Resolved Photoemission Spectroscopy ◽

Sodium Doping ◽

Reconstructed Surfaces ◽

Conductance Changes

Changes in electrical conductance of the Bi/Si (111) reconstructed surfaces and Bi {012} or Bi (001) ultra-thin films have been studied after sodium deposition at room temperature. It was observed that deposition of sodium onto Si (111)-β-3×3-Bi surface results in increasing of surface conductivity up to 0.3 monolayers (ML) of adsorbed sodium atoms. These conductance changes were explained by developing of the metallic surface states in the band gap as revealed by angle resolved photoemission spectroscopy spectra. Moreover, it was shown that sodium adsorption onto Bi {012} and Bi (001) thin films leads to drastic changes in its surface conductivity including a peak of maximum electrical conductance at 0.5 monolayers of adsorbed sodium.

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