Resistively detected NMR as a probe of the topological nature of conducting edge/surface states

Abstract Since the theoretical prediction and experimental observation of the magnon thermal Hall effect, a variety of novel phenomena that may occur in magnonic systems have been proposed. We review recent advances in the study of topological phases of magnon Bogoliubov–de Gennes (BdG) systems. After giving an overview of previous works on electronic topological insulators and the magnon thermal Hall effect, we provide the necessary background for bosonic BdG systems, with particular emphasis on their non-Hermiticity arising from the diagonalization of the BdG Hamiltonian. We then introduce definitions of $$ \mathbb{Z}_2 $$ topological invariants for bosonic systems with pseudo-time-reversal symmetry, which ensures the existence of bosonic counterparts of “Kramers pairs.” Because of the intrinsic non-Hermiticity of bosonic BdG systems, these topological invariants have to be defined in terms of the bosonic Berry connection and curvature. We then introduce theoretical models that can be thought of as magnonic analogs of two- and three-dimensional topological insulators in class AII. We demonstrate analytically and numerically that the $$ \mathbb{Z}_2 $$ topological invariants precisely characterize the presence of gapless edge/surface states. We also predict that bilayer CrI$$_3$$ with a particular stacking would be an ideal candidate for the realization of a two-dimensional magnon system characterized by a nontrivial $$ \mathbb{Z}_2 $$ topological invariant. For three-dimensional topological magnon systems, the magnon thermal Hall effect is expected to occur when a magnetic field is applied to the surface.

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Influence of the near‐band‐edge surface states on the luminescence efficiency of InP

Applied Physics Letters ◽

10.1063/1.96910 ◽

1986 ◽

Vol 48 (20) ◽

pp. 1362-1364 ◽

Cited By ~ 31

Author(s):

J. M. Moison ◽

M. Van Rompay ◽

M. Bensoussan

Keyword(s):

Surface States ◽

Band Edge ◽

Near Band Edge ◽

Luminescence Efficiency ◽

Edge Surface

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Intrinsically core-shell plasmonic dielectric nanostructures with ultrahigh refractive index

Science Advances ◽

10.1126/sciadv.1501536 ◽

2016 ◽

Vol 2 (3) ◽

pp. e1501536 ◽

Cited By ~ 50

Author(s):

Zengji Yue ◽

Boyuan Cai ◽

Lan Wang ◽

Xiaolin Wang ◽

Min Gu

Keyword(s):

Refractive Index ◽

High Performance ◽

Topological Insulators ◽

Near Infrared ◽

Surface States ◽

Core Shell ◽

Frequency Range ◽

Plasmonic Nanostructure ◽

Edge Surface ◽

Infrared Frequency Range

Topological insulators are a new class of quantum materials with metallic (edge) surface states and insulating bulk states. They demonstrate a variety of novel electronic and optical properties, which make them highly promising electronic, spintronic, and optoelectronic materials. We report on a novel conic plasmonic nanostructure that is made of bulk-insulating topological insulators and has an intrinsic core-shell formation. The insulating (dielectric) core of the nanocone displays an ultrahigh refractive index of up to 5.5 in the near-infrared frequency range. On the metallic shell, plasmonic response and strong backward light scattering were observed in the visible frequency range. Through integrating the nanocone arrays into a-Si thin film solar cells, up to 15% enhancement of light absorption was predicted in the ultraviolet and visible ranges. With these unique features, the intrinsically core-shell plasmonic nanostructure paves a new way for designing low-loss and high-performance visible to infrared optical devices.

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Near-field Strong Plasmonic Resonances in Bi1.5Sb0.5Te1.8Se1.2 Topological Insulator Film

10.21203/rs.3.rs-1035749/v1 ◽

2021 ◽

Author(s):

Baoshan Guo ◽

Huan Yao ◽

Ningwei Zhan ◽

Lan Jiang

Keyword(s):

Topological Insulator ◽

Electromagnetic Waves ◽

Near Infrared ◽

Near Field ◽

Surface States ◽

Field Energy ◽

Hole Array ◽

Infrared Range ◽

Plasmonic Material ◽

Edge Surface

Abstract Topological insulators are a new class of quantum materials with metallic (edge) surface states and insulating bulk states. They exhibit various novel electronic and optical properties that make them highly promising electronic, spintronic, and optoelectronic materials. Our report confirms that the topological insulator Bi 1.5 Sb 0.5 Te 1.8 Se 1.2 (BSTS) is also an effective plasmonic material in the visible and near-infrared range. A BSTS film can effectively control transmission and reflection characteristics by changing the period of the hole array. This study determined that a strong resonant surface plasmonic mode at the resonance peak can confine approximately 80% of the electromagnetic field energy is demonstrated. Higher-order (second- and third-order) resonance peaks were also found, which is critical for controlling electromagnetic waves and research into new optoelectronic devices.

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Quantum spin Hall effect and topological insulators

10.1093/oso/9780198787075.003.0017 ◽

2017 ◽

Author(s):

S. Murakami ◽

T. Yokoyama

Keyword(s):

Topological Insulators ◽

Surface States ◽

Two Dimensions ◽

Quantum Spin ◽

Three Dimensions ◽

Pure Spin ◽

Topological Order ◽

Edge States ◽

Edge Surface ◽

Quantum Spin Hall

This chapter begins with a description of quantum spin Hall systems, or topological insulators, which embody a new quantum state of matter theoretically proposed in 2005 and experimentally observed later on using various methods. Topological insulators can be realized in both two dimensions (2D) and in three dimensions (3D), and are nonmagnetic insulators in the bulk that possess gapless edge states (2D) or surface states (3D). These edge/surface states carry pure spin current and are sometimes called helical. The novel property for these edge/surface states is that they originate from bulk topological order, and are robust against nonmagnetic disorder. The following sections then explain how topological insulators are related to other spin-transport phenomena.

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Tight-binding approximation for bulk and edge electronic states in graphene

Canadian Journal of Physics ◽

10.1139/cjp-2014-0313 ◽

2015 ◽

Vol 93 (5) ◽

pp. 580-584 ◽

Cited By ~ 2

Author(s):

Oana-Ancuta Dobrescu ◽

M. Apostol

Keyword(s):

Finite Differences ◽

Tight Binding ◽

Electronic States ◽

Surface States ◽

Graphene Sheets ◽

Graphene Monolayer ◽

Edge States ◽

Tight Binding Approximation ◽

Edge Elements ◽

Edge Surface

The tight-binding approximation is employed here to investigate electronic bulk and edge (“surface”) states in semi-infinite graphene sheets and graphene monolayer ribbons with various edge terminations (zigzag, horseshoe, and armchair edges). It is shown that edge states do not exist for a uniform hopping (transfer) matrix. The problem is generalized to include edge elements of the hopping matrix distinct from the infinite-sheet (“bulk”) ones. In this case, semi-infinite graphene sheets with zigzag or horseshoe edges exhibit edge states, while semi-infinite graphene sheets with armchair edges do not. The energy of the edge states lies above the (zero) Fermi level. Similarly, symmetric graphene ribbons with zigzag or horseshoe edges exhibit edge states, while ribbons with asymmetric edges (zigzag and horseshoe) do not. It is also shown how to construct the “reflected” solutions (bulk states) for the intervening equations with finite differences both for semi-infinite sheets and ribbons.

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Zero-loss omega-filtered REM and RHEED on the new Zeiss 912

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087392 ◽

1991 ◽

Vol 49 ◽

pp. 616-617

Author(s):

J.C.H. Spence ◽

J. Mayer

Keyword(s):

Electron Microscopy ◽

Materials Science ◽

Surface States ◽

Ccd Camera ◽

Dark Field ◽

Ion Pump ◽

Magnetic Imaging ◽

Reflection Electron Microscopy ◽

Diffraction Patterns ◽

Large Background

The Zeiss 912 is a new fully digital, side-entry, 120 Kv TEM/STEM instrument for materials science, fitted with an omega magnetic imaging energy filter. Pumping is by turbopump and ion pump. The magnetic imaging filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient parallel (area) detection. The energy loss intensity distribution may also be displayed on the screen, and recorded by scanning it over the PMT supplied. If a CCD camera is fitted and suitable new software developed, “parallel ELS” recording results. For large fields of view, filtered images can be recorded much more efficiently than by Scanning Reflection Electron Microscopy, and the large background of inelastic scattering removed. We have therefore evaluated the 912 for REM and RHEED applications. Causes of streaking and resonance in RHEED patterns are being studied, and a more quantitative analysis of CBRED patterns may be possible. Dark field band-gap REM imaging of surface states may also be possible.

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