scholarly journals Manipulating topology in tailored artificial graphene nanoribbons

2021 ◽  
Author(s):  
Nathan Guisinger ◽  
Daniel Trainer ◽  
Srilok Sriniva ◽  
Brandon Fisher ◽  
Yuan Zhang ◽  
...  
Keyword(s):  
Graphene Nanoribbons ◽  
Research Effort ◽  
Copper Surface ◽  
Quantum States ◽  
Topological Phases ◽  
Spintronic Devices ◽  
Graphene Derivatives ◽  
Topological States ◽  
Exotic Physics ◽  
Artificial Graphene

Abstract Topological phases of matter give rise to exotic physics that can be leveraged for next generation quantum computation1–3 and spintronic devices4,5. Thus, the search for topological phases and the quantum states that they exhibit have become the subject of a massive research effort in condensed matter physics. Topologically protected states have been produced in a variety of systems, including artificial lattices6–9, graphene nanoribbons (GNRs)10,11 and bismuth bilayers12,13. Despite these advances, the real-time manipulation of individual topological states and their relative coupling, a necessary feature for the realization of topological qubits, remains elusive. Guided by first-principles calculations, we spatially manipulate robust, zero-dimensional topological states by altering the topological invariants of quasi-one-dimensional artificial graphene nanostructures. This is achieved by positioning carbon monoxide molecules on a copper surface to confine its surface state electrons into artificial atoms positioned to emulate the low-energy electronic structure of graphene derivatives. Ultimately, we demonstrate control over the coupling between adjacent topological states that are finely engineered and simulate complex Hamiltonians. Our atomic synthesis gives access to an infinite range of nanoribbon geometries, including those beyond the current reach of synthetic chemistry, and thus provides an ideal platform for the design and study of novel topological and quantum states of matter.

scholarly journals Strain driven emergence of topological non-triviality in YPdBi thin films

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Vishal Bhardwaj ◽  
Anupam Bhattacharya ◽  
Shivangi Srivastava ◽  
Vladimir V. Khovaylo ◽  
Jhuma Sannigrahi ◽  
...  
Keyword(s):  
Thin Films ◽  
Heavy Fermion ◽  
Critical Role ◽  
Surface States ◽  
Strain Engineering ◽  
Emergent Properties ◽  
Spintronic Devices ◽  
Topological States ◽  
Topological Surface ◽  
Strained Films

AbstractHalf-Heusler compounds exhibit a remarkable variety of emergent properties such as heavy-fermion behaviour, unconventional superconductivity and magnetism. Several of these compounds have been predicted to host topologically non-trivial electronic structures. Remarkably, recent theoretical studies have indicated the possibility to induce non-trivial topological surface states in an otherwise trivial half-Heusler system by strain engineering. Here, using magneto-transport measurements and first principles DFT-based simulations, we demonstrate topological surface states on strained [110] oriented thin films of YPdBi grown on (100) MgO. These topological surface states arise in an otherwise trivial semi-metal purely driven by strain. Furthermore, we observe the onset of superconductivity in these strained films highlighting the possibility of engineering a topological superconducting state. Our results demonstrate the critical role played by strain in engineering novel topological states in thin film systems for developing next-generation spintronic devices.

scholarly journals Electrically tunable low-density superconductivity in a monolayer topological insulator

Science ◽  
2018 ◽  
Vol 362 (6417) ◽  
pp. 926-929 ◽  
Author(s):  
Valla Fatemi ◽  
Sanfeng Wu ◽  
Yuan Cao ◽  
Landry Bretheau ◽  
Quinn D. Gibson ◽  
...  
Keyword(s):  
Ground State ◽  
Field Effect ◽  
Field Effect Transistor ◽  
Quantum Spin ◽  
Topological Phases ◽  
Critical Temperatures ◽  
Topological States ◽  
Effect Transistor ◽  
Topological Phases Of Matter

Turning on superconductivity in a topologically nontrivial insulator may provide a route to search for non-Abelian topological states. However, existing demonstrations of superconductor-insulator switches have involved only topologically trivial systems. Here we report reversible, in situ electrostatic on-off switching of superconductivity in the recently established quantum spin Hall insulator monolayer tungsten ditelluride (WTe2). Fabricated into a van der Waals field-effect transistor, the monolayer’s ground state can be continuously gate-tuned from the topological insulating to the superconducting state, with critical temperaturesTcup to ~1 kelvin. Our results establish monolayer WTe2as a material platform for engineering nanodevices that combine superconducting and topological phases of matter.

Electronic spectra, topological states, and impurity effects in graphene nanoribbons

2021 ◽  
Vol 47 (9) ◽  
pp. 754-764
Author(s):  
Yu. G. Pogorelov ◽  
D. Kochan ◽  
V. M. Loktev
Keyword(s):  
Electronic Spectra ◽  
Graphene Nanoribbons ◽  
Impurity Effects ◽  
Topological States

Spin-filtering and tunneling magnetoresistance effects in 6,6,12-graphyne-based molecular magnetic tunnel junctions

2019 ◽  
Vol 21 (5) ◽  
pp. 2734-2742 ◽  
Author(s):  
Jin Li ◽  
Maoyun Di ◽  
Zhi Yang ◽  
Li-Chun Xu ◽  
Yongzhen Yang ◽  
...  
Keyword(s):  
Tunnel Junctions ◽  
Graphene Nanoribbons ◽  
Magnetic Tunnel Junctions ◽  
Tunneling Magnetoresistance ◽  
Spintronic Devices ◽  
Zigzag Graphene Nanoribbons ◽  
Spin Filtering

By designing two kinds of molecular magnetic tunnel junctions based on 6,6,12-graphyne and zigzag graphene nanoribbons, the spin-filtering and tunneling magnetoresistance effects of spintronic devices can be dramatically enhanced.

scholarly journals Multipolar lasing modes from topological corner states

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Ha-Reem Kim ◽  
Min-Soo Hwang ◽  
Daria Smirnova ◽  
Kwang-Yong Jeong ◽  
Yuri Kivshar ◽  
...  
Keyword(s):  
Domain Walls ◽  
Optical Gain ◽  
Topological Phases ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Finite Systems ◽  
Large Size ◽  
Topological States ◽  
Lasing Modes ◽  
Directional Transport

AbstractTopological photonics provides a fundamental framework for robust manipulation of light, including directional transport and localization with built-in immunity to disorder. Combined with an optical gain, active topological cavities hold special promise for a design of light-emitting devices. Most studies to date have focused on lasing at topological edges of finite systems or domain walls. Recently discovered higher-order topological phases enable strong high-quality confinement of light at the corners. Here, we demonstrate lasing action of corner states in nanophotonic topological structures. We identify several multipole corner modes with distinct emission profiles via hyperspectral imaging and discern signatures of non-Hermitian radiative coupling of leaky topological states. In addition, depending on the pump position in a large-size cavity, we generate selectively lasing from either edge or corner states within the topological bandgap. Our studies provide the direct observation of multipolar lasing and engineered collective resonances in active topological nanostructures.

scholarly journals The family of topological phases in condensed matter†

2013 ◽  
Vol 1 (1) ◽  
pp. 49-59 ◽  
Author(s):  
Shun-Qing Shen
Keyword(s):  
Topological Insulators ◽  
Condensed Matter ◽  
Quantum States ◽  
Condensed Matter Physics ◽  
Topological Phases ◽  
Important Advance ◽  
Global Properties ◽  
The Family ◽  
Boundary States ◽  
Historic Development

Abstract The discovery of topological insulators and superconductors is an important advance in condensed matter physics. Topological phases reflect global properties of the quantum states in materials, and the boundary states are the characteristic of the materials. Such phases constitute a new branch in condensed matter physics. Here a historic development is briefly introduced, and the known family of phases in condensed matter are summarized.

scholarly journals Voltage-dependent spin flip in magnetically substituted graphene nanoribbons: Towards the realization of graphene-based spintronic devices

2017 ◽  
Vol 95 (15) ◽  
Author(s):  
Gregory Houchins ◽  
Charles B. Crook ◽  
Jian-Xin Zhu ◽  
Alexander V. Balatsky ◽  
Jason T. Haraldsen
Keyword(s):  
Graphene Nanoribbons ◽  
Spintronic Devices ◽  
Spin Flip ◽  
Voltage Dependent

scholarly journals In situ growth of large-area and self-aligned graphene nanoribbon arrays on liquid metal

2020 ◽  
Author(s):  
Le Cai ◽  
Wanzhen He ◽  
Xudong Xue ◽  
Jianyao Huang ◽  
Ke Zhou ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Graphene Nanoribbons ◽  
Chemical Vapour ◽  
Copper Surface ◽  
In Situ Growth ◽  
Large Area ◽  
High Quality ◽  
Hydrogen Flow ◽  
Template Free

Abstract Intrinsic graphene features semi-metallic characteristics that limit its applications in electronic devices, whereas graphene nanoribbons (GNRs) are promising semiconductors owing to their bandgap-opening feature. However, the controllable mass-fabrication of high-quality GNR arrays remains a major challenge. In particular, the in situ growth of GNR arrays through template-free chemical vapour deposition (CVD) has not been realized. Herein, we report a template-free CVD strategy to grow large-area, high-quality, and self-aligned GNR arrays on the liquid copper surface. The width of as-grown GNR could be optimized to sub-10 nm with aspect ratio up to 387, which is higher than those of reported CVD-GNRs. The study of the growth mechanism indicates that a unique comb-like etching-regulated growth process caused by a trace hydrogen flow guides the formation of the mass-produced self-aligned GNR arrays. Our approach is operationally simple and efficient, offering an assurance for the use of GNR arrays in integrated circuits.

Introduction

2021 ◽  
pp. 3-30
Author(s):  
Gang Cao ◽  
Lance E. DeLong
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Quantum States ◽  
Spin Orbit ◽  
Crystalline Electric Field ◽  
Topological States ◽  
Coulomb Correlations ◽  
Relationship Of ◽  
The Relationship

The fundamental and technological importance of transition metal oxides, and the relationship of the present work to previous monographs dealing with transition metal oxides are reviewed. The relatively abundant 3d-transition metal oxides are contrasted with the rarer 4d- and 5d-transition metal oxides that exhibit a unique interplay between spin-orbit, exchange, crystalline electric field and Coulomb correlations. The combined effect of these fundamental interactions yields peculiar quantum states and empirical trends that markedly differ from those of their 3d counterparts. General trends in the electronic structure are related to generalized phase diagrams of the magnetic and insulating ground states. The intriguing absence of experimental evidence for predicted topological states and superconductivity in these materials are discussed.

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