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Primeur weekly 2018-08-13

Focus

DEEP-EST project is exploring the nuts and bolts of mildly disruptive modular supercomputing architecture ...

Gidel's FPGAs only use 1% of their capacity for lossless compression and encryption ...

German HPC and EuroHPC, a question of competitive collaboration benefiting science ...

Quantum computing

NSF launches effort to create practical quantum computer ...

The Rigetti 128-qubit chip and what it means for quantum ...

Quantum chains in graphene nanoribbons ...

Tying electrons down with nanoribbons ...

Focus on Europe

Falling moons: When proto-Earth met its makers - German and Israeli supercomputers spend 100 weeks crunching astronomical numbers ...

PRACE SHAPE Programme supports three further SMEs ...

High Performance Computing for a better agriculture ...

ExCAPE: developing new medicines with high performance computing ...

RDA Grants for Early Careers and Experts - Join the 12th RDA Plenary, 5-8 November 2018, Botswana as part of the International Data Week 2018 ...

Middleware

NetApp and NVIDIA supercharge deep learning with new AI architecture ...

Ohio Supercomputer Center hosting sixth meeting of the MVAPICH Users Group ...

Julia 1.0 has now been released ...

Hardware

Supermicro opens new era of petascale computing with a family of all-flash NVMe 1U systems scalable up to a petabyte of high performance storage ...

DDN building new flash enterprise virtualisation and analytics division with 100 new hires planned through September ...

Co-construction of the future university: Sugon signs with XJTLU ...

Intel launches world's densest, totally silent solid state drive ...

Intel's vision for the future of memory and storage with Optane + QLC ...

University of Texas at Arlington researcher working to use computer cache to speed up memory access ...

Applications

Blue Waters professor Kaiyu Guan receives AGU Early Career Award ...

NCSA Brown Dog project wins Best Technical Paper at PEARC18 ...

2018 NCSA Blue Waters Symposium presentations now available ...

Supercomputer simulations show new target in HIV-1 replication ...

Quantum chains in graphene nanoribbons


When graphene nanoribbons contain sections of varying width, robust new quantum states can be created in the transition zone.
9 Aug 2018 Dübendorf - Empa researchers, together with colleagues from the Max Planck Institute for Polymer Research in Mainz and other partners, have achieved a breakthrough that could in future be used for precise nanotransistors or - in the distant future - possibly even quantum computers, as the team reports in the current issue of the scientific journalNature.

A material that consists of atoms of a single element, but has completely different properties depending on the atomic arrangement - this may sound strange, but is actually reality with graphene nanoribbons. The ribbons, which are only a few carbon atoms wide and exactly one atom thick, have very different electronic properties depending on their shape and width: conductor, semiconductor or insulator. An international research team led by Empa's nanotech@surfaces laboratory has now succeeded in precisely adjusting the properties of the ribbons by specifically varying their shape. The particular feature of this technology is that not only can the "usual" electronic properties mentioned above be varied - it can also be used to generate specific local quantum states.

So what's behind it? If the width of a narrow graphene nanoribbon changes, in this case from seven to nine atoms, a special zone is created at the transition: because the electronic properties of the two areas differ in a special, so-called topological way, a "protected" and thus very robust new quantum state is created in the transition zone. This local electronic quantum state can now be used as a basic component to produce tailor-made semiconductors, metals or insulators - and possibly even as a component in quantum computers.

The Empa researchers under the lead of Oliver Gröning were able to show that if these ribbons are built with regularly alternating zones of different widths, a chain of interlinked quantum states with its own electronic structure is created by the numerous transitions. The exciting thing is that the electronic properties of the chain change depending on the width of the different segments. This allows them to be finely adjusted - from conductors to semiconductors with different bandgaps. This principle can be applied to many different types of transition zones - for instance, from seven to eleven atoms.

"The importance of this development is also underlined by the fact that a research group at the University of California, Berkeley, came to similar results independently of us", stated Oliver Gröning. The work of the US research team has been published alongside Oliver Gröning's in the same issue ofNature.

Based on these novel quantum chains, precise nano-transistors could be manufactured in the future - a fundamental step on the way to nanoelectronics. Whether the switching distance between the "1" state and the "0" state of the nanotransistor is actually large enough depends on the bandgap of the semiconductor - and with the new method this can be set almost at will.

In reality, however, this is not quite as simple: for the chain to have the desired electronic properties, each of the several hundred or even thousands of atoms must be in the right place. "This is based on complex, interdisciplinary research", stated Empa researcher Gröning. "Researchers from different disciplines in Dübendorf, Mainz, Dresden, and Troy (USA) worked together - from theoretical understanding and specific knowledge of how precursor molecules have to be built and how structures on surfaces can be selectively grown to structural and electronic analysis using a scanning tunneling microscope."

Ultrasmall transistors - and thus the next step in the further miniaturization of electronic circuits - are the obvious application possibilities here: although they are technically challenging, electronics based on nano-transistors actually work fundamentally the same as today's microelectronics. The semiconducting nanoribbons produced by the Empa researchers would allow transistors with a channel cross-section 1,000 times smaller than typically manufactured today. However, further possibilities can also be imagined, for example in the field of spintronics or even quantum informatics.

This is because the electronic quantum states at junctions of graphene nanoribbons of different widths can also carry a magnetic moment. This could make it possible to process information not by charge as was previously customary, but by the so-called spin - in the figurative sense the "direction of rotation" of the state. And the development could even go one step further. "We have observed that topological end states occur at the ends of certain quantum chains. This offers the possibility of using them as elements of so-called qubits - the complex, interlocked states in a quantum computer", explained Oliver Gröning.

Today and tomorrow, however, no quantum computer is built from nanoribbons - there is still a lot of research needed, said Oliver Gröning: "The possibility of flexibly adjusting the electronic properties through the targeted combination of individual quantum states represents a major leap for us in the production of new materials for ultra-miniaturized transistors." The fact that these materials are stable under environmental conditions plays an important role in the development of future applications.

"The further-reaching potential of the chains to create local quantum states and link them together in a targeted manner is also fascinating", Oliver Gröning continued. "Whether this potential can actually be exploited for future quantum computers remains to be seen, however. It is not enough to create localized topological states in the nanoribbons - these would also have to be coupled with other materials such as superconductors in such a way that the conditions for qubits are actually met."

The paper is titled "Engineering of robust topological quantum phases in graphene nanoribbons" .
Source: Swiss Federal Laboratories for Materials Science and Technology - EMPA

Back to Table of contents

Primeur weekly 2018-08-13

Focus

DEEP-EST project is exploring the nuts and bolts of mildly disruptive modular supercomputing architecture ...

Gidel's FPGAs only use 1% of their capacity for lossless compression and encryption ...

German HPC and EuroHPC, a question of competitive collaboration benefiting science ...

Quantum computing

NSF launches effort to create practical quantum computer ...

The Rigetti 128-qubit chip and what it means for quantum ...

Quantum chains in graphene nanoribbons ...

Tying electrons down with nanoribbons ...

Focus on Europe

Falling moons: When proto-Earth met its makers - German and Israeli supercomputers spend 100 weeks crunching astronomical numbers ...

PRACE SHAPE Programme supports three further SMEs ...

High Performance Computing for a better agriculture ...

ExCAPE: developing new medicines with high performance computing ...

RDA Grants for Early Careers and Experts - Join the 12th RDA Plenary, 5-8 November 2018, Botswana as part of the International Data Week 2018 ...

Middleware

NetApp and NVIDIA supercharge deep learning with new AI architecture ...

Ohio Supercomputer Center hosting sixth meeting of the MVAPICH Users Group ...

Julia 1.0 has now been released ...

Hardware

Supermicro opens new era of petascale computing with a family of all-flash NVMe 1U systems scalable up to a petabyte of high performance storage ...

DDN building new flash enterprise virtualisation and analytics division with 100 new hires planned through September ...

Co-construction of the future university: Sugon signs with XJTLU ...

Intel launches world's densest, totally silent solid state drive ...

Intel's vision for the future of memory and storage with Optane + QLC ...

University of Texas at Arlington researcher working to use computer cache to speed up memory access ...

Applications

Blue Waters professor Kaiyu Guan receives AGU Early Career Award ...

NCSA Brown Dog project wins Best Technical Paper at PEARC18 ...

2018 NCSA Blue Waters Symposium presentations now available ...

Supercomputer simulations show new target in HIV-1 replication ...