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Primeur weekly 2019-07-22

Focus

EuroHPC Research and Innovation calls open July 25 with a total budget of 95 million euro ...

Quantum computing

Limitation exposed in promising quantum computing material ...

Bristol awarded GBP 8,4 million to strengthen quantum research programmes ...

Researchers build transistor-like gate for quantum information processing - with qudits ...

Fujitsu harnesses Quantum-inspired Digital Annealer technology to optimize output efficiency in power generation for renewable energy devices ...

Quantum photonics by serendipity ...

Focus on Europe

Hungary joins Italian pre-exascale EuroHPC consortium ...

Middleware

SUSE joins the iRODS Consortium ...

Hardware

NSF awards $10 million to SDSC to deploy 'Expanse' supercomputer ...

GRC announces licensing agreement with Nihon Form Services to tailor GRC's data centre immersion cooling technology for the Japanese market ...

High Performance Computing (HPC) arrives at the Edge of Space ...

Arm Flexible Access gives chip designers the freedom to experiment and test before they invest ...

Supermicro brings unprecedented performance and configurability to the intelligent edge for new security, 5G, and AI solutions ...

SwiftStack joins NVIDIA Partner Network ...

Intel and SAP broaden their technology partnership to power enterprises' digital transformation ...

The Pittsburgh Supercomputing Center to host Bridges-2 supercomputers at Next Tier Connect ...

Applications

HPC4Energy Innovation Programme announces first awards for public/private partnerships ...

Atos orchestrates AURAGEN's genomic sequencing calculation solution ...

Who's using Argonne's user facilities? ...

Predicting material properties with quantum Monte Carlo ...

NERSC hosts first 'GPUs for Science' Workshop ...

First Corones Award goes to NERSC computer scientist ...

HPC4Manufacturing project aims at improving thin-film processes used in LED lights ...

Dirty bomb simulator prepares responders ...

LHC experiments present new results on rare Higgs phenomena at 2019 EPS-HEP conference ...

RIT professor honoured with Presidential Early Career Award for Scientists and Engineers ...

A graphene superconductor that plays more than one tune ...

The Cloud

Atos becomes a Microsoft Azure Expert Managed Service Provider (MSP) ...

Limitation exposed in promising quantum computing material


Vikram Deshpande, assistant professor in the Department of Physics & Astronomy (left) and doctoral candidate Su Kong Chong (right) stand in the "coolest lab on campus". Deshpande leads a lab that can cool topological materials down to just a few fractions of a degree above absolute zero at -273.15°C (-459.67°F). It is literally the coldest laboratory on campus. Credit: Lisa Potter/University of Utah.
16 Jul 2019 Salt Lake City - Quantum computers promise to perform operations of great importance believed to be impossible for our technology today. Current computers process information via transistors carrying one of two units of information, either a 1 or a 0. Quantum computing is based on the quantum mechanical behaviour of the logic unit. Each quantum unit, or "qubit", can exist in a quantum superposition rather than taking discrete values. The biggest hurdles to quantum computing are the qubits themselves - it is an ongoing scientific challenge to create logic units robust enough to carry instructions without being impacted by the surrounding environment and resulting errors.

Physicists have theorized that a new type of material, called a three-dimensional (3D) topological insulator (TI), could be a good candidate from which to create qubits that will be resilient from these errors and protected from losing their quantum information. This material has both an insulating interior and metallic top and bottom surfaces that conduct electricity. The most important property of 3D topological insulators is that the conductive surfaces are predicted to be protected from the influence of the surroundings. Few studies exist that have experimentally tested how TIs behave in real life.

A new study from the University of Utah found that in fact, when the insulating layers are as thin as 16 quintuple atomic layers across, the top and bottom metallic surfaces begin to influence each other and destroy their metallic properties. The experiment demonstrates that the opposite surfaces begin influencing each other at a much thicker insulating interior than previous studies had shown, possibly approaching a rare theoretical phenomenon in which the metallic surfaces also become insulating as the interior thins out.

"Topological insulators could be an important material in future quantum computing. Our findings have uncovered a new limitation in this system", stated Vikram Deshpande, assistant professor of physics at the University of Utah and corresponding author of the study. "People working with topological insulators need to know what their limits are. It turns out that as you approach that limit, when these surfaces start 'talking' to each other, new physics shows up, which is also pretty cool by itself."

The new study published on July 16, 2019 in the journal Physics Review Letters .

Imagine a hardcover textbook as a 3D topological insulator, Vikram Deshpande said. The bulk of the book are the pages, which is an insulator layer - it can't conduct electricity. The hardcovers themselves represent the metallic surfaces. Ten years ago, physicists discovered that these surfaces could conduct electricity, and a new topological field was born.

Vikram Deshpande and his team created devices using 3D TIs by stacking five few-atom-thin layers of various materials into sloppy sandwich-like structures. The bulk core of the sandwich is the topological insulator, made from a few quintuple layers of bismuth antimony tellurium selenide (Bi2-xSbxTe3-ySey). This core is sandwiched by a few layers of boron nitride, and is topped off with two layers of graphite, above and below. The graphite works like metallic gates, essentially creating two transistors that control conductivity. Last year Vikram Deshpande led a study that showed that this topological recipe built a device that behaved like you would expect - bulk insulators that protect the metallic surfaces from the surrounding environment.

In this study, they manipulated the 3D TI devices to see how the properties changed. First, they built van der Waal heterostructures - those sloppy sandwiches - and exposed them to a magnetic field. Vikram Deshpande's team tested many at his lab at the University of Utah and first author Su Kong Chong, doctoral candidate at the U, traveled to the National High Magnetic Field Lab in Tallahassee to perform the same experiments there using one of the highest magnetic fields in the country. In the presence of the magnetic field, a checkerboard pattern emerged from the metallic surfaces, showing the pathways by which electrical current will move on the surface. The checkerboards, consisting of quantized conductivities versus voltages on the two gates, are well-defined, with the grid intersecting at neat intersection points, allowing the researchers to track any distortion on the surface.

They began with the insulator layer at 100 nanometers thick, about a thousandth of the diameter of a human hair, and progressively got thinner down to 10 nanometers. The pattern started distorting until the insulator layer was at 16 nanometers thick, when the intersection points began to break up, creating a gap that indicated that the surfaces were no longer conductive.

"Essentially, we've made something that was metallic into something insulating in that parameter space. The point of this experiment is that we can controllably change the interaction between these surfaces", stated Vikram Deshpande. "We start out with them being completely independent and metallic, and then start getting them closer and closer until they start 'talking', and when they're really close, they are essentially gapped out and become insulating."

Previous experiments in 2010 and 2012 had also observed the energy gap on the metallic surfaces as the insulating material thins out. But those studies concluded that the energy gap appeared with much thinner insulating layers - five nanometers in size. This study observed the metallic surface properties break down at much larger interior thickness, up to 16 nanometers. The other experiments used different "surface science" methods where they observed the materials through a microscope with a very sharp metallic tip to look at every atom individually or studied them with highly energetic light.

"These were extremely involved experiments which are pretty far removed from the device-creation that we are doing", stated Vikram Deshpande.

Next, Vikram Deshpande and the team will look more closely into the physics creating that energy gap on the surfaces. He predicts that these gaps can be positive or negative depending on material thickness.

Other authors who contributed to the study are Kyu Bum Han and Taylor Sparks from the University's Department of Materials Science and Engineering.
Source: University of Utah

Back to Table of contents

Primeur weekly 2019-07-22

Focus

EuroHPC Research and Innovation calls open July 25 with a total budget of 95 million euro ...

Quantum computing

Limitation exposed in promising quantum computing material ...

Bristol awarded GBP 8,4 million to strengthen quantum research programmes ...

Researchers build transistor-like gate for quantum information processing - with qudits ...

Fujitsu harnesses Quantum-inspired Digital Annealer technology to optimize output efficiency in power generation for renewable energy devices ...

Quantum photonics by serendipity ...

Focus on Europe

Hungary joins Italian pre-exascale EuroHPC consortium ...

Middleware

SUSE joins the iRODS Consortium ...

Hardware

NSF awards $10 million to SDSC to deploy 'Expanse' supercomputer ...

GRC announces licensing agreement with Nihon Form Services to tailor GRC's data centre immersion cooling technology for the Japanese market ...

High Performance Computing (HPC) arrives at the Edge of Space ...

Arm Flexible Access gives chip designers the freedom to experiment and test before they invest ...

Supermicro brings unprecedented performance and configurability to the intelligent edge for new security, 5G, and AI solutions ...

SwiftStack joins NVIDIA Partner Network ...

Intel and SAP broaden their technology partnership to power enterprises' digital transformation ...

The Pittsburgh Supercomputing Center to host Bridges-2 supercomputers at Next Tier Connect ...

Applications

HPC4Energy Innovation Programme announces first awards for public/private partnerships ...

Atos orchestrates AURAGEN's genomic sequencing calculation solution ...

Who's using Argonne's user facilities? ...

Predicting material properties with quantum Monte Carlo ...

NERSC hosts first 'GPUs for Science' Workshop ...

First Corones Award goes to NERSC computer scientist ...

HPC4Manufacturing project aims at improving thin-film processes used in LED lights ...

Dirty bomb simulator prepares responders ...

LHC experiments present new results on rare Higgs phenomena at 2019 EPS-HEP conference ...

RIT professor honoured with Presidential Early Career Award for Scientists and Engineers ...

A graphene superconductor that plays more than one tune ...

The Cloud

Atos becomes a Microsoft Azure Expert Managed Service Provider (MSP) ...