Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Interdisciplinary team demonstrates superconducting qualities of topological insulators

11.04.2013
Findings may prove useful in search for elusive Majorana quasiparticle
Topological insulators (TIs) are an exciting new type of material that on their surface carry electric current, but within their bulk, act as insulators. Since the discovery of TIs about a decade ago, their unique characteristics (which point to potential applications in quantum computing) have been explored theoretically, and in the last five years, experimentally.

But where in theory, the bulk of TIs carry no current, in the laboratory, impurities and disorder in real materials mean that the bulk is, in fact, conductive. This has proven an obstacle to experimentation with TIs: findings from prior experiments designed to test the surface conductivity of TIs unavoidably included contributions from the surplus of electrons in the bulk.

Now an interdisciplinary research team at the University of Illinois at Urbana-Champaign, in collaboration with researchers at Brookhaven National Laboratory’s Condensed Matter Physics and Materials Science Department, has measured superconductive surface states in TIs where the bulk charge carriers were successfully depleted. The research paper, "Symmetry protected Josephson supercurrents in three-dimensional topological insulators," was published this week in Nature Communications.

The experiments, conducted in the laboratory of Illinois condensed matter physicist Nadya Mason at the Frederick Seitz Materials Research Laboratory, were carried out by postdoctoral research associate Sungjae Cho using TI material—specially developed by the Brookhaven team—coupled to superconducting leads.

To deplete the electrons in the bulk, the team used three strategies: the TI material was doped with antimony, then it was doped at the surface with a chemical with strong electron affinity, and finally an electrostatic gate was used to apply voltage that lowered the energy of the entire system.

“One of the main results we found,” said Mason, “was in comparing the two experimental regimes, pure surface (bulk depleted of electrons) vs. bulk (excess electrons present in impurities in bulk material). We learned that even when you have the bulk, the superconductivity always goes through the surface of the material.”

This finding was established by comparing experiments with theoretical modeling by research team members at Illinois’s Department of Electrical and Computer Engineering—Assistant Professor Matthew Gilbert and graduate student Brian Dellabetta—which showed that superconductivity occured only at the surface of topological insulators and that this is a unique characteristic of these new materials.

It’s been predicted that TIs harbor the highly sought Majorana quasiparticle, a fermion which is theorized to be its own antiparticle and which if discovered, could serve as a quantum bit in quantum computing.

“Since we now have a better understanding of how topological insulators behave with regard to superconductivity, this will assist our search for the Majorana quasiparticle,” Mason explained.

The team also plans to investigate the same experimental configuration at lower energy to further explore its characteristics.

“The potential of this new material is very exciting. We are exploring possible uses for TIs in terms of conventional electronic devices and novel devices,” said Mason. “And if we can find the new particle predicted to exist in the material’s solid state, and then learn to manipulate its position relative to a second particle, we could use it for quantum computation.

“The implications for quantum computing are truly profound,” she explained. “With today’s technology, computer components really can’t get much smaller. If Majoranas behave as predicted and can be manipulated to serve as quantum bits, our future computers would be extraordinarily powerful; their components would be much smaller and would be able to store much more information.”

This research was funded by a grant from the Office of Naval Research under grant N0014-11-1-0728.
Contact: Nadya Mason, Department of Physics, 217/244-9114
Writer: Siv Schwink, Department of Physics, 217/552-5671

Nadya Mason | University of Illinois
Further information:
http://www.illinois.edu

More articles from Interdisciplinary Research:

nachricht A new method for the 3-D printing of living tissues
16.08.2017 | University of Oxford

nachricht Bergamotene - alluring and lethal for Manduca sexta
21.04.2017 | Max-Planck-Institut für chemische Ökologie

All articles from Interdisciplinary Research >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The fastest light-driven current source

Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.

Graphene is up to the job

Im Focus: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Nerves control the body’s bacterial community

26.09.2017 | Life Sciences

Four elements make 2-D optical platform

26.09.2017 | Physics and Astronomy

Goodbye, login. Hello, heart scan

26.09.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>