Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A 'nanoscale landscape' controls flow of surface electrons on a topological insulator

26.10.2012
Stripe-like contours on a surface modulate electrons that behave like light

In the relatively new scientific frontier of topological insulators, theoretical and experimental physicists have been studying the surfaces of these unique materials for insights into the behavior of electrons that display some very un-electron-like properties.

In topological insulators, electrons can behave more like photons, or particles of light. The hitch is that unlike photons, electrons have a mass that normally plays a defining role in their behavior. In the world of quantum physics, where everyday materials take on surprising and sometimes astonishing properties, electrons on the outer surface of these insulators behave and look uncharacteristically like light.

These unique properties have piqued the interests of scientists who see future applications in areas such as quantum computing and spintronics, or other realms rooted in the manipulation of electronic properties. The early challenge to those researchers is to begin to understand some simple ground rules for controlling these materials.

Boston College researchers report that the placement of tiny ripples on the surface of a topological insulator engineered from bismuth telluride effectively modulates so-called Dirac electrons so they flow in a pathway that perfectly mirrors the topography of the crystal's surface.

Associate Professor of Physics Vidya Madhavan and Assistant Professor of Physics Stephen Wilson report in the current online edition of Nature Communications that scanning tunneling microscopy is capable of revealing the characteristics of these tiny waves as they rise and fall, enabling the researchers to draw a direct connection between the features of the ripples and modulation of the waves across the material's surface.

Instead of chaotic behavior, the electrons flow in a path that mirrors the metal composite's surface, the team reports in an articled titled "Ripple-modulated electronic structure of a 3D topological insulator."

"What we've discovered is that electrons respond beautifully to this buckling of the material's surface," said Madhavan, the project director.

So harmoniously do the waves flow across the ripples – placed approximately 100 nanometers apart – that the researchers say further modifications of the crystal's "nanoscale landscape" could produce enough control to produce a one-dimensional quantum wire capable of carrying current with no dissipation.

The rippled surface appears to exert greater control and run less risk of creating imperfections than other methods, such as introducing chemical dopants, used in attempts to modulate the flow of electrons on the surface of other topological insulators, the researchers found.

Madhavan said the team had to provoke the electrons, which lay placidly atop the surface-state of the insulator, much like the glassy surface of an undisturbed lake. The team disrupted the electrons by introducing impurities, which had an effect similar to that of dropping a stone in a calm lake. This provocation produced waves of electrons that behave like waves of light as they travel pathways that mirror the contours created in the crystal.

"We did not expect the electrons to follow the topography," said Madhavan. "The topography imposes a sinusoidal potential upon the waves. The ripples create that potential by giving the electrons a landscape to follow. This is a way of possibly manipulating these electrons in topological insulators."

In addition to Madhavan and Wilson, the project team included post-doctoral researcher Yoshinori Okada and graduate students Wenwen Zhou, Daniel Walkup and Chetan Dhital.

NOTE: The report "Ripple-modulated electronic structure of a 3D topological insulator" can be cited via a digital object identifier (DOI) number. The DOI for this article is 10.1038/ncomms2150

Ed Hayward | EurekAlert!
Further information:
http://www.bc.edu

More articles from Physics and Astronomy:

nachricht A better way to weigh millions of solitary stars
15.12.2017 | Vanderbilt University

nachricht A chip for environmental and health monitoring
15.12.2017 | Friedrich-Alexander-Universität Erlangen-Nürnberg

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>