Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

MIT physicists get ultra-sharp glimpse of electrons

24.07.2007
MIT physicists have developed a spectroscopy technique that allows researchers to inspect the world of electrons confined to a two-dimensional plane more clearly than ever before.

Two-dimensional electron systems, in which electrons are walled in from above and below but are free to move in a plane as if they were placed on a sheet of paper, are rarely observed in the natural world.

However, they can be created in a laboratory and used, for example, in high-frequency amplifiers found in cell phones.

The new spectroscopy technique measures electron energy levels with 1,000 times greater resolution than previous methods, an advance that has "tremendous power to tell you what the electrons are doing," said MIT physics professor Ray Ashoori, author of a paper on the work published in the July 12 issue of Nature. This technique has already revealed some surprising behavior, and the researchers believe it will shed new light on many physical phenomena involving electrons.

Ashoori and postdoctoral associate Oliver Dial took advantage of a quantum phenomenon known as tunneling to create the most detailed image ever of the spectrum of electron energy levels in a 2D system.

The new spectroscopy technique relies on a phenomenon that defies the laws of classical mechanics. Electrons, because they exhibit wavelike behavior, can move between two locations separated by a barrier without having to pass over the barrier-a phenomenon known as "quantum tunneling."

"We anticipate that this technique will help us discover all kinds of new physics," said Ashoori. "We're looking into a realm that was just not visible to us before."

Electrons trapped in 2D systems exist in specific energy levels, just as electrons orbiting an atom's nucleus in three dimensions exist in distinct quantum energy levels. By measuring which energy levels are occupied, physicists can study how electrons behave together in large groups.

The researchers used short pulses of electricity to induce electrons to tunnel from a 2D system to a 3D system, and vice versa. By measuring the resulting voltage difference, they could calculate the energy states of the electrons in the 2D system.

The spectroscopy experiments were performed inside a semiconducting crystal cooled to 0.1 degrees above absolute zero.

Until now, the primary method for performing this kind of spectroscopy relied on photoemission. The new method has an energy resolution that is 1,000 times finer than the best photoemission measurements.

Physicists have also traditionally used "transport" techniques that measure electrical currents flowing in response to applied voltages to learn about 2D electron energy levels, but that technique only offers a partial look at what electrons are doing.

"Similar to creating small ripples on the surface of a sea, transport techniques only tell us about what is happening very close to the water's surface," said Dial. "Pictures made with this high-resolution spectroscopy provide, in essence, one of the first glimpses of the entire ocean in these systems and show what a beautiful and interesting world exists beneath the surface."

The research was conducted in collaboration with crystal growers at Alcatel-Lucent Bell Laboratories in Murray Hill, N.J., and funded by the Office of Naval Research and the National Science Foundation.

Elizabeth A. Thomson | MIT News Office
Further information:
http://www.mit.edu

More articles from Physics and Astronomy:

nachricht Structured light and nanomaterials open new ways to tailor light at the nanoscale
23.04.2018 | Academy of Finland

nachricht On the shape of the 'petal' for the dissipation curve
23.04.2018 | Lobachevsky University

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: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Structured light and nanomaterials open new ways to tailor light at the nanoscale

23.04.2018 | Physics and Astronomy

On the shape of the 'petal' for the dissipation curve

23.04.2018 | Physics and Astronomy

Clean and Efficient – Fraunhofer ISE Presents Hydrogen Technologies at the HANNOVER MESSE 2018

23.04.2018 | Trade Fair News

VideoLinks
Science & Research
Overview of more VideoLinks >>>