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 Shape matters when light meets atom
05.12.2016 | Centre for Quantum Technologies at the National University of Singapore

nachricht Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

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: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

High-precision magnetic field sensing

05.12.2016 | Power and Electrical Engineering

Construction of practical quantum computers radically simplified

05.12.2016 | Information Technology

NASA's AIM observes early noctilucent ice clouds over Antarctica

05.12.2016 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>