Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A novel vanishing act

14.02.2011
Microwave photons can nullify the conductivity of electrons confined to the surface of liquid helium

Trapping electrons in a flat plane prevents them from moving freely in the third dimension and opens the door to a whole range of unusual physics. These effects are harnessed, for example, in modern ultrafast transistors, which confine electrons to thin layers of high-quality semiconductor crystals such as gallium arsenide.

But scattering from impurities in semiconductors can mask the deeper underlying physics of these so-called two-dimensional electron gases (2DEGs). Liquid helium may provide an alternative to semiconductors since it is largely impurity free. Using this approach, Denis Konstantinov and Kimitoshi Kono from the RIKEN Advanced Science Institute have demonstrated a novel effect where light totally switches off the conductivity of 2DEGs[1].

Two-dimensional electron gases form naturally at the surface of helium because an intrinsic energy barrier prevents electrons from penetrating any deeper into the liquid. These gases vary markedly from their three-dimensional counterparts because the electron motion in one direction becomes quantized—that is, their velocity in this direction is governed by quantum mechanics and is restricted to a range of discrete values.

Konstantinov and Kono cooled liquid helium-3 to 0.3 kelvin. They supplied electrons from a nearby hot filament, and applied voltage to a plate below the helium to control the number of electrons per unit area. Then, they fired microwave radiation at the 2DEG (Fig. 1) and measured the longitudinal conductivity— the current induced by an electric field applied along one direction—as a function of external magnetic field. They saw that the conductivity periodically fell to zero as they increased the magnetic field. When they switched off the source of microwave photons, however, this effect ceased.

This previously unidentified nullifying effect of microwave photons on conductivity is a consequence of energy-conserved scattering of the liquid helium’s electrons between different energy states—specifically, the first excited and ground sub-bands. “When the electrons stay in the ground sub-band, the effects are rather dull,” says Kono. “In our experiment, absorption of microwave photons transfers electrons to a higher energy sub-band,” Konstantinov adds. “As we change the magnetic field, the energies of states in two subbands cross, and scattering redistributes electrons between the sub-bands.”

Kono and Konstantinov believe that the result will lead to the observation of more novel phenomena in these two-dimensional systems when they are shifted out of their equilibrium state. “The study of nonequilibrium transport in the extremely clean helium system will complement studies of electron transport in semiconductors,” explains Konstantinov.

The corresponding author for this highlight is based at the Low Temperature Physics Laboratory, RIKEN Advanced Science Institute.

Journal information

[1] Konstantinov, D. & Kono, K. Photon-induced vanishing of magnetoconductance in 2D electrons on liquid helium. Physical Review Letters 105, 226801 (2010).

gro-pr | Research asia research news
Further information:
http://www.riken.jp
http://www.researchsea.com

More articles from Physics and Astronomy:

nachricht Ultra-compact phase modulators based on graphene plasmons
27.06.2017 | ICFO-The Institute of Photonic Sciences

nachricht Smooth propagation of spin waves using gold
26.06.2017 | Toyohashi University of Technology

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: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Touch Displays WAY-AX and WAY-DX by WayCon

27.06.2017 | Power and Electrical Engineering

Drones that drive

27.06.2017 | Information Technology

Ultra-compact phase modulators based on graphene plasmons

27.06.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>