Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Rapid journey through a crystal lattice

15.01.2015

Researchers from the TU München and the Max Planck Institute of Quantum Optics measure how long electrons need to travel through single atomic layers.

The time frames, in which electrons travel within atoms, are unfathomably short. For example, electrons excited by light change their quantum-mechanical location within mere attoseconds. An attosecond corresponds to a billionth of a billionth of a second.


Prof. Reinhard Kienberger at the attosecond beamline where the experiments were carried out.

(Photo: Thorsten Naeser)


Fig. 2

(Graphic: Christian Hackenberger)

But how fast do electrons whiz across distances corresponding to the diameter of individual atomic layers? Such distances are but a few billionths of a metre. An international team of researchers led by Reinhard Kienberger, Professor for Laser and X-Ray Physics at the TUM and Head of a Research Group at the Max Planck Institute of Quantum Optics investigated the travel times of electrons over these extremely short distances.

To do so, the physicists applied a defined number of layers of magnesium atoms on top of a tungsten crystal. The researchers directed two pulses of light at these samples. The first pulse lasted approximately 450 attoseconds, at frequencies within the extreme ultraviolet. This light pulse penetrated the material and released an electron from a magnesium atom in the layer system as well as from an atom in the underlying tungsten crystal. Both the electrons that were set free stemmed from the immediate vicinity of the nucleus.

Once released, the "tungsten electron" and the "magnesium electron" travelled through the crystal to the surface at which point they left the solid body. (electrons from the tungsten crystal managed to penetrate up to four layers of magnesium atoms.) There, the particles were captured by the electric field of the second pulse, an infrared wave train lasting less than five femtoseconds.

As the "tungsten electron" and the "magnesium electron" reached the surface at different times due to different path lengths, they experienced the second pulse of infrared light at different times. That is, they were exposed to different strengths of the oscillating electric field. As a result, both particles were accelerated to varying degrees. From the resulting differences in the energy of the electrons, the researchers were able to determine how long an electron needed to pass through a single layer of atoms. The measurements determined that a "tungsten electron" is delayed when travelling through a layer of magnesium atoms by approximately 40 attoseconds, i.e., this is exactly the time required to travel through this layer.

The experiments provide insight into how electrons move within the widely unknown microcosm. Knowing how fast an electron travels from one place to the next is of substantial importance for many applications: "While a large number of electrons are able to cover increasingly large distances in today's transistors, for example, individual electrons could transmit a signal through nanostructures in future", explains Prof. Reinhard Kienberger. "As a result, electronic devices like computers could be made to be several times faster and smaller." Thorsten Naeser

Fig. 2: A laser pulse (red) and an extreme ultraviolet attosecond pulse (violet, 1 as =10 to the minus 18 s) hit a surface made of a few layers of magnesium atoms (dark blue) which is on top of a tungsten crystal lattice (green). After the XUV pulse has released electrons from the inner core of the tungsten atoms the physicists determine the time the electrons need for penetrating the magnesium layers by applying the NIR laser pulse.

Original publication:
S. Neppl, R. Ernstorfer, A.L. Cavalieri, C. Lemell, G. Wachter, E. Magerl, E.M. Bothschafter,
M. Jobst, M. Hofstetter, U. Kleineberg, J.V. Barth, D. Menzel, J. Burgdörfer, P. Feulner, F. Krausz and R. Kienberger
Direct observation of electron propagation and dielectric screening on the atomic length scale
Nature 15 January 2015

For more information, please contact:
Prof. Dr. Reinhard Kienberger
Max Planck Institute of Quantum Optics and
Chair of Laser and X-ray Physics, E11
Faculty of Physics, TU Munich
James-Franck-Str., 85748 Garching
Phone: +49 (0)89 / 289 - 12840 / Fax: -12842
E-mail: reinhard.kienberger@tum.de

Weitere Informationen:

http://www.e11.ph.tum.de

Dr. Olivia Meyer-Streng | Max-Planck-Institut für Quantenoptik

More articles from Physics and Astronomy:

nachricht SF State astronomer searches for signs of life on Wolf 1061 exoplanet
20.01.2017 | San Francisco State University

nachricht Molecule flash mob
19.01.2017 | Technische Universität Wien

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: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>