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)
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.
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
Dr. Olivia Meyer-Streng | Max-Planck-Institut für Quantenoptik
Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory
SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences