Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Kaiserslautern physicists observe diffusion of individual atoms in light bath

11.10.2016

In a combination of experiments and theory the diffusion of individual atoms in periodic systems was understood for the first time. The interaction of individual atoms with light at ultralow temperatures close to the absolute zero temperature point provides new insights into ergodicity, the basic assumption of thermodynamics. Quantum physicists at University of Kaiserslautern have published their results together with colleagues in the renowned scientific journal “Nature Physics”.

Diffusion is a universal physical phenomenon, describing the motion of particles in their particular environment, whether solid, liquid or gaseous. The first observation of Robert Brown and the subsequent explanation by Albert Einstein are already more than a hundred years old: Robert Brown observed the random, irregular dithering movement of pollen in a liquid.


Series of fluores-cence images, show-ing the diffusion of a single atom.

University of Kaiserslautern/Widera

Albert Einstein and his colleague Marian Smoluchowski interpreted this "Brownian motion" correctly as a result of random collisions of molecules of the liquid with the pollen. The diffusion in complex systems goes one step further and can have very diverse characteristics: Tumor movement in living organisms, DNA transport within cells, ion flow in batteries, moving atoms on surfaces - all these are diffusion processes in complex systems.

Uncovering of the underlying mechanisms is of great interest as these could reach far into daily applications one day. Physical studies of ultracold atoms, carried out at the University of Kaiserslautern, now provide an understanding of diffusion in periodic structures, relevant for various complex systems.

Physicists at the University of Kaiserslautern together with scientists from the Universities of Erlangen-Nuremberg and Kyoto in Japan have made an important step towards the fundamental understanding of complex diffusion and the interpretation of their experimental data. For the study, published in the prestigious journal Nature Physics, the Kaiserslautern team around Professor Widera (Department of Physics and State Research Center OPTIMAS) developed a novel model system:

A single atom is cooled by lasers near to absolute zero temperature and trapped by light within a near-perfect vacuum. The atom is then transferred into an environment of a light field in which the light-absorption and light-emission of the atoms act as collisions with other particles. In this environment, the diffusion can be readily set and the motion of the atom be tracked by a camera.

In parallel, theoretical physicists from Erlangen-Nuremberg and Kyoto developed a model for the description of the dynamics of the system. A central aspect here was to understand the processes in terms of the physical phenomenon of ergodicity. Due to the excellent agreement between experiment and theory, diffusion processes can now be understood beyond Brownian motion. These results have potentially an impact on the understanding of various complex systems in medicine, biology, physics and engineering in the future.

Fundamentals of diffusion

The motion of individual cells in the body or the transport of charge carriers in energy storage systems can be understood only in the context of the particular environment. The particles within the environment encounter permanent collisions with a cell or a carrier, thus influencing their motion. These processes can in many cases be described through Brownian motion by Einstein’s theory. Sometimes the observations can, however, not be described within this model, and in some cases this non-Brownian dynamics are not obvious at first glance. The scientists of the three universities have succeeded in showing both theoretically and experimentally, how the diffusion in certain complex systems can be characterized.

Ergodicity is a key to understanding complex diffusions

A central aspect of the study was to investigate the atomic system on time scales that are relevant for the establishment of ergodicity. Ergodicity is a basic assumption of thermodynamics and an important factor for the description of diffusion processes. In simple words, the ergodicity hypothesis states that in an ensemble of particles, the motion of a single particle is representative for the entire ensemble. This assumption is usually valid for all observed phenomena in our everyday lives. Strictly seen, this applies, nevertheless, for most systems only on very long time scales. The scientists could now show in their study that even seemingly "normal" diffusion processes in certain cases may violate ergodicity on surprisingly long time scales. These findings have interesting implications for understanding the diffusion in complex systems and can help, for example, to re-evaluate and interpret observations and measurements in biological systems.

The study was published in the renowned journal “Nature Physics”: „Nonergodic diffusion of single atoms in a periodic potential“.
DOI: DOI 10.1038/nphys3911

Further questions will be answered by:
Prof. Dr. Artur Widera
TU Kaiserslautern
Tel: 0631-205-4130
E-Mail: widera@physik.uni-kl.de

Katrin Müller | Technische Universität Kaiserslautern
Further information:
http://www.uni-kl.de

More articles from Physics and Astronomy:

nachricht Bridging the nanoscale gap: A deep look inside atomic switches
22.07.2019 | Tokyo Institute of Technology

nachricht Heat flow through single molecules detected
19.07.2019 | Okinawa Institute of Science and Technology (OIST) Graduate 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: Better thermal conductivity by adjusting the arrangement of atoms

Adjusting the thermal conductivity of materials is one of the challenges nanoscience is currently facing. Together with colleagues from the Netherlands and Spain, researchers from the University of Basel have shown that the atomic vibrations that determine heat generation in nanowires can be controlled through the arrangement of atoms alone. The scientists will publish the results shortly in the journal Nano Letters.

In the electronics and computer industry, components are becoming ever smaller and more powerful. However, there are problems with the heat generation. It is...

Im Focus: First-ever visualizations of electrical gating effects on electronic structure

Scientists have visualised the electronic structure in a microelectronic device for the first time, opening up opportunities for finely-tuned high performance electronic devices.

Physicists from the University of Warwick and the University of Washington have developed a technique to measure the energy and momentum of electrons in...

Im Focus: Megakaryocytes act as „bouncers“ restraining cell migration in the bone marrow

Scientists at the University Würzburg and University Hospital of Würzburg found that megakaryocytes act as “bouncers” and thus modulate bone marrow niche properties and cell migration dynamics. The study was published in July in the Journal “Haematologica”.

Hematopoiesis is the process of forming blood cells, which occurs predominantly in the bone marrow. The bone marrow produces all types of blood cells: red...

Im Focus: Artificial neural network resolves puzzles from condensed matter physics: Which is the perfect quantum theory?

For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.

Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...

Im Focus: Extremely hard yet metallically conductive: Bayreuth researchers develop novel material with high-tech prospects

An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".

The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on UV LED Technologies & Applications – ICULTA 2020 | Call for Abstracts

24.06.2019 | Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

 
Latest News

Bridging the nanoscale gap: A deep look inside atomic switches

22.07.2019 | Physics and Astronomy

Regulation of root growth from afar: How genes from leaf cells affect root growth

22.07.2019 | Life Sciences

USF geoscientists discover mechanisms controlling Greenland ice sheet collapse

22.07.2019 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>