The interaction of electrons and matter is fundamental to material properties such as electrical conductivity. Electrons are scattering from atoms of the surrounding matter and can excite lattice oscillations, so called phonons, thereby transferring energy to the environment. The electron is therefore slowed which causes electrical resistance.
University of Stuttgart, 5. Physikalische Institut
Illustration of the system investigated: A highly excited Rydberg-atom, consisting of a single electron (blue), traveling on a large orbit far from the positively charged core (red). The Rydberg atom has the same spatial extent as the ultracold atomic cloud. The single electron is exciting oscillations, so called phonons, in the surrounding quantum gas.
However, in certain materials phonons can surprisingly cause the opposite effect, so called superconductivity, where the electrical resistance drops to zero. Understanding the interaction of electrons and matter is therefore important goal in order to both answer fundamental questions as well as to solve technical problems.
A single electron is best suited for systematic investigations of such processes. For the first time, physicists from Stuttgart have now realized a model system in the laboratory, where the interaction of a single electron with many atoms inside its orbital can be studied. These atoms are from an ultracold cloud near absolute zero, a so called Bose-Einstein condensate.
The basic idea now is simple: Instead of using a technically challenging electron trap, the scientists are using the fact that in nature electrons are bound to a positively charged atomic core. In a classical picture, they are travelling on ellipsoidal orbits around the core. These orbits are usually very small, typically in the range below one nanometer. In order to achieve an interaction between an electron and many atoms, an atom is excited from a cloud consisting of 100.000 atoms using laser light.
The orbit of a single electron then expands to several micrometers and a Rydberg atom is formed. On atomic length scales, this atom is huge, larger than most bacteria, which are consisting each of + several billions to trillions of atoms. The Rydberg atom is then containing tens of thousands of atoms from the cold cloud. Thus, a situation is realized where the electron is trapped in a defined volume and at the same time interacts with a large number of atoms.
This interaction is so strong that the whole atomic cloud, consisting of 100,000 atoms is considerably influenced by the single electron. Depending on its quantum state the electron excites phonons in the atomic cloud, which can be measured as collective oscillations of the whole cloud culminating in a loss of atoms from the trap.
The experimental observations in the group of Prof. Tilman Pfau could so far largely be explained by collaborative work with the theory group of Prof. Hans Peter Büchler. However, this work is only the basis for a series of further exciting experiments. According to the previous studies an electron is leaving a clear trace in the surrounding atomic cloud. Therefore imaging a single electron in a well defined quantum state seems to be feasible. Due to the impact on various fields, including quantum optics, these results were published in the highly respected journal Nature *).
This work has been realized within Sonderforschungsbereich SFB/TRR 21 (Control of quantum correlations in tailored matter) and has been supported by the Detusche Forschungsgemeinschaft DFG and the European Research Council.
*) J.B. Balewski, A.T. Krupp, A. Gaj, D. Peter, H.P. Büchler, R. Löw, S. Hofferberth and T. Pfau, Coupling a single electron to a Bose-Einstein condensate; Nature, doi:10.1038/nature12592Further information:
Andrea Mayer-Grenu | idw
When helium behaves like a black hole
22.03.2017 | University of Vermont
Astronomers hazard a ride in a 'drifting carousel' to understand pulsating stars
22.03.2017 | International Centre for Radio Astronomy Research
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
22.03.2017 | Materials Sciences
22.03.2017 | Physics and Astronomy
22.03.2017 | Materials Sciences