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
New NASA study improves search for habitable worlds
20.10.2017 | NASA/Goddard Space Flight Center
Physics boosts artificial intelligence methods
19.10.2017 | California Institute of Technology
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
20.10.2017 | Information Technology
20.10.2017 | Materials Sciences
20.10.2017 | Interdisciplinary Research