[20.12.2023] A little (early) Christmas present for us and you: The new SFB1242 podcast is now online. In the first episode, Axel Lorke explains what is hidden behind the complicated name of the Collaborative Research Center and how such an SFB actually works. From now on, we will publish new episodes every month. Always on the 12th of the month at 12:42 p.m. Have fun listening.

[15.11.2023] When sunlight is converted into electricity, energy is lost and efficiency decreases - the solar cell becomes warm instead of delivering electrical power. The same applies to transportation in our electricity grid, where around 6% of the energy used is converted into heat, among other things, and is lost electrically. Computer chips also have to be cooled at great expense so that the unnecessary waste heat does not melt the electronics. One reason for this is the way electrons are transported in a metal wire. These often do not move along a ballistic trajectory, i.e. undisturbed in a straight line, but collide with other electrons, which leads to an inefficient zigzag movement. These collisions distribute the energy between the electrons and the ion hulls and generate heat. Markus Heckschen, together with a number of colleagues from the Collaborative Research Centre 1242, has now been able to analyze the flow of electrons with extremely high time resolution in iron-gold crystal layers in real time and model the scattering processes. A better understanding of how electrons move, combined with further analysis of the interaction between electrons and the crystal lattice, could potentially reduce a lot of waste heat caused by frictional losses in electrical and electronic components.

A crystal made of iron and gold was chosen as the test material. The advantage of these materials is that they fit together extremely well like puzzle pieces and there is no disruptive lattice displacement, which minimizes interface effects. The thickness of the gold layer was specifically altered and high-resolution electron spectroscopy was used to determine how much energy the electrons excited in the iron had lost on their flight through the gold. This required a time resolution of just 0.000 000 000 000 01 seconds. Thin layers and a trajectory transverse to the gold layer enabled the desired ballistic transport, thicker material and diagonal trajectories led to super-diffusive transport, in which there are already a few collisions between electrons, through to diffusive transport, in which electrons collide so often that their original kinetic energy is almost completely converted into heat. The angle of penetration of the electrons also plays an important role here. This knowledge could be used to produce an energy filter that would allow electrons to penetrate the material at the desired angle and thus enable a higher proportion of ballistic transport.

Publication in PRX Energy:
Spatio-Temporal Electron Propagation Dynamics in Au/Fe/MgO(001) in Nonequilibrium: Revealing Single Scattering Events and the Ballistic Limit. Markus Heckschen, Yasin Beyazit, Elaheh Shomali, Florian Kühne, Jesumony Jayabalan, Ping Zhou, Detlef Diesing, Markus E. Gruner, Rossitza Pentcheva, Axel Lorke, Björn Sothmann, and Uwe Bovensiepen. PRX Energy 2, 043009

[08.11.2023] A method developed at the UDE makes it possible to read data from noisy signals: Theoretical physicists and their experimental colleagues have collaborated on this and published their findings in the current issue of the renowned journal "Physical Review Research". The method they describe could also be significant for quantum computers.

You know it from the car radio: the weaker the signal, the more disturbing the noise. This is even more true for laboratory measurements. Researchers from the Collaborative Research Center 1242 and the Center for Nanointegration (CENIDE) at the UDE have now described a method for extracting data from noise.

What is a bit in a convantional computer, i.e. state 1 (current on) or state 0 (current off), is taken over in the quantum computer by the quantum bits, or qubits for short. To do this, they need defined and distinguishable states, but they can overlap at the same time and therefore enable many times the computing power of a current computer. This means they could also be used where today's supercomputers are overtaxed, for example in searching extremely large databases.

In Collaborative Research Center 1242, the smallest structures and their changes are studied, including quantum dots. These nanometer-sized structures can be tailored in their electronic and optical properties in the laboratory. Put simply, their electrons can assume two different directions of rotation ("spin up" and "spin down"). This is how the qubits needed for quantum computers can be realized. These should be stable for as long as possible so that no information is lost. "With our novel technique, we were able to demonstrate that spin states can be specifically prepared and at the same time determine how long such a state is maintained," explains Dr. Eric Kleinherbers, until recently a postdoc in the Theoretical Physics group headed by Prof. Dr. Jürgen König, now at the University of California, Los Angeles.

For this purpose, a quantum dot sample was permanently exposed to an exciting laser and the resulting noise was recorded over a long period of time. The theoretical physicists around Kleinherbers succeeded in extracting the lifetime of the spin states from this apparently random optical signal. Rolf Landauer, a pioneer of information theory, had already predicted this finding in 1998 and summarized it with the phrase "The noise is the signal!" The technique used now makes it possible to re-evaluate even older, seemingly useless data and to discover signals that had previously remained hidden.

Picture: View into the open cryostat: In operation, the slide with mounted sample is analyzed in a vacuum at around -270°C.

Additional information:
Eric Kleinherbers, Theoretische Physik, Tel. 0203/37 9- 3322, eric.kleinherbers@uni-due.de

Editor: Peter Kohl, SFB 1242, Tel. 0203/37 9-2822, peter.kohl@uni-due.de

[06.10.2023] The beginning of October is Nobel Prize Week every year. The Nobel Committee announces the laureates, who are awarded annually on December 10 (the anniversary of Alfred Nobel's death). This year, two topics have been selected that the SFB1242 is also working on intensively. The Nobel Prize in Physics goes to Pierre Agostini, Ferenc Krausz and Anne L'Huillier "for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter". Attoseconds are extremely short, the billionth part of a billionth of a second! Light needs just three attoseconds to move even one nanometre or about 200,000 attoseconds for the width of a human hair. The three researchers created the basis for a new approach to the world of atoms and molecules. In our Collaborative Research Centre, a whole series of subprojects use related ultrafast methods in experiments. Subproject A05 (femtosecond time-resolved spectroscopy in the soft X-ray range for element-specific analysis in complex nanostructures) uses the generation of so-called high harmonics to produce X-ray pulses with extremely short pulse durations, which make it possible to observe excitations in materials virtually in slow motion.

The announcement of the winners of the Nobel Prize for Chemistry followed one day later. Moungi G. Bawendi, Louis E. Brus and Alexei I. Ekimov received it for their work on quantum dots, semiconductor structures also called artificial atoms. This topic is addressed, among others, in sub-project A01, which deals with "Time-resolved electrical non-equilibrium spectroscopy on artificial atoms and molecules".

Uwe Bovensiepen, spokesperson of the CRC 1242, is pleased with the prize winners: "I am particularly pleased with this year's awarding of the Nobel Prizes. We have been using the methods of ultrafast spectroscopy very successfully in our Collaborative Research Centre for many years. Anne L'Huillier is a very respected colleague, as are the other prize winners, and has also been a guest in our colloquium Quantum dots and related nanostructures also play a role in our work. So both Nobel Prizes are very close to the scientific questions we pursue at the UDE." We are currently planning an evening event with lectures on the Nobel Prize topics. As soon as a date has been set, we will announce it here.

[02.10.2023] On Friday, 29.09.2023, the Night of Physics took place at the Duisburg campus. From 5 p.m., young and old were invited to be whisked away into the world of physics. There was something for everyone: laboratory tours, lectures on a wide range of topics, information stands on studying and research and, of course, lots to try out and take part in.
Anyone who wanted to find out more about airplanes, quantum effects, life on Mars, magnets or photoluminescence could join one or more of the many presentations.

Prefer practice rather than theory? No problem! Of course we were prepared for that: Have you ever seen a maglev train in action? Assembled a "Joule-Thief" yourself with solder? Painted with light? Let a dishwashing brush whizz across the floor? Used a thermal imaging camera or an electron microscope? Of course, there were not only these and many other gimmicks, but the physical effect was also explained directly. Of course, refreshments were also provided in between and so, after a total of 6 hours of knowledge and amazement, the Night of Physics came to an end. We are delighted that so many visitors were there and that some of them chatted with us and the professors and lecturers until the very end and got to know the versatility of physics.

Original text: Jana Schumann

[25.09.2023] Since 2018, the Equal Opportunities Working Group of the DPG has featured a female physicist every week - in calendar week 38, Lea Kämmerer (AG Wende, project A05) was in the portrait. Lea works on spin crossover molecules with a focus on the investigation of ultrafast dynamics by using time-resolved X-ray absorption spectroscopy. She has already told us what this means and what her everyday work is like for the SFB podcast, which will start soon. Until the episode with Lea is released, you can read more about her as female Physicist of the Week here:

[September 2023] Lukas Madauß has won the GANIL PhD Award for his PhD, which he completed in the group of Marika Schleberger at the end of 2021. In his thesis "Structurally modified two-dimensional materials for membrane applications", Lukas worked on the use of 2D materials in membrane applications. Among other things, he bombarded samples with ions at GANIL to increase their porosity. Lukas' work also includes the development of sample preparation methods that we use in project C05.

Congratulations Lukas!

[20.08.2023] The title of "Best Lecturer" in the first stage of medical training was awarded to Martin Paul Geller this summer. He gave the lecture "Physics for Physicians" to students in the first semester and was evaluated by the participants at the end. We are delighted that the role of physics in medicine and dedicated teaching have been recognized in this way.

[August 2023] Marika Schleberger’s working group had two visitors from Italy for three weeks! Thanks to the guest programme of the CRC 1242, Ofelia Durante and Loredana Viscardi from Antonio Di Bartolomeo's group were able to travel from Salerno (near Naples) to learn various steps of sample preparation developed by Stephan Sleziona for the CRC 1242. More specifically, the two, also with support of Osamah Kharsah and Leon Daniel, made pn junctions from black phosphorus and MoS₂, learning all the process steps from MoS₂ growth to photolithography (for electrical contacting of the pn junctions). We are looking forward to exciting results on these samples and a continued successful cooperation between our two groups.

[16.08.2023] The work on the ps ion source in project C05 has now made a significant step forward. Our PhD candidate Lukas Kalkhoff was able to demonstrate that the ion pulses generated with the new source are only 18 picoseconds short! This is another order of magnitude faster than our own previous record by A. Golobmbek et al. with 180 ps. The details can be found in Lukas' paper Phys. Rev. Res. which has now been accepted for publication.

[19.06.2023] Finally summer, finally (almost) vacations and therefore: finally Freestyle Physics again! Traditionally held in the last full week of school before the vacations, this year we were once again able to welcome over 1000 pupils from almost one hundred schools from all over Germany. Solutions were presented and evaluated over four days of competition. This time, the task was to build a bridge out of shashlik skewers that was as stable as possible but also as light as possible, and in the "crazy race", a means of transportation had to be constructed that could cover a defined distance in one minute - but without tires or wheels! In the crash test, the vehicles were allowed to roll, but were abruptly stopped by an obstacle. Whoever lost the least water from an installed cup was the winner. And as always, numerous water rockets were launched into the sky on the last day. It was a pleasure again and we can hardly wait for next summer.

[05.06.2023] Science and music on one stage - can that work? Axel and Nicolas proved it together with the Klangkraft Orchestra. In two sold-out shows in the Volksbank Rhein-Ruhr auditorium, all those involved showed how music and physics can be combined. With spherical sounds, unusual rhythms, familiar melodies, exciting experiments and randomly thrown together compositions, this concert was truly chaotic. Just as it should be.

[01.06.2023] Sometimes the usual university premises should be left behind for learning and teaching. Once a year, the PhDs from the Collaborative Research Center retreat to the PhD retreat to talk about their research and their doctorate and to gain new impetus in workshops. Nicolas and Peter gave a two-day workshop on social media and science communication, Gérald Kämmerer spoke on artificial intelligence and a third workshop dealt with the topics of time and team management.

[30.05.2023] Science out of the university and into the city. What we do again and again with our events is a tried and tested concept at Pint of Science. Scientists around the world get out of the lab and into the pub in May to talk about their research. Duisburg also took part for the first time with two events. The topics were very different and covered a broad spectrum on the first evening, "Real, virtual and false realities - urban living spaces, fake news and virtual exhibitions", with presentations from medicine, the Learning Lab and the Chair of Psychological Research Methods. The second evening was entitled "On a small and large scale - from materials and energy sources of the future to the foundations of our world" and dealt with hydrogen, the production of electrodes and Axel Lorke spoke on quantum mechanics.

[24.05.2023] Can we stop time with light? Why do we need lasers in the laboratory? How is the world's fastest movie made? We used various experiments to get to the bottom of these questions when ten schoolchildren visited our "fastest laboratory in the world". And it wasn't just us who asked questions that day, but also the young scientists. It's always great for us to experience this curiosity. If you would like to visit our school lab, please register for a visit at schuelerlabor@sfb1242.de

[03.03.2023] At the Spring Meeting of the German Physical Society in Dresden in March 2023, Fabio Rimek won first place in the poster competition with his poster "Magnetic Field-Dependence of the Auger-Recombination Rate in a Self-assembled Quantum Dot". Congratulations, Fabio.

[22.03.2023] The Ph.D. students Lea Spieker (AG Wende, project A05) and Gérald Kämmerer (AG Kratzer, project B02) have successfully applied for a Ph.D. Focus Session for the upcoming DPG of the SKM section in Dresden.

In their session, they want to emphasize the gap between theory and experiment on the topic of non-equilibrium dynamics. Four high-class speakers: Sangeeta Sharma, Cyrille Barreteau, Julia Stähler and Emmanuelle Jal will give talks on femtomagnetism, spin-switchable molecules, photodoping and ultrafast magnetization effects. The session will conclude with a podium discussion.

Location and time: 29.03.2023 15:00-18:00 in HSZ 02.
Abstracts can be found here: https://www.dpg-verhandlungen.de/year/2023/conference/skm/part/ma/session/30

[15.03.2023] At the end of November, a ransomeware attack occurred at the University of Duisburg-Essen. All systems were shut down as quickly as possible and disconnected from the network to prevent further damage. Slowly, step by step, the university is returning to normal operation - and our website is now also available again. We are in the process of adding some information and of course we are also working on new things. Stay tuned!

[06.02.2023] After the DPG is before the DPG. Last year, Project Ö had the pleasure of giving a talk in Regenburg on the topic of "Science communication - for whom actually?" and were delighted at how full the lecture hall became. Project Ö will be back in Dresden in March 2023, this time even with a panel discussion in the lunchtime track with Ulrich Bleyer (Urania Berlin) and Samuel Ritzkowski (young DPG), as well as a whole Focus Session with examples from science communication through invited talks and contributions.

Abstracts can be found here

[22.03.2023] "What is the current status, what scientific results have there been in recent years and where do we want to go?" These and other questions were discussed at our CRC exchange meeting at the Möhnesee. Currently, our Collaborative Research Center is in its second funding period - and the application for the third funding period will follow soon. The special thing about this meeting was that the main scientific contributions were presented by the Ph.D. students and so they could present themselves and their work to the other working groups. While the PIs planned the future of the CRC in the second half of the week, the Ph.D. students used the time for workshops and further training on topics such as "storytelling" or "poster design".