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International Collaboration At TU Dort­mund University

German and Russian physicists study magnetic properties of promising materials

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perovskite crystal structure © Archiv​/​TU Dort­mund

In the German-Russian Collaborative Research Center CRC/Transregio 160, “Coherent manipulation of interacting spin excitations in tailored semiconductors,” physicists from TU Dort­mund University, the Russian Ioffe Institute, and St. Petersburg State University are focusing on the intrinsic angular momentum of electrons in semiconductors. This quantum-mechanical property, the so-called spin, influences the magnetic characteristics of a material and can be selectively controlled by a magnetic field. One team is dedicated to the spin properties in perovskite crystal structures, which are currently receiving a lot of attention as components for efficient solar cells. The physicists have published their findings in the current issue of the renowned scientific journal Nature Communications. This contribution represents the first systematic work on the spin properties of perovskite materials.

A few years ago, it was shown that a special class of perovskite crystal structures, so-called lead halides, can convert light into electricity very well. Since the manufacturing costs are low, they could be used to produce solar cells cost-effectively. Conversely, the perovskite crystal structures exhibit intense light emission when current flows through them. Thus they could also be used to manufacture light-emitting diodes.

Their practical versatility raises hopes for further applications as well: It should be possible to use light to spatially align the spins of crystal structures of charge carriers. With that, they could be used as storage media, in both classical and quantum technology fields, that would require very little energy to operate.

To do this, the scientists need to find out more about the spin properties of these crystal structures. For that purpose, a team around Dr. Vasilii Belykh at TU Dort­mund University has, for the first time ever, conducted systematic experiments to understand the spins themselves and how they interact with their environment.

A variety of possible uses

Specifically, the scientists studied CsPbBr3 perovskite crystals that were produced at ETH Zurich. The physicists observed what happens when short, intense laser pulses strike the crystal structures at low temperatures and in strong magnetic fields. Dr. Belykh and his colleagues found out, on the one hand, that the spins of the electrons in the crystals react strongly to the laser pulses. That means the spins can be influenced selectively. That alone makes the perovskite crystals interesting for possible use as a storage medium. On the other hand, they also exhibit an intense interaction with the atomic nuclei in the crystals. This interaction could be cleverly exploited to achieve significant further increases in the life span of a magnetic storage device – the in­for­mation should ultimately remain reliably stored on a hard disk.

With their models, scientists of the Ioffe Institute in St. Petersburg, which collaborates with TU Dort­mund University in the Collaborative Research Center, were able to provide excellent theoretical descriptions for the observations.

 

About the scientist

Vasilii Belykh came to Dort­mund as a postdoctoral researcher in 2015, to work in the German-Russian Collaborative Research Center 160. After more than three years, he returned to Russia in the fall of 2018 and now works as a senior scientist at the P. N. Lebedev Institute of the Russian Academy of Sciences in Moscow. The close ties to Dort­mund still exist, nonetheless, strengthened by mutual exchange visits.

 

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Location & approach

The campus of TU Dort­mund University is located close to interstate junction Dort­mund West, where the Sauerlandlinie A 45 (Frankfurt-Dort­mund) crosses the Ruhrschnellweg B 1 / A 40. The best interstate exit to take from A 45 is "Dort­mund-Eichlinghofen" (closer to Campus Süd), and from B 1 / A 40 "Dort­mund-Dorstfeld" (closer to Campus Nord). Signs for the uni­ver­si­ty are located at both exits. Also, there is a new exit before you pass over the B 1-bridge leading into Dort­mund.

To get from Campus Nord to Campus Süd by car, there is the connection via Vogelpothsweg/Baroper Straße. We recommend you leave your car on one of the parking lots at Campus Nord and use the H-Bahn (suspended monorail system), which conveniently connects the two campuses.

TU Dort­mund University has its own train station ("Dort­mund Uni­ver­si­tät"). From there, suburban trains (S-Bahn) leave for Dort­mund main station ("Dort­mund Hauptbahnhof") and Düsseldorf main station via the "Düsseldorf Airport Train Station" (take S-Bahn number 1, which leaves every 20 or 30 minutes). The uni­ver­si­ty is easily reached from Bochum, Essen, Mülheim an der Ruhr and Duisburg.

You can also take the bus or subway train from Dort­mund city to the uni­ver­si­ty: From Dort­mund main station, you can take any train bound for the Station "Stadtgarten", usually lines U41, U45, U 47 and U49. At "Stadtgarten" you switch trains and get on line U42 towards "Hombruch". Look out for the Station "An der Palmweide". From the bus stop just across the road, busses bound for TU Dort­mund University leave every ten minutes (445, 447 and 462). Another option is to take the subway routes U41, U45, U47 and U49 from Dort­mund main station to the stop "Dort­mund Kampstraße". From there, take U43 or U44 to the stop "Dort­mund Wittener Straße". Switch to bus line 447 and get off at "Dort­mund Uni­ver­si­tät S".

Dort­mund Airport offers flights to several destinations in Central Europe. There are regular connections to Katowice, Kraków, London and Munich. For the approximately 20km-trip from Dort­mund Airport to TU Dort­mund University, you can use a shuttle bus to the railway Station "Bahnhof Holzwickede", from which trains depart to Dort­mund main station (please visit Verkehrsverbund Rhein-Ruhr for more in­for­mation). Normally, the fastest way is to catch a taxi at Dort­mund Airport.

The H-Bahn is one of the hallmarks of TU Dort­mund University. There are two stations on Campus Nord. One ("Dort­mund Uni­ver­si­tät S") is directly located at the suburban train stop, which connects the uni­ver­si­ty directly with the city of Dort­mund and the rest of the Ruhr Area. Also from this station, there are connections to the "Technologiepark" and (via Campus Süd) Eichlinghofen. The other station is located at the dining hall at Campus Nord and offers a direct connection to Campus Süd every five minutes.