Lifetime of skyrmions


For decades, tuning energy barriers has been the main approach to develop information storage bits based on magnetic materials. It is common wisdom that the energy barrier should exceed the thermal energy by a factor of about 50 at room temperature to ensure reliable bit stability. In a study published in Physical Review B (Rapid Comm.) Skyrmion lifetime in ultrathin films Stephan von Malottki, Soumyajyoti Haldar, and Stefan Heinze in collaboration with Pavel Bessarab, who is staying for one year in the Heinze group with an Alexander von Humboldt fellowship, and Anna Delin (KTH Stockholm) reveal that this criterion does not hold for magnetic skyrmions. The attempt frequency - normally assumed to be constant - can change by orders of magnitude with skyrmion diameter and can become the decisive factor for skyrmion stability. This work opens new paths towards stabilizing sub-10 nm skyrmions at room temperature.

Novel effect of plasma-surface interaction discovered


A new mechanism of the interaction of ions with strongly correlated finite graphene-type fragments has been obtained: ions of certain energies create doublons in the target material. The results could allow to reversibly change the electronic properties of the material with potential applications for low-temperature plasmas. The results are published in:

Karsten Balzer, Maximilian Rodriguez Rasmussen, Niclas Schlünzen, Jan-Philip Joost, and Michael Bonitz,
Doublon formation by ions impacting a strongly correlated finite lattice system,
Phys. Rev. Lett. 121, 267602 (2018)

Press Release of Kiel University / Pressemitteilung der CAU Kiel

Breakthrough in warm dense matter research


The first ab initio results for the dynamic structure factor of the finite temperature electron gas are obtained and confirm the existence of a negative plasmon dispersion at strong coupling. The results are published in:

Tobias Dornheim, Simon Groth, Jan Vorberger, and Michael Bonitz,
Ab Initio Path Integral Monte Carlo Results for the Dynamic Structure Factor of Correlated Electrons: From the Electron Liquid to Warm Dense Matter,
Physical Review Letters 121, 255001 (2018)

Press Release of Kiel University / Pressemitteilung der CAU Kiel

Young researcher award


August 2018: Tobias Dornheim from the Statistical Physics group of Prof. Michael Bonitz (ITAP) wins the U30 Doctoral Scientist Award of the Plasma Physics Division of the Asian-Pacific Physical Society “for the invention of the permutation blocking path integral Monte Carlo method  for the ab initio simulation of the warm dense electron gas and constructing the key ingredient in warm dense matter physics”. The award is combined with combined with a talk at the annual meeting of the society, November 12-16 in Kanazawa, Japan.

Prediction of sub-10 nm skyrmion formation


Magnetic skyrmions are localized, stable magnetic whirls which could be used as bits to store information in future memory and logic devices. In a paper recently published in Physical Review B (Rapid Comm.) Prediction of sub-10 nm skyrmions in Pd/Fe bilayers on Rh(111) using first-principles calculations it is shown by Soumyajyoti Haldar, Stephan von Malottki, Sebastian Meyer and Stefan Heinze (CAU Kiel) in collaboration with Pavel Bessarab (Univ. of Iceland) that sub-10 nm size skyrmions can form in a new class of materials: 3d/4d transition-metal interfaces. By combining density functional theory and atomistic spin dynamics with the geodesic nudged elastic band method and transition state theory it is demonstrated that the lifetime of skyrmions with radii of 3 – 5 nm is up to an hour at temperatures of up to 40 K – significantly higher than experimentally observed for sub-10 nm skyrmions so far. The applied theoretical approach can guide future experimental efforts to explore skyrmions at novel interfaces.

Two "featured articles" in July issue of Physics of Plasmas for the Plasma Dynamics (Prof. Piel) and Experimental Plasma Physics (Prof. Benedikt) Groups


The articles of Oguz Han Asnaz Charging of an irregularly shaped particle in the sheath of an rf plasma"  and Hendrik Jung Experiments on wake structures behind a microparticle in a magnetized plasma flow" have been awarded "Featured Article" in the July issue of Physics of Plasmas. Furthermore, the cover page of the July issue features the article of Hendrik Jung presenting experiments and molecular dynamics simulations concerning the wake structure behind a particle in a magnetized flowing plasma.


Prof. Dr. Holger Kersten zum 1. Prodekan gewählt


Am 04.07.2018 wurde Prof. Dr. Holger Kersten (IEAP, AG Plasmatechnologie) vom Konvent der Mathematisch-Naturwissenschaftlichen Fakultät zum 1. Prodekan gewählt. Die Fakultät wird geleitet von dem Dekan Prof. Dr.Frank Kempken, bei der Führung der Fakultätsgeschäfte wird er durch den ersten Prodekan Prof. Dr. Holger Kersten unterstützt. Der erste Prodekan vertritt den Dekan in allen Angelegenheiten, besonders bei Berufungsverfahren und Habilitationen. Der Dekan sowie die Prodekane wurden vom Fakultätskonvent aus dem Kreis der ihm angehörenden Mitglieder jeweils für die Dauer von zwei Jahren gewählt. Sie üben diese Ämter nebenamtlich aus. Siehe auch: https://www.mnf.uni-kiel.de/de/dekanat-1/dek-info

EPS Poster Award für Viktor Schneider


Auf der 45. Konferenz für Plasmaphysik der Europäischen Physikalischen Gesellschaft (EPS) (siehe https://eps2018.eli-beams.eu/en/), die vom 02. bis zum 06. Juli 2018 in Prag stattfand, hat Viktor Schneider aus der AG Plasmatechnologie den EPS/PPCF Posterpreis für seine Arbeit "An optically trapped microparticle as plasma probe" gewonnen.

In seinen experimentellen Untersuchungen geht es um die Verwendung von Mikropartikeln als elektrostatische Sonden in der Plasmarandschicht einer Hochfrequenzentladung. Die Testpartikel werden in einer optischen Falle (laser tweezers) eingefangen und im Plasma bzw. in der Randschicht verschoben. Aus der resultierenden Kräftebilanz kann über die Partikelladung der Verlauf des elektrischen Feldes in der Randschicht bestimmt werden. Darüberhinaus hat Herr Schneider die Partikel mittels UV-Strahlung bzw. in einem kleinen Plattenkondensator so manipuliert, dass er deren Restladungen bei ausgeschaltetem Plasma ermitteln konnte.

Relais satellite for Chinese Chang'E4 lunar mission successfully launched


The relais satellite for the Chinese lunar mission Chang'E4 was successfully launched on May 21, 2018. Chang'E4 itself is foreseen to be launched in December this year and then fly to and land on the far side of the Moon. The relais satellite is needed for communication with the lander and its scientific payload. The Extraterrestrial Physics Division developed and built a radiation monitor which is part of the payload and is currently being tested together with the lander in Beijing.

There's a short article about it in Nature:

and a youtube video:

Earth moon satellite relation
(picture credit: LESEC)

Discovery of a novel spin structure


Today the interplay of exchange and Dzyaloshinskii-Moriya interaction (DMI) at transition-metal interfaces is a focus of research in condensed matter physics since it can lead to topologically non-trivial spin structures such as skyrmions and antiskyrmions which are promising for spintronic applications. Higher-order exchange interactions beyond pairwise Heisenberg exchange have received much less attention. The groups of Prof. Roland Wiesendanger (University of Hamburg) and of Prof. Stefan Heinze (CAU Kiel) now demonstrate based on spin-polarized scanning tunneling microscopy and density functional theory that higher-order exchange interactions can play a decisive role in transition-metal trilayers and that their competition with DMI can lead to novel types of spin structures (see figure). Their work recently published in Physical Review Letters "Competition of Dzyaloshinskii-Moriya and higher-order exchange interactions in Rh/Fe atomic bilayers on Ir(111)" also demonstrates that higher-order exchange needs to be taken into account in the search for novel transition-metal interfaces potentially promising for complex spin structures such as skyrmions.