Physical Review Letters Editors' Suggestion

26.01.2015

According to the fundamental Bohr-van Leeuwen theorem, the state of a classical many-particle system cannot be altered by turning on a magnetic field: in particular, a liquid will remain a liquid and a crystal will remain a crystal. In an article in Physical Review Letters Dr. Torben Ott, Professor Michael Bonitz (Christian-Albrechts-Universität zu Kiel) und Professor Hartmut Löwen (Heinrich-Heine-Universität Düsseldorf) demonstrate, that this theorem can be „tricked“. In a series of exact Computer simulations a liquid layer of charged particles was cooled rapidly. According to the above theorem the fluid would crystallize instantaneously when it is cooled, no matter whether a magnetic field is present or not. However, in the presence of a strong magnetic field the system remained fluid for a very long time. In their paper the scientists presented a simple explanation that is sektched in the figure: the magnetic field prevents particles from reaching the energetically lowest state (crystal) by bending their trajectories away from that minimum (in the center of the figure).
 
This work is a collaboration of the SFB-TR24 and SFB-TR6.
 
Paper: "Magnetic field blocks two-dimensional crystallization in strongly coupled plasmas" by T.Ott, H. Löwen, and M. Bonitz, Physical Review Letters 111, 065001 (2013) 
 
Link: Press release of CAU Kiel and Heine University Düsseldorf