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Magnetic Bose-Einstein-condensation achieved at room temperature

29.09.2006 - (idw) Westfaelische Wilhelms-Universität Münster

Physicists from the University of Muenster, Germany, realized novel quantum state of magnetic quantum waves without any cooling Bose-Einstein-condensation (BEC) is one of the most fascinating phenomena, illustrating the quantum nature of matter. Theoretically predicted by Satyendra Nath Bose and Albert Einstein in 1924, it describes the formation of a collective super-quantum state in a gas of identical particles (Bose particles). Typically, BEC takes only place if the density of the particles exceeds a critical value. To reach this value in turn, one has either to decrease the temperature of the particles or to increase their density. The first way implies experiments at temperatures which are very close to the absolute zero. Being long time one of the biggest experimental challenges of the century, the observation of BEC in ultra-cold diluted alkali gases was awarded in 2001 with the Nobel Prize in physics. Since this time, it seemed impossible to observe BEC of atoms at room temperature, since the necessary density exceeds all achievable gas densities. Atoms at such densities form solids or liquids.
In contrast, magnon gases - quanta of magnetic waves in solids - exist at room temperature in the gas state. Their density however was up to now too small to reach the BEC-transition.

A group of physicists led by Prof. Sergej Demokritov from the Institute of Applied Physics, University of Münster, in cooperation with physicists from Kaiserslautern University of Technology (Germany), Oakland University (USA), and Kiev University (Ukraine) has recently found a tricky way to enhance the number of magnons in the gas significantly by exciting additional magnons using microwaves. Thus, the number of magnons in the gas could be increased considerably. Although the additional magnons exist only during one millionth of a second, the scientists were able to investigate the gas behaviour using a laser probe beam technique. Thus, the scientists from Münster who are performing their work in the Münster Center for Nonlinear Science, have succeeded to show that additional magnons in fact initiate the condensation of magnons in a collective quantum state even at room temperature, as it was predicted by A. Einstein. A report on this work has been recently published in Nature.
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