Bose-Einstein condensate: Magnetic particles behave repulsively

By University of Munster Posted on Phys.org

ABOUT THE IMAGE: The researchers used a microwave resonator (brown) that generated fields with frequencies in the microwave range, which excited the magnons in an yttrium iron garnet film (red) and formed a Bose-Einstein condensate. An inhomogeneous static magnetic field created forces acting on the condensate. Using probing laser light (green) focused on the surface of the sample, the researchers recorded the local density of the magnons and were able to observe their interaction in the condensate (Brillouin light scattering spectroscopy). Credit: I. V. Borisenko et al./ Nature Communications

Data transmission that works by means of magnetic waves instead of electric currents: For many scientists, this is the basis of future technologies that will make transmission faster and individual components smaller and more energy-efficient. Magnons, the particles of magnetism, serve as moving information carriers. Almost 15 years ago, researchers at the University of Münster (Germany) succeeded for the first time in achieving a novel quantum state of magnons at room temperature—a Bose-Einstein condensate of magnetic particles, also known as a ‘superatome,’ i.e. an extreme state of matter that usually occurs only at very low temperatures.

Since then, it has been noticeable that this Bose-Einstein condensate remains spatially stable—although the theory predicted that the condensate of magnons, which are attractive particles, should collapse. In a recent study, the researchers have now shown for the first time that the magnons within the condensate behave in a repulsive manner, which leads to the stabilization of the condensate. “In this way, we are resolving a long-standing contradiction between the theory and the experiment,” says Prof. Sergej O. Demokritov who led the study. The results may be relevant for the development of future information technologies. The study was published in the journal Nature Communications.

Background and method:

What is special about the Bose-Einstein condensate is that the particles in this system do not differ from each other and are predominantly in the same quantum mechanical state. The state can therefore be described by a single wave function. This results, for example, in properties such as superfluidity, which is characterized by its zero dissipation during the motion of the condensate at low temperatures. The Bose-Einstein condensate of magnons is so far one of the few so-called macroscopic quantum phenomena that could be observed at room temperature.

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