Bose-Einstein condensate: Magnetic particles behave repulsively

April 24, 2020

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 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.

Previously, the processes in the condensate had been studied exclusively in homogeneous magnetic fields - i.e. in magnetic fields that are equally strong at every point and in which the field lines point uniformly in one direction. As previously, using a microwave resonator, which generated fields with frequencies in the microwave range, the researchers excited magnons forming a Bose-Einstein condensate. In the current experiment, they, however, introduced an additional so-called potential well, which corresponds to inhomogeneous static magnetic field, which creates forces acting on the condensate. This enabled the scientists to directly observe the interaction of the magnons in the condensate.

For this purpose, they used a method of Brillouin light scattering spectroscopy. This involved recording the local density of the magnons with probing laser light focused on the surface of the sample. On this way, the researchers recorded the spatial redistribution of the condensate density at different experimental conditions. The collected data allowed to draw the firm conclusion that the magnons in the condensate interact in a repulsive manner, thereby keeping the condensate stable.

In addition, the researchers observed two characteristic times of dissipation, i.e. dissipation of energy and momentum from the condensate to other states. The time of momentum dissipation - the momentum describes the mechanical state of motion of a physical object - proved to be very long. "This may be the first experimental evidence for possible magnetic superfluidity at room temperature," emphasizes Sergej Demokritov.

Up to now, the use of condensates from magnetic particles has been made difficult mainly by the short lifetime of the condensate. "Our realization of moving condensate and investigation of magnon transport as well as discovery of two different times show that the life-time has nothing to do with the momentum dissipation of the moving condensate," says first author Dr. Igor Borisenko. The results could therefore open new perspectives for magnon applications in future information technologies.
-end-
Participating institutions:

In addition to researchers from the Institute of Applied Physics and the Center for Nanotechnology at Münster University, scientists from the University of Cologne, Texas A&M University and the Russian Academy of Sciences were involved in the study.

Original publication:

I. V. Borisenko et al. (2020): Direct evidence of spatial stability of Bose-Einstein condensate of magnons. Nature Communications; DOI: 10.1038/s41467-020-15468-6

University of Münster

Related Magnetic Fields Articles from Brightsurf:

Physicists circumvent centuries-old theory to cancel magnetic fields
A team of scientists including two physicists at the University of Sussex has found a way to circumvent a 178-year old theory which means they can effectively cancel magnetic fields at a distance.

Magnetic fields on the moon are the remnant of an ancient core dynamo
An international simulation study by scientists from the US, Australia, and Germany, shows that alternative explanatory models such as asteroid impacts do not generate sufficiently large magnetic fields.

Modelling extreme magnetic fields and temperature variation on distant stars
New research is helping to explain one of the big questions that has perplexed astrophysicists for the past 30 years - what causes the changing brightness of distant stars called magnetars.

Could megatesla magnetic fields be realized on Earth?
A team of researchers led by Osaka University discovered a novel mechanism called a ''microtube implosion,'' demonstrating the generation of megatesla-order magnetic fields, which is three orders of magnitude higher than those ever experimentally achieved.

Superconductors are super resilient to magnetic fields
A Professor at the University of Tsukuba provides a new theoretical mechanism that explains the ability of superconductive materials to bounce back from being exposed to a magnetic field.

A tiny instrument to measure the faintest magnetic fields
Physicists at the University of Basel have developed a minuscule instrument able to detect extremely faint magnetic fields.

Graphene sensors find subtleties in magnetic fields
Cornell researchers used an ultrathin graphene ''sandwich'' to create a tiny magnetic field sensor that can operate over a greater temperature range than previous sensors, while also detecting miniscule changes in magnetic fields that might otherwise get lost within a larger magnetic background.

Twisting magnetic fields for extreme plasma compression
A new spin on the magnetic compression of plasmas could improve materials science, nuclear fusion research, X-ray generation and laboratory astrophysics, research led by the University of Michigan suggests.

How magnetic fields and 3D printers will create the pills of tomorrow
Doctors could soon be administering an entire course of treatment for life-threatening conditions with a 3D printed capsule controlled by magnetic fields thanks to advances made by University of Sussex researchers.

Researchers develop ultra-sensitive device for detecting magnetic fields
The new magnetic sensor is inexpensive to make, works on minimal power and is 20 times more sensitive than many traditional sensors.

Read More: Magnetic Fields News and Magnetic Fields Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.