Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Elusive Quasiparticles Realized

24.05.2012
In quantum physics physical processes in condensed matter and other many-body systems can often be described with quasiparticles.

In Innsbruck, for the first time Rudolf Grimm’s team of physicists has succeeded in experimentally realizing a new quasiparticle – a repulsive polaron – in an ultracold quantum gas. The scientists have published their results in the online issue of the journal Nature.


The potassium atom in the middle (blue) repulses the smaller lithium atoms (yellow). This creates a complex state, which can be described physically as a quasiparticle. In various ways it behaves like a new particle with modified properties. Graphics: Harald Ritsch

Ultracold quantum gases are an ideal experimental model system to simulate physical phenomena in condensed matter. In these gases, many-body states can be realized under highly controlled conditions and interactions between particles are highly tuneable. A research group led by Wittgenstein awardee Rudolf Grimm and START awardee Florian Schreck have now realized and comprehensively analyzed repulsive polarons for the first time. The scientists from the Institute of Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences and the Institute for Experimental Physics of the University of Innsbruck are international leaders in this field of research.

Elusive partners

To realize repulsive polarons experimentally, Rudolf Grimm and his research team produce an ultracold quantum gas consisting of lithium and potassium atoms in a vacuum chamber. They control particle interaction with electromagnetic fields, and by applying radio-frequency pulses they then drive the potassium atoms into a state where they repulse the surrounding lithium atoms. This complex state can be described physically as quasiparticle because, in various ways, it behaves like a new particle with modified properties. By analyzing the whole energy spectrum of the system, the researchers were able to demonstrate repulsive polarons. “This way we were able to realize and analyze not only attractive but also repulsive polarons,” says Prof Grimm. While attractive polarons have been studied before, the quantum physicist and his team have entered a completely new scientific field with these novel repulsive quasiparticles.

Ideal observation platform

In condensed matter these quasiparticles decay very quickly, which makes it nearly impossible to study them. But also in quantum gases the repulsive properties present difficulties: “Polarons can only exist in a metastable state,“ explains Rudolf Grimm “and their lifetime is crucial for our ability to investigate them at all. We were surprised to find that our polarons showed an almost ten times increased lifetime compared to earlier experiments in similar systems. Our experimental set-up, therefore, provides an ideal platform for a detailed analysis of many-body states that rely on repulsive interactions.“ As a next step the Innsbruck researchers are going to investigate whether separate domains where only lithium or only potassium atoms accumulate are created in a quantum gas consisting of repulsive particles. “This has been suggested in theoretical models but only now we will are able to investigate it experimentally.“

The scientists have published their results in the journal Nature. The experiment was carried out in close cooperation with two theoretical physicists from Denmark and Spain and is financially supported by the Austrian Science Fund within the Special Research Program FoQuS.

Publication: Metastability and coherence of repulsive polarons in a strongly interacting Fermi mixture, Christoph Kohstall, Matteo Zaccanti, Michael Jag, Andreas Trenkwalder, Pietro Massignan, Georg M. Bruun, Florian Schreck und Rudolf Grimm. Nature 2012

http://dx.doi.org/10.1038/nature11065

Contacts:
Univ.-Prof. Dr. Rudolf Grimm
Institute for Experimental Physics
University of Innsbruck
phone: +43 512 507 6300
email: Rudolf.Grimm@uibk.ac.at
web: http://www.ultracold.at
Dr. Christian Flatz
Public Relations
University of Innsbruck
phone.: +43 512 507 32022
mobil: +43 676 872532022
email: Christian.Flatz@uibk.ac.at

Dr. Christian Flatz | Universität Innsbruck
Further information:
http://www.ultracold.at
http://www.uibk.ac.at

More articles from Physics and Astronomy:

nachricht SF State astronomer searches for signs of life on Wolf 1061 exoplanet
20.01.2017 | San Francisco State University

nachricht Molecule flash mob
19.01.2017 | Technische Universität Wien

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>