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 Thin films from Braunschweig on the way to Mercury
19.10.2018 | Fraunhofer-Institut für Schicht- und Oberflächentechnik IST

nachricht Extremely close look at electron advances frontiers in particle physics
19.10.2018 | National Science Foundation

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: Goodbye, silicon? On the way to new electronic materials with metal-organic networks

Scientists at the Max Planck Institute for Polymer Research (MPI-P) in Mainz (Germany) together with scientists from Dresden, Leipzig, Sofia (Bulgaria) and Madrid (Spain) have now developed and characterized a novel, metal-organic material which displays electrical properties mimicking those of highly crystalline silicon. The material which can easily be fabricated at room temperature could serve as a replacement for expensive conventional inorganic materials used in optoelectronics.

Silicon, a so called semiconductor, is currently widely employed for the development of components such as solar cells, LEDs or computer chips. High purity...

Im Focus: Storage & Transport of highly volatile Gases made safer & cheaper by the use of “Kinetic Trapping"

Augsburg chemists present a new technology for compressing, storing and transporting highly volatile gases in porous frameworks/New prospects for gas-powered vehicles

Storage of highly volatile gases has always been a major technological challenge, not least for use in the automotive sector, for, for example, methane or...

Im Focus: Disrupting crystalline order to restore superfluidity

When we put water in a freezer, water molecules crystallize and form ice. This change from one phase of matter to another is called a phase transition. While this transition, and countless others that occur in nature, typically takes place at the same fixed conditions, such as the freezing point, one can ask how it can be influenced in a controlled way.

We are all familiar with such control of the freezing transition, as it is an essential ingredient in the art of making a sorbet or a slushy. To make a cold...

Im Focus: Micro energy harvesters for the Internet of Things

Fraunhofer IWS Dresden scientists print electronic layers with polymer ink

Thin organic layers provide machines and equipment with new functions. They enable, for example, tiny energy recuperators. In future, these will be installed...

Im Focus: Dynamik einzelner Proteine

Neue Messmethode erlaubt es Forschenden, die Bewegung von Molekülen lange und genau zu verfolgen

Das Zusammenspiel aus Struktur und Dynamik bestimmt die Funktion von Proteinen, den molekularen Werkzeugen der Zelle. Durch Fortschritte in der...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Conference to pave the way for new therapies

17.10.2018 | Event News

Berlin5GWeek: Private industrial networks and temporary 5G connectivity islands

16.10.2018 | Event News

5th International Conference on Cellular Materials (CellMAT), Scientific Programme online

02.10.2018 | Event News

 
Latest News

Nanocages in the lab and in the computer: how DNA-based dendrimers transport nanoparticles

19.10.2018 | Life Sciences

Thin films from Braunschweig on the way to Mercury

19.10.2018 | Physics and Astronomy

App-App-Hooray! - Innovative Kits for AR Applications

19.10.2018 | Trade Fair News

VideoLinks
Science & Research
Overview of more VideoLinks >>>