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.
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
Gamma rays will reach beyond the limits of light
23.10.2017 | Chalmers University of Technology
Creation of coherent states in molecules by incoherent electrons
23.10.2017 | Tata Institute of Fundamental Research
Salmonellae are dangerous pathogens that enter the body via contaminated food and can cause severe infections. But these bacteria are also known to target...
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
23.10.2017 | Event News
17.10.2017 | Event News
10.10.2017 | Event News
23.10.2017 | Life Sciences
23.10.2017 | Physics and Astronomy
23.10.2017 | Health and Medicine