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
OU-led team discovers rare, newborn tri-star system using ALMA
27.10.2016 | University of Oklahoma
First results of NSTX-U research operations
26.10.2016 | DOE/Princeton Plasma Physics Laboratory
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
27.10.2016 | Life Sciences
27.10.2016 | Life Sciences
27.10.2016 | Power and Electrical Engineering