Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Observation of Second Sound in a Quantum Gas

16.05.2013
Second sound is a quantum mechanical phenomenon, which has been observed only in superfluid helium.

Physicists from the University of Innsbruck, Austria, in collaboration with colleagues from the University of Trento, Italy, have now proven the propagation of such a temperature wave in a quantum gas. The scientists have published their historic findings in the journal Nature.


The cigar-shaped particle cloud is locally heated with a power-modulated laser beam (green).
IQOQI/Ritsch

Below a critical temperature, certain fluids become superfluid and lose internal friction. In addition, fluids in this state conduct heat extremely efficiently, with energy transport occurring in a distinct temperature wave. Because of the similarities to a sound wave, this temperature wave is also called second sound. To explain the nature of superfluids, the famous physicist Lev Landau developed the theory of two-fluid hydrodynamics in Moscow in 1941.

He assumed that fluids at these low temperatures comprise a superfluid and a normal component, whereby the latter one gradually disappears with decreasing temperature. Until now superfluidity has experimentally been observed only in liquid helium and in ultracold quantum gases. Another example of a superfluid system is a neutron star, and evidence also been found in the atomic nucleus.

Superfluidity is closely connected to the technologically important superconductivity, the phenomenon of zero electrical resistance at very low temperatures.

Observation of temperature waves

Ultracold quantum gases are ideal model systems to experimentally observe quantum mechanical phenomena such as superfluidity. In these experiments hundreds of thousands of atoms are cooled in a vacuum chamber to almost absolute zero (−273.15 °C). By using lasers the particles in this state can be controlled and manipulated efficiently and with high accuracy. “Despite intensive research in this field for over ten years now, the phenomenon of second sound has proven elusive for detection in quantum gases,” says Rudolf Grimm from the Institute of Experimental Physics at the University of Innsbruck and the Institute of Quantum Optics and Quantum Information at the Austrian Academy of Sciences. “However, in the end it was amazingly easy to prove.”
In the laboratory, Grimm’s team of quantum physicists prepared a quantum gas consisting of about 300,000 lithium atoms. They heated the cigar-shaped particle cloud locally with a power-modulated laser beam and then observed the propagating temperature wave. “While in superfluid helium only one entropy wave is generated, our Fermi gas also exhibited some thermal expansion and, thus, a measurable density wave,” explains Grimm the crucial difference. It was also the first time that the Innsbruck physicists were able to measure the superfluid fraction in the quantum gas. “Before us nobody had been able to achieve this, which closes a fundamental gap in the research of Fermi gases,” says Rudolf Grimm.

Confirming a theory after 50 years

The research work, published now in the journal Nature, is the result of a long-term close collaboration between the physicists in Innsbruck and the Italian scientists. The theoretical physicists from the Trento Bose-Einstein Condensation Center led by Sandro Stringari and Lev Pitaevskii adapted Lev Landau‘s theory of the description of second sound for the almost one-dimensional geometry of the Innsbruck experiments. Actually Lev Pitaevskii was one of Lev Landau‘s pupils. “With this model it became easy to interpret the results of our measurement,” says Rudolf Grimm. “Moreover, our colleagues from Trento intensely supported our experiment conceptually. The results represent the pinnacle of the collaboration with our partner university in Trento and it is a vital indication for research cooperation within the European Region the Tyrol-South Tyrol-Trentino.” In June the University of Innsbruck will award an Honorary Doctorate to Lev Pitaevskii for his close collaboration with the local scientists.

The scientists are supported by the Austrian Science Fund (FWF) and the European Research Council (ERC).

Publication: Second sound and the superfluid fraction in a Fermi gas with resonant interactions. Leonid A. Sidorenkov, Meng Khoon Tey, Rudolf Grimm, Yan-Hua Hou, Lev Pitaevskii, Sandro Stringari. Advance Online Publication, Nature on May 15, 2013 DOI: 10.1038/nature12136
Contact
Univ.-Prof. Dr. Rudolf Grimm
Institute of 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
mobile: +43 676 872532022
email: christian.flatz@uibk.ac.at
Weitere Informationen:
http://dx.doi.org/10.1038/nature12136
- Second sound and the superfluid fraction in a Fermi gas with resonant interactions. Leonid A. Sidorenkov, Meng Khoon Tey, Rudolf Grimm, Yan-Hua Hou, Lev Pitaevskii, Sandro Stringari. Advance Online Publication, Nature on May 15

http://www.ultracold.at - Research group of Rudolf Grimm

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

More articles from Physics and Astronomy:

nachricht Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst

nachricht Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center

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: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>