In Innsbruck, Austria, a team of physicists led by Francesca Ferlaino experimentally observed how the anisotropic properties of particles deform the Fermi surface in a quantum gas. The work published in Science provides the basis for future studies on how the geometry of particle interactions may influence the properties of a quantum system.
How a system behaves is determined by its interaction properties. An important concept in condensed matter physics for describing the energy distribution of electrons in solids is the Fermi surface, named for Italian physicist Enrico Fermi. The existence of the Fermi surface is a direct consequence of the Pauli exclusion principle, which forbids two identical fermions from occupying the same quantum state simultaneously.
Energetically, the Fermi surface divides filled energy levels from the empty ones. For electrons and other fermionic particles with isotropic interactions – identical properties in all directions - the Fermi surface is spherical. “This is the normal case in nature and the basis for many physical phenomena,” says Francesca Ferlaino from the Institute for Experimental Physics at the University of Innsbruck.
“When the particle interaction is anisotropic – meaning directionally dependent – the physical behavior of a system is completely altered. Introducing anisotropic interactions can deform the Fermi surface and it is predicted to assume an ellipsoidal shape.” The deformation of the Fermi surface is caused by the interplay between strong magnetic interaction and the Pauli exclusion principle. Francesca Ferlaino and her experimental research group have now been able to show such a deformation for the first time.
Simulation in ultracold quantum gas
For their experiment, the quantum physicists confined a gas of fermionic erbium atoms in a laser trap and cooled it to almost absolute zero. The element erbium is strongly magnetic, which causes extreme dipolar behavior. The interaction between these atoms is, therefore, directionally dependent. When the physicists release the ultracold gas from the trap, they are able to infer the shape of the Fermi surface from the momentum distribution of the particles.
“Erbium atoms behave similarly to magnets, which means that their interaction is strongly dependent on the direction in which the particles interact. Our experiment shows that the shape of the Fermi surface depends on the geometry of the interaction and is not spherical anymore,” explains first author of the study Kiyotaka Aikawa the phenomenon that is extremely difficult to observe
“The general question we deal with here is how the geometry of particle interactions influences the quantum properties of matter,” explains Francesca Ferlaino. Answering this question is of interest for physicists from different branches of physics such as the study of high-temperature superconductors. “We need a better understanding of these properties to develop new quantum systems,” underlines Francesca Ferlaino. Ultracold quantum gases once more provide an ideal platform for simulating complex scenarios.
This work was financially supported by the Austrian Ministry of Science, the Austrian Science Fund and the European Union. Since July 2014 ERC and START awardee Francesca Ferlaino is Scientific Director at the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences.
Publication: Observation of Fermi surface deformation in a dipolar quantum gas. K. Aikawa,
S. Baier, A. Frisch, M. Mark, C. Ravensbergen, F. Ferlaino. Science 2014
DOI: 10.1126/science.1255259 arXiv:1405.2154 http://arxiv.org/abs/1405.2154
Univ.-Prof. Dr. Francesca Ferlaino
Institute for Experimental Physics
University of Innsbruck
Institute for Quantum Optics and Quantum Information
Austrian Academy of Sciences
6020 Innsbruck, Austria
Phone: +43 512 507-52440 (Lab.: -52441), (Secr.: -52449), (Fax: -2921)
Public Relations office
University of Innsbruck
Phone: +43 512 507 32022
http://dx.doi.org/10.1126/science.1255259 - Observation of Fermi surface deformation in a dipolar quantum gas. K. Aikawa, S. Baier, A. Frisch, M. Mark, C. Ravensbergen, F. Ferlaino. Science 2014
http://www.ultracold.at - Ultracold Atoms and Quantum Gases
Dr. Christian Flatz | Universität Innsbruck
UNH scientists help provide first-ever views of elusive energy explosion
16.11.2018 | University of New Hampshire
NASA keeps watch over space explosions
16.11.2018 | NASA/Goddard Space Flight Center
Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.
Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
16.11.2018 | Health and Medicine
16.11.2018 | Life Sciences
16.11.2018 | Life Sciences