Described in Nature Physics,* the new research lends more support to the idea that JILA studies of superfluidity (flow with zero friction) in atomic gases may help scientists understand far more complicated high-temperature superconductors, solids with zero resistance to electrical current at relatively high temperatures. Known high-temperature superconductors only superconduct well below room temperature, but a detailed understanding of how the materials work may one day lead to practical applications such as more efficient transmission of electricity across power grids.
JILA is operated jointly by the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder.
The JILA group studies how atoms in a Fermi gas** behave as they "cross over" from acting like a Bose Einstein condensate, in which atom pairs form tightly bound molecules, to behaving like pairs of separated electrons in a superconductor. In the new study, JILA scientists applied a technique they developed in 2008 to explore subtle energy properties of ultracold atoms. The technique is an adaptation of photoemission spectroscopy, long used to probe the energy of electrons in materials. A superconductor research group recently used electron photoemission spectroscopy to find evidence of electron pairing above the critical temperature where the material switches from a superconductor to a regular conductor. Why this duality occurs is a subject of debate.
The JILA scientists performed comparable measurements for an ultracold gas of potassium atoms at and above temperatures where superfluidity disappears. Like the superconductor group, the JILA team found evidence of atom pairing above the critical temperature. This demonstrates the existence of a so-called "pseudo-gap region" where the system retains some pairs of correlated fermions but not all characteristics of superfluidity. The findings were made possible in part by significant improvements in the signal strength of the atom photoemission spectroscopy technique since 2008.
"What makes this really interesting is that the two systems are actually very different, with the high-temperature superconductor being much more complicated than atomic gases," says NIST/JILA Fellow Deborah Jin. "The observation of similar behavior with similar measurements suggests that having a pseudogap phase does not require complicated explanations, such as lattice effects, two-dimensionality, or exotic pairing mechanisms."
Co-authors of the new paper are theorists from the Universita di Camerino in Italy. The research was funded by the National Science Foundation.
* J.P. Gaebler, J.T. Stewart, T.E. Drake and D.S. Jin, A. Perali, P. Pieri and G.C. Strinati. 2010. Observation of pseudogap behavior in a strongly interacting Fermi gas. Nature Physics. Posted online July 4.
** A Fermi gas is a collection of noninteracting particles called fermions, one of two categories of fundamental particles found in nature (bosons are the other). Identical fermions cannot occupy the same place at the same time.
Laura Ost | Newswise Science News
A new kind of quantum bits in two dimensions
19.03.2018 | Vienna University of Technology
'Frequency combs' ID chemicals within the mid-infrared spectral region
16.03.2018 | American Institute of Physics
For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.
In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...
Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...
On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...
The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...
At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.
When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...
19.03.2018 | Event News
16.03.2018 | Event News
13.03.2018 | Event News
20.03.2018 | Agricultural and Forestry Science
20.03.2018 | Life Sciences
20.03.2018 | Life Sciences