Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

UBC Research Pokes Holes in Hubbard Model, Could Help Solve Enigma of High-Temperature Superconductors

24.08.2009
New UBC research has literally and figuratively poked holes in single-band Hubbard physics--a model that has been used to predict and calculate the behavior of high-temperature superconductors for 20 years.

The findings are the first compelling evidence challenging the model under certain conditions, and could necessitate entirely new theoretical approaches to explaining superconductivity in cuprate materials, one of the outstanding mysteries in condensed-matter physics.

"Single-band Hubbard physics has been used for 20 years to predict how superconducting cuprate materials accommodate the 'holes' left by electron removal," says Darren Peets, lead author of the study who conducted the research while a UBC doctoral student.

"But now it looks like the approaches that underpin a large fraction of the theoretical work in the field just don't work across all the ranges of superconductivity we can study. The part of the cuprates' superconducting phase diagram we looked at could exhibit less-bizarre behaviour, or we could be seeing completely new physics, but in either case the usual theoretical approaches do not work here."

The findings were published today in the journal Physical Review Letters.

Cuprates normally act as insulators but become superconductors when electrons are removed--a process known as 'doping' holes into the material. Physicists consider a material optimally doped when it achieves superconductivity at the highest, most accessible temperature.

UBC researchers where able to break the single-band Hubbard model by 'overdoping' a crystal cuprate superconductor past its optimal range--a level of doping that is difficult to achieve and very rarely studied. While the model explains the material's electron behaviour during doping, Peets and his team found the model falls apart as even more electrons are removed.

"By probing the electronic states using tunable-energy X-rays, we were able to show that this region accommodates electron holes in a fundamentally different manner, and that the interactions among the holes already in the material change completely."

Special crystal samples grown at UBC enabled the team to overdope the superconductor to a degree rarely possible with most materials. "Few materials exist in this doping range, and they tend to be very difficult to grow crystals of," says Peets. "In the case of these crystals, thallium oxide--which is toxic--boils off near growth temperatures if you allow it. So a fair bit of work and care is required."

Discovered in 1986, high-temperature superconductors are cuprates--copper oxides. The materials, which exhibit superconducting properties at usually cold temperatures--often in excess of 90 kelvin--remain an enigma despite intense scrutiny. And because their superconducting state persists at more manageable temperatures, more commercial applications are feasible.

Peets, currently a post-doctoral researcher at Kyoto University, conducted the research at the Berkeley Advanced Light Source synchrotron under the supervision of UBC Physics and Astronomy Professor Douglas Bonn, and with UBC chemist and physicist Professor George Sawatzky.

The work was supported by the Natural Sciences and Engineering Research Council of Canada, the Canada Research Chairs program, the British Columbia Synchrotron Institute, and the Canadian Institute for Advanced Research.

The paper is available online (subscription required):
http://link.aps.org/abstract/PRL/v103/e087402

Chris Balma | EurekAlert!
Further information:
http://www.ubc.ca

More articles from Physics and Astronomy:

nachricht Breakthrough with a chain of gold atoms
17.02.2017 | Universität Konstanz

nachricht New functional principle to generate the „third harmonic“
16.02.2017 | Laser Zentrum Hannover e.V.

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>