Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Spinons - Confined like Quarks

30.11.2009
Phenomenon known from Particle Theory observed for the first time in Condensed Matter

The concept of confinement is one of the central ideas in modern physics. The most famous example is that of quarks which bind together to form protons and neutrons. Now Prof. Bella Lake from Helmholtz-Zentrum Berlin together with an international team of scientists report for the first time an experimental realization and a proof of confinement phenomenon observed in a condensed matter system.

The concept of confinement states that in certain systems the constituent particles are bound together by an interaction whose strength increases with increasing particle separation. In the case of quarks they are held together by the so called strong force, a force that grows stronger with increasing distance. As a consequence individual particles like quarks don't exist in a free state and their properties can be observed only indirectly.

In the 1990s Prof Alexei Tsvelik from Brookhaven National Laboratory (USA) and co-workers predicted an analogous confinement process in systems known as spin-ladders found in condensed matter physics. Experimental confirmation of this phenomenon has however only been achieved recently as described by Bella Lake et al in the current issue of the journal Nature Physics.

Spin-ladders consist of two chains of copper oxide chemically bonded together. This makes the electrons interact strongly with each other. A remarkable feature of a single chain is that the individual electrons, which behave as an elementary charge combined with magnetic spin, co-operate in concert to separate into independent spin and charge parts. Ac-cording to Bella Lake "The spin parts, known as spinons, have different properties to those of the original electrons. In fact they are analogous to quarks, the building blocks of protons and neutrons." On coupling two chains together to form a spin ladder the spin parts are found to recombine, but in a new way. "We have found, that excitations of individual chains, so called spinons, are confined in a similar way to that in which elementary quarks are held together", Bella Lake said.

The team of scientists have found evidence for the confinement idea by neutron scattering experiments on magnetic crystals of calcium cuprate (a copper-oxide material synthesized at the Leibniz Institute for Solid State and materials research in Dresden). The neutron experiments were performed using the MAPS spectrometer at the ISIS pulsed neutron source at Rutherford Appleton Laboratory, UK. Further the crystal and magnetic structure were investigated from neutron data collected on the E5 instrument at the research reactor BER II in Berlin.

The neutron scattering data show that the electrons essentially first split into spins and charges on the chains, then the spinons pair up again due to ladder effects. Prof Alan Tennant, the head of "Institute Complex Magnetic Materials" at HZB, explained: "The geometry of the ladder in fact plays a special role: the spinons always appear in pairs and when they move apart, they force a reorganisation of the intervening electrons that costs energy. The energy cost grows with separation - like a rubber band." According to Bella Lake "This strong pairing up of two spinons is like quarks binding together to form subatomic particles like hadrons and mesons."

Prof Alexei Tsvelik who developed the theoretical description explained "The formation of hadrons is well established on a qualitative level, but its quantitative aspects remain unresolved. It is unknown how to relate the theoretical parameters to the observed hadron masses. This is one of the reasons why condensed matter analogues are interesting. They provide examples of confinement for which detailed descriptions have been achieved."

Artikel in Nature Physics, DOI: 10.1038/NPHYS1462

Confinement of fractional quantum number particles in a condensed-matter system
Bella Lake, Alexei M. Tsvelik, Susanne Notbohm, D. Alan Tennant, Toby G. Perring, Manfred Reehuis, Chinna-thambi Sekar, Gernot Krabbes and Bernd Büchner

Berlin, den 25. 11.2009

Further informations:
Helmholtz-Zentrum Berlin
Hahn-Meitner-Platz 1
14109 Berlin
Prof. Bella Lake
Head of Junior Research Group
Magnetism an Superconductivity
Tel.: +49/30-8062-2058
bella.lake@helmholtz-berlin.de
Prof. Alan Tennant
Head of Institute Complex
Magnetic Materials
Tel.: +49/30-8062-2741
tennant@helmholtz-berlin.de
Press Office:
Dr. Ina Helms
Tel.: +49/30-8062-2034
ina.helms@helmholtz-berlin.de

Britta Heidrich | Helmholtz-Zentrum
Further information:
http://www.helmholtz-berlin.de/index_en.html

More articles from Physics and Astronomy:

nachricht From rocks in Colorado, evidence of a 'chaotic solar system'
23.02.2017 | University of Wisconsin-Madison

nachricht Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science

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

From rocks in Colorado, evidence of a 'chaotic solar system'

23.02.2017 | Physics and Astronomy

'Quartz' crystals at the Earth's core power its magnetic field

23.02.2017 | Earth Sciences

Antimicrobial substances identified in Komodo dragon blood

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>