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 Astrophysicists explain the mysterious behavior of cosmic rays
18.08.2017 | Moscow Institute of Physics and Technology

nachricht Mars 2020 mission to use smart methods to seek signs of past life
17.08.2017 | Goldschmidt Conference

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

New gene catalog of ocean microbiome reveals surprises

18.08.2017 | Life Sciences

Astrophysicists explain the mysterious behavior of cosmic rays

18.08.2017 | Physics and Astronomy

AI implications: Engineer's model lays groundwork for machine-learning device

18.08.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>