Featured Research

from universities, journals, and other organizations

Exotic quantum spin-liquid simulated: A starting point for superconductivity?

Date:
April 11, 2010
Source:
University of Stuttgart
Summary:
An exotic state of matter that physicists call a "quantum spin-liquid" can be realized by electrons in a honeycomb crystal structure, researchers in Germany report.

The simulation of the quantum spin-liquid was performed on a flat honeycomb structure, where the electrons show a dynamical phase lacking any order.
Credit: Image courtesy of University of Stuttgart

An exotic state of matter that physicists call a "quantum spin-liquid" can be realized by electrons in a honeycomb crystal structure.

This is shown by scientists from the Universities of Stuttgart and Würzburg, Germany in a new study published in the journal Nature.

Electrons inside a crystal exist in different states. In many cases it is the crystal structure that decides, if the material is a metal with a finite electric conductivity, or if it is an insulator, which does not carry an electric current. But there also exist insulating materials, whose crystal structures suggest that they should behave like metals. Such materials are called "Mott insulators," and it is the repulsion between the electrons, that suppresses a metallic behaviour, such that the electrons are locked to the atoms.

Such localized electrons tend to order upon lowering the temperature, such as for example in magnetic structures. A "quantum spin-liquid" however is a non-magnetic Mott-insulator that is stabilized purely by quantum mechanical effects. The electrons inside a quantum spin-liquid resist to order down to the lowest temperatures, way down to the absolute zero of temperature at minus 273 degrees Celsius. The tendency to order is suppressed by dynamical fluctuations of the electrons even at zero absolute temperature (quantum fluctuations). For this to happen, the quantum fluctuations must be sufficiently large, which is rarely the case in nature, and also hard to realize in realistic models.

Now theorists from Stuttgart University, Zi Yang Meng, Priv.-Doz. Stefan Wessel, and Prof. Alejandro Muramatsu, together with their colleges Thomas Lang and Prof. Fakher Assaad from Würzburg University, showed that such a quantum spin-liquid exists in a realistic model of interacting electrons. For their study, they used large-scale computer simulations, in order to account for both the interactions between the electrons and their quantum fluctuations. Their unexpected findings were thus accepted for publication in the "Nature" magazine.

The quantum spin-liquid found by Meng et al. occurs in materials where the atoms form a two-dimensional, periodic array of hexagons, thus realizing a honeycomb lattice. Such a crystal structre is found for example in Graphene, a two-dimensional carbon allotrope, that was only recently synthesized, and has since then been the focus of intensive research. If the electronic interactions could be enhanced in such a material, then the highly interesting quantum spin-liquid state could be realized. It appears unlikly that this can be achieved, for example by expansion, in Graphene. Thus, the physicists from Stuttgart and Würzburg suggest exploring honeycomb-like structures formed from other group IV elements that show enhanced electronic interactions. A first step in this direction might already have been taken, since previously chemist succeeded in synthesizing Graphene-like structures of silicon atoms.

Furthermore, the quantum spin-liquid should also be realizable using ultra-cold atoms. In fact, the mathematical model studied by the physicists describes both interacting electrons in solid state systems as well as interacting ultra-cold atoms in an optical lattice. The impressive progress that has been achieved in this research field opens up the possibility to realize the quantum spin-liquid with ultra-cold atoms.

Another fascinating aspect of the quantum spin-liquid is that it can also be viewed as a starting point for superconductivity. Electric currents would then flow without resistance through the material. This has potential for many applications, such as ultra fast computers or the dissipation free transport of electricity.

In their fundamental research, the two theory groups in Stuttgart and Würzburg analyse complex phases of strongly interacting quantum many-body systems in general. They discovered the quantum spin-liquid phase, while studying possible transitions between metallic and insulating phases in a model for Graphene. In the vicinity of such transitions, the quantum fluctuations become significantly enhanced, and destroy any magnetic order. The scientists could also exclude other types of electronic orders from an extensive analysis. Such a study was only possible with the help of modern supercomputers. In particular, for their calculations, the theorists could profit from the highly efficient supercomputer centers in Jülich, München and Stuttgart. For the future, they hope to apply simulations of strongly interacting electrons also to the design of novel materials that realize exotic states of matter -- including the quantum spin-liquid.

The research described above is embedded within the general research activities of the two universities. At the University of Stuttgart, the DFG research unit SFB/TRR 21, "Controll of Quantum Correlations in Tailored Matter," focuses on the realization of tailored quantum systems. Its spokesperson is Prof. Tilmann Pfau from the University of Stuttgart. At the University of Würzburg, a recently established research group "Electron Correlation-Induced Phenomena in Surfaces and Interfaces with Tuneable Interactions" complex electronic states are of central focus. Its spokesperson is Prof. Ralph Claessen from Würzburg University.


Story Source:

The above story is based on materials provided by University of Stuttgart. Note: Materials may be edited for content and length.


Journal Reference:

  1. Z. Y. Meng, T. C. Lang, S. Wessel, F. F. Assaad, A. Muramatsu. Quantum spin liquid emerging in two-dimensional correlated Dirac fermions. Nature, 2010; 464 (7290): 847 DOI: 10.1038/nature08942

Cite This Page:

University of Stuttgart. "Exotic quantum spin-liquid simulated: A starting point for superconductivity?." ScienceDaily. ScienceDaily, 11 April 2010. <www.sciencedaily.com/releases/2010/04/100408141208.htm>.
University of Stuttgart. (2010, April 11). Exotic quantum spin-liquid simulated: A starting point for superconductivity?. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/2010/04/100408141208.htm
University of Stuttgart. "Exotic quantum spin-liquid simulated: A starting point for superconductivity?." ScienceDaily. www.sciencedaily.com/releases/2010/04/100408141208.htm (accessed July 23, 2014).

Share This




More Matter & Energy News

Wednesday, July 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Government Approves East Coast Oil Exploration

Government Approves East Coast Oil Exploration

AP (July 18, 2014) — The Obama administration approved the use of sonic cannons to discover deposits under the ocean floor by shooting sound waves 100 times louder than a jet engine through waters shared by endangered whales and turtles. (July 18) Video provided by AP
Powered by NewsLook.com
Sunken German U-Boat Clearly Visible For First Time

Sunken German U-Boat Clearly Visible For First Time

Newsy (July 18, 2014) — The wreckage of the German submarine U-166 has become clearly visible for the first time since it was discovered in 2001. Video provided by Newsy
Powered by NewsLook.com
Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Reuters - US Online Video (July 17, 2014) — President Barak Obama stopped by at a lunch counter in Delaware before making remarks about boosting the nation's infrastructure. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com
Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

TheStreet (July 16, 2014) — Oil Futures are bouncing back after tumbling below $100 a barrel for the first time since May yesterday. Jeff Grossman is the president of BRG Brokerage and trades at the NYMEX. Grossman tells TheStreet the Middle East is always a concern for oil traders. Oil prices were pushed down in recent weeks on Libya increasing its production. Supply disruptions in Iraq fading also contributed to prices falling. News from China's economic front showing a growth for the second quarter also calmed fears on its slowdown. Jeff Grossman talks to TheStreet's Susannah Lee on this and more on the Energy Department's Energy Information Administration (EIA) report. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins