Featured Research

from universities, journals, and other organizations

Quantum Effects Writ Large: Evidence Points To Quantum Nature Of Large-scale Effects

Date:
February 16, 2007
Source:
Rice University
Summary:
A team of physicists from Rice University, Rutgers University, and the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany, reports this week in the journal Science the discovery of surprising quantum effects in a member of a broad class of materials that include high-temperature superconductors and quantum magnets. The effects were observed at a "quantum critical point," a tipping point at which the quantum properties of the material undergo a radical change.

A team of physicists from Rice University, Rutgers University, and the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany, this week reports in the journal Science the discovery of surprising quantum effects in a member of a broad class of materials that include high-temperature superconductors and quantum magnets. The effects were observed in a compound that was cooled nearly to absolute zero, a temperature low enough to bring about a "quantum critical point," a tipping point at which the quantum properties of the material undergo a radical change.

"Physicists have long held that the macroscopic properties of a material at a quantum critical point are completely described in terms of fluctuations of a classical variable called the order parameter," said Rice University theoretical physicist Qimiao Si. "Our results show instead that inherently quantum effects play an important role, and that these can be seen in thermodynamic measurements."

In this week's paper, researchers reported finding telltale signs of a link between quantum effects and thermodynamic properties in the "heavy fermion" compound YbRh2Si2 (YRS) containing the elements ytterbium, rhodium and silicon. This material contains a quantum critical point that separates a magnetic phase from a non-magnetic one.

"Quantum criticality epitomizes the collective organization of a large number of microscopic particles in matter," said Rutgers theorist Elihu Abrahams. "The new research sheds light on such a collective state of strongly interacting electron systems."

The frontier of research in condensed matter physics that is involved centers on the way that quantum effects influence the physical properties of chunks of material containing many billions of billions of atoms. The 1986 discovery of high-temperature superconductivity in copper-oxide ceramics led condensed matter theorists to realize that quantum effects of strongly correlated electron systems are much more complex than have been anticipated in textbook descriptions. One effect whose importance has been increasingly recognized over the past few years is quantum criticality.

Phase transitions, such as water vaporizing or melting, typically occur as a result of temperature change. Quantum phase transitions, by contrast, arise when the forces of quantum mechanics drive a macroscopic material from one type of order to another. A quantum critical point describes the material at the cusp of such a transition.

A quantum critical point occurs at the absolute zero of temperature, which cannot be reached experimentally. However, the effects of quantum phase transitions can be seen in the laboratory at sufficiently low temperatures. In the case at hand, a group of experimentalists at the Max Planck Institute of Chemical Physics of Solids in Dresden made exquisite measurements at very low temperatures of the properties of the metallic YRS that show a quantum phase transition between a magnetic and a non-magnetic state. The Dresden group included Philipp Gegenwart, now at the First Physics Institute (Goettingen), Silke Paschen, now at the Institute of Solid State Physics (TU Vienna), Yoshi Tokiwa, now at Los Alamos National Laboratory (New Mexico), Cornelius Krellner, Tanya Westerkamp, Christoph Geibel, and Institute Director Frank Steglich.

"YRS is uniquely suited for our study, because it is a prototypical quantum critical material that has been well characterized," Steglich said.

Usually, phase transitions are governed by the behavior of a macroscopic variable, the order parameter. In the case of the liquid to vapor transition mentioned above, the density is the order parameter. For a quantum phase transition, an energy scale describes the energy cost to nucleate a domain with a finite order parameter in the state without that order. This energy scale, believed to be the only relevant one by conventional wisdom, describes the fluctuations of the order parameter. The paper reports the measurements of two thermodynamic properties -- magnetization and magnetostriction, or the change in volume as a function of change in magnetic field -- as the material was cooled to near absolute zero.

"Our measurements revealed that a second thermodynamic energy scale exists in the YRS compound," said Philipp Gegenwart. "This additional energy scale goes beyond the theory based on fluctuations of the order parameter."

One possible explanation for this additional energy scale invokes the destruction of a quantum effect, called entanglement, at the quantum critical point. Another ascribes it to the effective disintegration of an electron into separated spin and charge carrying objects, or excitations. Regardless of the final theory, the results reported in the paper bolster the growing body of evidence for the vital role of quantum fluctuations in strongly correlated materials.

The research was supported by the National Science Foundation, the Robert A. Welch Foundation and the Fonds der Chemischen Industrie.


Story Source:

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


Cite This Page:

Rice University. "Quantum Effects Writ Large: Evidence Points To Quantum Nature Of Large-scale Effects." ScienceDaily. ScienceDaily, 16 February 2007. <www.sciencedaily.com/releases/2007/02/070215144253.htm>.
Rice University. (2007, February 16). Quantum Effects Writ Large: Evidence Points To Quantum Nature Of Large-scale Effects. ScienceDaily. Retrieved September 18, 2014 from www.sciencedaily.com/releases/2007/02/070215144253.htm
Rice University. "Quantum Effects Writ Large: Evidence Points To Quantum Nature Of Large-scale Effects." ScienceDaily. www.sciencedaily.com/releases/2007/02/070215144253.htm (accessed September 18, 2014).

Share This



More Matter & Energy News

Thursday, September 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Virtual Reality Headsets Unveiled at Tokyo Game Show

Virtual Reality Headsets Unveiled at Tokyo Game Show

AFP (Sep. 18, 2014) Several companies unveiled virtual reality headsets at the Tokyo Game Show, Asia's largest digital entertainment exhibition. Duration: 00:48 Video provided by AFP
Powered by NewsLook.com
Stocks Hit All-Time High as Fed Holds Steady

Stocks Hit All-Time High as Fed Holds Steady

AP (Sep. 17, 2014) The Federal Reserve signaled Wednesday that it plans to keep a key interest rate at a record low because a broad range of U.S. economic measures remain subpar. Stocks hit an all-time high on the news. (Sept. 17) Video provided by AP
Powered by NewsLook.com
Space Race Pits Bezos Vs Musk

Space Race Pits Bezos Vs Musk

Reuters - Business Video Online (Sep. 16, 2014) Amazon CEO Jeff Bezos' startup will team up with Boeing and Lockheed to develop rocket engines as Elon Musk races to have his rockets certified. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
MIT's Robot Cheetah Unleashed — Can Now Run, Jump Freely

MIT's Robot Cheetah Unleashed — Can Now Run, Jump Freely

Newsy (Sep. 16, 2014) MIT developed a robot modeled after a cheetah. It can run up to speeds of 10 mph, though researchers estimate it will eventually reach 30 mph. Video provided by Newsy
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