Featured Research

from universities, journals, and other organizations

Measurements Recast Usual View Of Elusive Force

Date:
February 8, 2007
Source:
National Institute of Standards and Technology
Summary:
Physicists at JILA have demonstrated that the warmer a surface is, the stronger its subtle ability to attract nearby atoms, a finding that could affect the design of devices that rely on small-scale interactions, such as atom chips, nanomachines and microelectromechanical systems.

JILA scientists measured how temperature affects the Casimir-Polder force using an apparatus that holds four small squares of glass inside a vacuum chamber. A cloud of ultracold atoms in a Bose-Einstein Condensate (BEC) was held a few micrometers below one piece of glass, and the force was calculated based on the wiggling of the BEC. Warmer glass magnified the attraction between the surface and the atoms.
Credit: E. Cornell group/JILA

Physicists at JILA have demonstrated that the warmer a surface is, the stronger its subtle ability to attract nearby atoms, a finding that could affect the design of devices that rely on small-scale interactions, such as atom chips, nanomachines, and microelectromechanical systems (MEMS).

The research highlights an underappreciated aspect of the elusive Casimir-Polder force, one of the stranger effects of quantum mechanics. The force arises from the ever-present random fluctuation of microscopic electric fields in empty space. The fluctuations get stronger near a surface, and an isolated neutral atom nearby will feel them as a subtle pull--a flimsy, invisible rubber band between bulk objects and atoms that may be a source of friction, for example, in tiny devices. The JILA group previously made the most precise measurement ever of Casimir-Polder, measuring forces hundreds of times weaker than ever before and at greater distances (more than 5 micrometers). JILA is a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder.

Now, as reported in a paper scheduled for this week's issue of Physical Review Letters, the JILA team has made the first measurement of the temperature dependence of this force. By using a combination of temperatures at opposite extremes--making a glass surface very hot while keeping the environment neutral and using ultracold atoms as a measurement tool--the new research underscores the power of surfaces to influence the Casimir-Polder force. That is, electric fields within the glass mostly reflect inside the surface but also leak out a little bit to greatly strengthen the fluctuations in neighboring space. As a result, says group leader and NIST Fellow Eric Cornell, "warm glass is stickier than cold glass."

The experiments demonstrate the practical use of a Bose-Einstein Condensate (BEC), a form of matter first created at JILA a decade ago. In a BEC, thousands of ultracold atoms coalesce into a "superatom" in a single quantum state. Cornell, who shared the 2001 Nobel Prize in Physics for this development, says the purity and sensitivity of a BEC makes it uniquely useful as a tool for measuring very slight forces and changes.

To measure the Casimir-Polder force, a BEC of about 250,000 rubidium atoms in a magnetic trap was placed a few micrometers from a glass plate. As the BEC was brought closer to the surface, the "wiggling" of the condensate was observed over time. Based on the changes in the oscillation frequency, the researchers calculated the force. In the latest experiment, measurements were made as a laser beam was used to heat the glass plate from room temperature (about 37 degrees C or 98 degrees F) to very hot (about 330 degrees C or 630 degrees F), while the surrounding environment was kept near room temperature. The strength of the force was shown to be nearly three times larger when the glass temperature doubled. The researchers also were able to separate the forces emanating from the surface versus the environment.

The research is supported in part by the National Science Foundation. The JILA group collaborated with theorists from the University of Trento, Italy.

* J.M. Obrecht, R.J. Wild, M. Antezza, L.P. Pitaevskii, S. Stringari and E.A. Cornell. Measurement of the temperature dependence of the Casimir-Polder force. Physical Review Letters. Vol. 98, No. 6, Feb. 9, 2007.


Story Source:

The above story is based on materials provided by National Institute of Standards and Technology. Note: Materials may be edited for content and length.


Cite This Page:

National Institute of Standards and Technology. "Measurements Recast Usual View Of Elusive Force." ScienceDaily. ScienceDaily, 8 February 2007. <www.sciencedaily.com/releases/2007/02/070207171736.htm>.
National Institute of Standards and Technology. (2007, February 8). Measurements Recast Usual View Of Elusive Force. ScienceDaily. Retrieved April 20, 2014 from www.sciencedaily.com/releases/2007/02/070207171736.htm
National Institute of Standards and Technology. "Measurements Recast Usual View Of Elusive Force." ScienceDaily. www.sciencedaily.com/releases/2007/02/070207171736.htm (accessed April 20, 2014).

Share This



More Matter & Energy News

Sunday, April 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Why Did Nike Fire Most Of Its Nike FuelBand Team?

Why Did Nike Fire Most Of Its Nike FuelBand Team?

Newsy (Apr. 19, 2014) Nike fired most of its Digital Sport hardware team, the group behind Nike's FuelBand device. Could Apple or an overcrowded market be behind layoffs? Video provided by Newsy
Powered by NewsLook.com
Small Reactors Could Be Future of Nuclear Energy

Small Reactors Could Be Future of Nuclear Energy

AP (Apr. 17, 2014) After the Fukushima nuclear disaster, the industry fell under intense scrutiny. Now, small underground nuclear power plants are being considered as the possible future of the nuclear energy. (April 17) Video provided by AP
Powered by NewsLook.com
Horseless Carriage Introduced at NY Auto Show

Horseless Carriage Introduced at NY Auto Show

AP (Apr. 17, 2014) An electric car that proponents hope will replace horse-drawn carriages in New York City has also been revealed at the auto show. (Apr. 17) Video provided by AP
Powered by NewsLook.com
Honda's New ASIMO Robot, More Human-Like Than Ever

Honda's New ASIMO Robot, More Human-Like Than Ever

AFP (Apr. 17, 2014) It walks and runs, even up and down stairs. It can open a bottle and serve a drink, and politely tries to shake hands with a stranger. Meet the latest ASIMO, Honda's humanoid robot. Duration: 00:54 Video provided by AFP
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