Featured Research

from universities, journals, and other organizations

Quantum simulator gives clues about magnetism

Date:
May 15, 2014
Source:
Canadian Institute for Advanced Research
Summary:
Researchers optically trapped a cloud of gas a billion times colder than air in a very low-pressure vacuum, and found a lower speed limit to diffusion. Assembling the puzzles of quantum materials is, in some ways, like dipping a wire hanger into a vat of soapy water, says one of the researchers. Long before mathematical equations could explain the shapes and angles in the soap foams, mathematicians conjectured that soap films naturally found the geometry that minimized surface area, thus solving the problem of minimal surfaces. They could be created simply by blowing soap bubbles.

Pictured is a vacuum system that isolates ultracold atoms from room temperature and pressure. Atoms are suspended in this vacuum with laser beams, and manipulated with magnetic fields. A simple photograph taken with an infrared sensitive camera gives information about the atoms.
Credit: Denzil Green / Canadian Institute for Advanced Research

Assembling the puzzles of quantum materials is, in some ways, like dipping a wire hanger into a vat of soapy water, says CIFAR (Canadian Institute for Advanced Research) Fellow Joseph Thywissen (University of Toronto).

Long before mathematical equations could explain the shapes and angles in the soap foams, mathematicians conjectured that soap films naturally found the geometry that minimized surface area, thus solving the problem of minimal surfaces. They could be created simply by blowing soap bubbles.

At the University of Toronto's Ultracold Atoms Lab, Thywissen and his team strive to answer what he calls "soap bubble" questions -- deep mysteries of the enigmatic quantum materials world that simulations can help us solve. Since the electrons within quantum materials, such as superconductors, zoom far too quickly for careful observation, Thywissen's team uses ultracold gases instead, in this way simulating one quantum system with another, more easily studied, quantum system.

"Simulation gives you the answers but not the theory behind them," says Thywissen.

Thywissen's lab has revealed some of these answers in a new paper about the magnetism and diffusion of atoms in ultracold gases, published in the journal Science. The researchers optically trapped a cloud of gas a billion times colder than air in a very low-pressure vacuum.

They oriented the ultracold atoms, which behave like microscopic magnets, to make them all point in the same direction in space, then manipulated the spins with an effect that's regularly used in hospitals for MRIs, called a spin echo.

Twisting up the direction into a corkscrew pattern and then untwisting it, they measured the strength of interactions between atoms. They observed that at first the atoms did not interact, but one millisecond later they were strongly interacting and correlated.

This rapid change suggested that something was happening to alter the atoms' magnetism as the process unfolded.

"The Pauli Principle forbids identical ultracold atoms from interacting, so we knew something was scrambling the spins at a microscopic level," Thywissen says.

What was happening, the researchers learned next, was diffusion -- the same process that takes place when the smell of perfume fills the air of a room, for example.

"If I open a bottle of perfume in the front of the room, it takes a little while for those particles to diffuse to the back of the room," Thywissen says. "They bump into other particles on the way, but eventually get there. You can imagine that the more particles bump into each other, the slower diffusion occurs."

Cranking up interactions to their maximum allowed level, the Toronto team tried to see how slow diffusion could be. They lowered temperature below a millionth of a degree above absolute zero. You might guess that the speed of diffusion would eventually reach zero, but instead the experiment found a lower limit to diffusion.

"Whereas cars on the freeway need to drive below the speed limit, strongly interacting spins need to diffuse above a quantum speed limit," Thywissen says.

Ultracold atoms are just one of a larger family of strongly interacting materials, that also include superconductors and magnetic materials. Thywissen is a member of the CIFAR Quantum Materials program, which is developing an understanding of these materials' novel properties. Cold atoms offer a promising way to explore the mystery of how electrons self-organize to exhibit unusual and valuable properties, such as superconductivity. Quantum materials contain mysteries that have challenged physicists for decades.

"Our measurements imply a diffusivity bound whose mathematical simplicity is exciting: it hints at a universal principle about spin transport, waiting to be uncovered," he says.


Story Source:

The above story is based on materials provided by Canadian Institute for Advanced Research. Note: Materials may be edited for content and length.


Journal Reference:

  1. A. B. Bardon, S. Beattie, C. Luciuk, W. Cairncross, D. Fine, N. S. Cheng, G. J. A. Edge, E. Taylor, S. Zhang, S. Trotzky, J. H. Thywissen. Transverse Demagnetization Dynamics of a Unitary Fermi Gas. Science, 2014; 344 (6185): 722 DOI: 10.1126/science.1247425

Cite This Page:

Canadian Institute for Advanced Research. "Quantum simulator gives clues about magnetism." ScienceDaily. ScienceDaily, 15 May 2014. <www.sciencedaily.com/releases/2014/05/140515142812.htm>.
Canadian Institute for Advanced Research. (2014, May 15). Quantum simulator gives clues about magnetism. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2014/05/140515142812.htm
Canadian Institute for Advanced Research. "Quantum simulator gives clues about magnetism." ScienceDaily. www.sciencedaily.com/releases/2014/05/140515142812.htm (accessed July 25, 2014).

Share This




More Matter & Energy News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

TSA Administrator on Politics and Flight Bans

TSA Administrator on Politics and Flight Bans

AP (July 24, 2014) TSA administrator, John Pistole's took part in the Aspen Security Forum 2014, where he answered questions on lifting of the ban on flights into Israel's Tel Aviv airport and whether politics played a role in lifting the ban. (July 24) Video provided by AP
Powered by NewsLook.com
Creative Makeovers for Ugly Cellphone Towers

Creative Makeovers for Ugly Cellphone Towers

AP (July 24, 2014) Mobile phone companies and communities across the country are going to new lengths to disguise those unsightly cellphone towers. From a church bell tower to a flagpole, even a pencil, some towers are trying to make a point. (July 24) Video provided by AP
Powered by NewsLook.com
Algonquin Power Goes Activist on Its Target Gas Natural

Algonquin Power Goes Activist on Its Target Gas Natural

TheStreet (July 23, 2014) When The Deal's Amanda Levin exclusively reported that Gas Natural had been talking to potential suitors, the Ohio company responded with a flat denial, claiming its board had not talked to anyone about a possible sale. Lo and behold, Canadian utility Algonquin Power and Utilities not only had approached the company, but it did it three times. Its last offer was for $13 per share as Gas Natural's was trading at a 60-day moving average of about $12.50 per share. Now Algonquin, which has a 4.9% stake in Gas Natural, has taken its case to shareholders, calling on them to back its proposals or, possibly, a change in the target's board. Video provided by TheStreet
Powered by NewsLook.com
Robot Parking Valet Creates Stress-Free Travel

Robot Parking Valet Creates Stress-Free Travel

AP (July 23, 2014) 'Ray' the robotic parking valet at Dusseldorf Airport in Germany lets travelers to avoid the hassle of finding a parking spot before heading to the check-in desk. (July 23) Video provided by AP
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