Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum Simulator Gives Clues About Magnetism

19.05.2014

Science paper reveals new clues about how ultracold atoms interact, including how they can switch from non-interacting to strongly interacting in only a millisecond.

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.

Thywissen says CIFAR’s support helped make this successful experiment possible.

“CIFAR enabled me to assemble a world-class team.”

***
The authors on the paper “Transverse Demagnetization Dynamics of a Unitary Fermi Gas,” published in Science, are Alma Bardon, Scott Beattie, Chris Luciuk, Will Cairncross, Daniel Fine, Nathan Cheng, Graham Edge, Edward Taylor, Shizhong Zhang, Stefan Trotzky and Joseph Thywissen.

About CIFAR

CIFAR brings together extraordinary scholars and scientists from around the world to address questions of global importance. Based in Toronto, Canada, CIFAR is a global research organization comprising nearly 400 fellows, scholars and advisors from more than 100 institutions in 16 countries. The Institute helps to resolve the world’s major challenges by contributing transformative knowledge, acting as a catalyst for change, and developing a new generation of research leaders. Established in 1982, CIFAR partners with the Government of Canada, provincial governments, individuals, foundations, corporations and research institutions to extend our impact in the world.

CIFAR’s program in Quantum Materials invents and explores materials whose novel and unusual electronic properties, like superconductivity, could revolutionize technology.

For more information including images, contact:

Lindsay Jolivet
Writer & Media Relations Specialist
Canadian Institute for Advanced Research
lindsay.jolivet@cifar.ca
416-971-4876

Joseph Thywissen
University of Toronto
jht@physics.utoronto.ca
416-978-2941 (Office)

Dominic Ali | newswise

Further reports about: CIFAR Magnetism Quantum Simulator Toronto diffuse electrons interactions materials microscopic superconductors

More articles from Physics and Astronomy:

nachricht Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics

nachricht What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin

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: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>