Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Supersonic waves may help electronics beat the heat

18.05.2018

Researchers at the Department of Energy's Oak Ridge National Laboratory made the first observations of waves of atomic rearrangements, known as phasons, propagating supersonically through a vibrating crystal lattice--a discovery that may dramatically improve heat transport in insulators and enable new strategies for heat management in future electronics devices.

"The discovery gives you a different way to control the flow of heat," said lead author Michael Manley of the paper published in Nature Communications. "It provides a shortcut through the material--a way to send the energy of pure atomic motion at a speed that's higher than you can with phonons [atomic vibrations].


Neutron scattering studies of lattice excitations in a fresnoite crystal revealed a way to speed thermal conduction.

Credit: Oak Ridge National Laboratory, US Dept. of Energy; graphic artist Jill Hemman

This shortcut may open possibilities in heat management of nanoscale materials. Imagine the possibility of a thermal circuit breaker, for example."

The scientists used neutron scattering to measure phasons with velocities about 2.8 times and about 4.3 times faster than the natural "speed limits" of longitudinal and transverse acoustic waves, respectively. "We didn't expect them to be going that fast without [fading]," Manley said.

Insulators are necessary in electronic devices to prevent short circuits; but without free electrons, thermal transport is limited to the energy of atomic motion. Hence, understanding the transport of heat by atomic motion in insulators is important.

The researchers scattered neutrons in fresnoite, a crystalline mineral so named because it was first found in Fresno, California. It is promising for sensor applications through its piezoelectric property, which allows it to turn mechanical stress into electrical fields.

Fresnoite has a flexible framework structure that develops a competing order in the structure that does not match the underlying crystal order, like an overlay of mismatched tiles. Phasons are excitations associated with atomic rearrangements in the crystal that change the phase of waves describing the mismatch in the structure.

Phase differences accumulate in a lattice of wrinkles--called solitons. Solitons are solitary waves that propagate with little loss of energy and retain their shape. They can also warp the local environment in a way that allows them to travel faster than sound.

"The soliton is a very deformed region in the crystal where the displacements of the atoms are large and the force-displacement relationship is no longer linear," Manley said. "The material stiffness is locally enhanced within the soliton, leading to a faster energy transfer."

Raffi Sahul of Meggitt Sensing Systems of Irvine, California, grew a single crystal of fresnoite and sent it to ORNL for neutron scattering experiments that Manley conceived to characterize how energy moved through the crystal. "Neutrons are the best way to study this because their wavelengths and energies are in a sense matched to the atomic vibrations," Manley said.

Manley performed measurements with Paul Stonaha, Doug Abernathy and John Budai using time-of-?ight neutron scattering at the Spallation Neutron Source, and with Stonaha, Songxue Chi, and Raphael Hermann using triple-axis neutron scattering at the High Flux Isotope Reactor.

At SNS, the scientists started with a pulsed source of neutrons of different energies and used the ARCS instrument, which selects neutrons in a narrow energy range and scatters them off a sample so detectors can map the energy and momentum transfer over a wide range.

"The large measurement area was important to this study because the features weren't where you would normally expect them to be," said Abernathy. "This gives the neutron measurements a great chance to determine the velocities of the propagating phasons, calculated from the slope of their dispersion curves."

Dispersion is the relationship between the wavelength and the energy that characterizes a propagating wave.

"Once the SNS measurements told us where to look, we used triple-axis spectrometry at HFIR, which provided a constant flux of neutrons, to focus on that one point," Manley said. "A unique thing about Oak Ridge National Laboratory is that we have both a world-class spallation source and a world-class reactor source for neutron research. We can go back and forth between facilities and really get a comprehensive view of things."

Next the researchers will explore other crystals that, like fresnoite, can rotate phasons. Strain applied with an electric field may be able to change the rotation. Changes in temperature may vary properties too.

The title of the paper is "Supersonic propagation of lattice energy by phasons in fresnoite."

###

The research used resources at SNS and HFIR, DOE Office of Science User Facilities at ORNL. Funding came from the DOE Office of Science.

UT-Battelle manages ORNL for DOE's Office of Science. The single largest supporter of basic research in the physical sciences in the United States, the Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit https://science.energy.gov/. --by Dawn Levy

Media Contact

Dawn Levy
levyd@ornl.gov
865-576-6448

 @ORNL

http://www.ornl.gov 

Dawn Levy | EurekAlert!

More articles from Power and Electrical Engineering:

nachricht Fraunhofer starts development of refrigerant-free, energy-efficient electrocaloric heat pumps
09.12.2019 | Fraunhofer IPM

nachricht A solution for cleaning up PFAS, one of the world's most intractable pollutants
06.12.2019 | Colorado State University

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Cheers! Maxwell's electromagnetism extended to smaller scales

More than one hundred and fifty years have passed since the publication of James Clerk Maxwell's "A Dynamical Theory of the Electromagnetic Field" (1865). What would our lives be without this publication?

It is difficult to imagine, as this treatise revolutionized our fundamental understanding of electric fields, magnetic fields, and light. The twenty original...

Im Focus: Highly charged ion paves the way towards new physics

In a joint experimental and theoretical work performed at the Heidelberg Max Planck Institute for Nuclear Physics, an international team of physicists detected for the first time an orbital crossing in the highly charged ion Pr⁹⁺. Optical spectra were recorded employing an electron beam ion trap and analysed with the aid of atomic structure calculations. A proposed nHz-wide transition has been identified and its energy was determined with high precision. Theory predicts a very high sensitivity to new physics and extremely low susceptibility to external perturbations for this “clock line” making it a unique candidate for proposed precision studies.

Laser spectroscopy of neutral atoms and singly charged ions has reached astonishing precision by merit of a chain of technological advances during the past...

Im Focus: Ultrafast stimulated emission microscopy of single nanocrystals in Science

The ability to investigate the dynamics of single particle at the nano-scale and femtosecond level remained an unfathomed dream for years. It was not until the dawn of the 21st century that nanotechnology and femtoscience gradually merged together and the first ultrafast microscopy of individual quantum dots (QDs) and molecules was accomplished.

Ultrafast microscopy studies entirely rely on detecting nanoparticles or single molecules with luminescence techniques, which require efficient emitters to...

Im Focus: How to induce magnetism in graphene

Graphene, a two-dimensional structure made of carbon, is a material with excellent mechanical, electronic and optical properties. However, it did not seem suitable for magnetic applications. Together with international partners, Empa researchers have now succeeded in synthesizing a unique nanographene predicted in the 1970s, which conclusively demonstrates that carbon in very specific forms has magnetic properties that could permit future spintronic applications. The results have just been published in the renowned journal Nature Nanotechnology.

Depending on the shape and orientation of their edges, graphene nanostructures (also known as nanographenes) can have very different properties – for example,...

Im Focus: Electronic map reveals 'rules of the road' in superconductor

Band structure map exposes iron selenide's enigmatic electronic signature

Using a clever technique that causes unruly crystals of iron selenide to snap into alignment, Rice University physicists have drawn a detailed map that reveals...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

The Future of Work

03.12.2019 | Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

 
Latest News

Weizmann physicists image electrons flowing like water

12.12.2019 | Physics and Astronomy

Revealing the physics of the Sun with Parker Solar Probe

12.12.2019 | Physics and Astronomy

New technique to determine protein structures may solve biomedical puzzles

12.12.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>