(Press-News.org) Contact information: Lynn Yarris
lcyarris@lbl.gov
510-486-5375
DOE/Lawrence Berkeley National Laboratory
Crossover sound
Unambiguous evidence for coherent phonons in superlattices
We all learn in high school science about the dual nature of light - that it exists as both waves and quantum particles called photons. It is this duality of light that enables the coherent transport of photons in lasers. Sound at the atomic-scale has the same dual nature, existing as both waves and quasi-particles known as phonons. Does this duality allow for phonon-based lasers? Some theorists say yes, but the point has been argued for years. Recently a large collaboration, in which Berkeley Lab scientists played a prominent role, provided the first "unambiguous demonstration" of the coherent transport of phonons.
Ramamoorthy Ramesh, a senior scientist with Berkeley Lab's Materials Sciences Division, was a co-leader with Arun Majumdar, a former Associated Laboratory director at Berkeley Lab and
and currently VP for Energy at Google, of an experiment in which phonons underwent particle-to-wave crossovers in superlattices of perovskite oxides.
"Our observations open up new opportunities for studying the wave-like nature of phonons, particularly phonon interference effects," says Ramesh. "Such research should have potential applications in thermoelectrics and thermal management, and in the long run could help the development of phonon lasers."
Unlike elementary particles such as electrons and photons, whose wave nature and coherent properties are well-established, experimental demonstration of coherent wave-like properties of phonons has been limited. This is because phonons are not true particles, but the collective vibrations of atoms in a crystal lattice that can be quantized as if they were particles. However, understanding the coherent wave nature of phonons is of fundamental importance to thermoelectrics, materials that can convert heat into electricity, or electricity into heat, which represent a potentially huge source of clean, green energy.
"Lower thermal conductivity is one of the keys to improving the efficiency of thermoelectric materials and the key to thermal conductivity in semiconductors is phonon transport," Majumdar says. "Nanostructures such as superlattices are the ideal model systems for the study of phonon transport, particularly the wave-particle crossover, because the wavelength of the most relevant phonons are in the range of one to 10 nanometers."
Superlattices are artificial periodic structures consisting of two dissimilar semiconductors in alternating layers a few nanometers thick. For this demonstration, the collaboration synthesized high-quality superlattices of electrically insulating perovskite oxides on various single-crystal oxide substrates. Interface densities in these superlattices were
systematically varied using two different epitaxial growth techniques. Thermal conductivity was measured as a function of interface density.
"Our results were in general agreement with theoretical predictions of crossover from incoherent particle-like to coherent wave-like phonon transport," Ramesh says. "We also found sufficient evidence to eliminate extraneous or spurious effects, which could have alternatively explained the observed thermal conductivity minimum in these superlattices."
Capitalizing on the wave behavior of phonons should enable new advances in new heat transfer applications, the collaborators say. Furthermore, perovskite superlattice-based heterostructures could also serve as basic building blocks for the development of lasers in which beams of coherent phonons rather than coherent photons are emitted. Phonon lasers could provide advanced ultrasound imaging or highly accurate measuring devices, among other possibilities.
INFORMATION:
Ramesh is a corresponding author of a Nature Materials paper describing this research titled "Crossover from incoherent to coherent phonon scattering in epitaxial oxide superlattices." For a complete list of the co-authors go here
This research was primarily supported by U.S. Department of Energy's Office of Science.
Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit http://www.lbl.gov.
Crossover sound
Unambiguous evidence for coherent phonons in superlattices
2014-02-06
ELSE PRESS RELEASES FROM THIS DATE:
Grasshoppers are what they eat
2014-02-06
PUBLIC RELEASE DATE: 5-Feb-2014
[
| E-mail
]
var addthis_pub="eurekalert"; var addthis_options = "favorites, delicious, digg, facebook, twitter, google, newsvine, reddit, slashdot, stumbleupon, buzz, more"
Share
Contact: Beth Parada
apps@botany.org
American Journal of Botany
Grasshoppers are what they eat
New method to extract plant DNA from grasshopper guts improves understanding of plant-insect interactions
VIDEO:
This is a demonstration of grasshopper ...
Heavy metal in the early cosmos
2014-02-06
Ab initio: "From the beginning."
It's a term used in science to describe ...
New study finds early universe 'warmed up' later than previously believed
2014-02-06
A new study from Tel Aviv University reveals that black holes, formed from the first stars in our ...
Whales and human-related activities overlap in African waters
2014-02-06
Scientists with the Wildlife Conservation Society, Oregon State University, Stanford ...
Obesity treatment using stem cells is the topic of 2013's most-visited news release on EurekAlert!
2014-02-06
For the second year in a row, obesity research features prominently in the group of 10 most-visited news releases posted on EurekAlert! ...
Fruit fly microRNA research at Rutgers-Camden offers clues to aging process
2014-02-06
CAMDEN — Diseases like Alzheimer's and Huntington's are often associated with aging, but the biological link between the two is less certain. Researchers at Rutgers University–Camden ...
New evidence shows increase in obesity may be slowing, but not by much
2014-02-06
CHAMPAIGN, Ill. — In his 2014 State of the Union address, President Barack Obama referred to an August 2013 Centers for Disease Control and Prevention study that showed a ...
Monkeys that eat omega-3 rich diet show more developed brain networks
2014-02-06
PORTLAND, Ore. — Monkeys that ate a diet rich in omega-3 fatty acids had brains with highly connected ...
MD Anderson guides intelligent redesign of cancer care delivery model
2014-02-06
HOUSTON – How best to implement key recommendations recently identified ...
Durable end to AIDS will require HIV vaccine development
2014-02-06
WHAT:
Broader global access to lifesaving antiretroviral therapies and wider ...
LAST 30 PRESS RELEASES:
Parents of children with health conditions less confident about a positive school year
New guideline standardizes consent for research participants in Canada
Research as reconciliation: Oil sands and health
AI risks overwriting history and the skills of historians have never been more important, leading academic outlines in new paper
The Lancet Diabetes & Endocrinology: Higher doses of semaglutide can safely enhance weight loss and improve health for adults living with obesity, two new clinical trials confirm
Trauma focused therapy shows promise for children struggling with PTSD
School meals could drive economic growth and food system transformation
Home training for cerebellar ataxias
Dry eyes affect over half the general population, yet only a fifth receive diagnosis and treatment
Researchers sound warning about women with type 2 diabetes taking oral HRT
Overweight and obesity don’t always increase the risk of an early death, Danish study finds
Cannabis use associated with a quadrupling of risk of developing type 2 diabetes, finds study of over 4 million adults
Gestational diabetes linked to cognitive decline in mothers and increased risk of developmental delays, ADHD and autism among children
Could we use eye drops instead of reading glasses as we age?
Patients who had cataracts removed or their eyesight corrected with a new type of lens have good vision over all distances without spectacles
AI can spot which patients need treatment to prevent vision loss in young adults
Half of people stop taking popular weight-loss drug within a year, national study finds
Links between diabetes and depression are similar across Europe, study of over-50s in 18 countries finds
Smoking increases the risk of type 2 diabetes, regardless of its characteristics
Scientists trace origins of now extinct plant population from volcanically active Nishinoshima
AI algorithm based on routine mammogram + age can predict women’s major cardiovascular disease risk
New hurdle seen to prostate screening: primary-care docs
MSU researchers explore how virtual sports aid mental health
Working together, cells extend their senses
Cheese fungi help unlock secrets of evolution
Researchers find brain region that fuels compulsive drinking
Mental health effects of exposure to firearm violence persist long after direct exposure
Research identifies immune response that controls Oropouche infection and prevents neurological damage
University of Cincinnati, Kent State University awarded $3M by NSF to share research resources
Ancient DNA reveals deeply complex Mastodon family and repeated migrations driven by climate change
[Press-News.org] Crossover soundUnambiguous evidence for coherent phonons in superlattices