Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Scientists Discover New Way to Study Nanostructures

Atomic-scale mechanical motions in nanowires can be excited by high-frequency alternating superconducting Josephson currents. In niobium dimer nanowires three vibrational modes were experimentally observed and identified through first-principles theoretical calculations. At top is a curve of the measured conductance plotted versus applied voltage showing a sequence of peaks corresponding to vibrational modes of the dimer of niobium atoms suspended between the left and right tip-electrodes, as depicted in the atomic configuration shown in the middle. (Image: Georgia Tech/Alexei Marchenkov and Uzi Landman)
Atomic-scale mechanical motions in nanowires can be excited by high-frequency alternating superconducting Josephson currents. In niobium dimer nanowires three vibrational modes were experimentally observed and identified through first-principles theoretical calculations. At top is a curve of the measured conductance plotted versus applied voltage showing a sequence of peaks corresponding to vibrational modes of the dimer of niobium atoms suspended between the left and right tip-electrodes, as depicted in the atomic configuration shown in the middle. (Image: Georgia Tech/Alexei Marchenkov and Uzi Landman)

Abstract:
Scientists at the Georgia Institute of Technology have discovered a phenomenon which allows measurement of the mechanical motion of nanostructures by using the AC Josephson effect. The findings, which may be used to identify and characterize structural and mechanical properties of nanoparticles, including materials of biological interest, appear online in the journal Nature Nanotechnology.

Scientists Discover New Way to Study Nanostructures

Atlanta, GA | Posted on July 24th, 2007

The AC Josephson effect refers to work that Brian Josephson published in 1962 regarding the flow of an electrical current between superconductors. In this work, for which he shared a 1973 Nobel Prize, Josephson predicted that when a constant voltage difference is maintained across two weakly linked superconductors separated by a thin insulating barrier (an arrangement now known as a Josephson junction), an alternating electrical current would flow through the junction (imagine turning on a water faucet and having the water start flowing up as well as down once it leaves the spigot). The frequency of the current oscillations is directly related to the applied voltage.

These predictions were fully confirmed by an immense number of experiments, and the standard volt is now defined in terms of the frequency of the Josephson AC current. The Josephson effect has numerous applications in physics, computing and sensing technologies. It can be used for ultra high sensitive detection of electromagnetic radiation, extremely weak magnetic fields and in superconducting quantum computing bits.

Now, experimental physicist Alexei Marchenkov and theoretician Uzi Landman at Georgia Tech have discovered that the AC Josephson effect can be used to detect mechanical motion of atoms placed in the Josephson junction.

"We show here that in addition to being able to detect the effects of electromagnetic radiation on the AC Josephson current, one can also use it to probe mechanical motions of atoms or molecules placed in the junction," said Landman, director of the Center for Computational Materials Science, Regents and Institute professor, and Callaway
Chair of Physics at Georgia Tech. "The prospect of being able to explore, and perhaps utilize, atomic-scale phenomena using this effect is very exciting."

In January 2007, Marchenkov and Landman published a paper in Physical Review Letters detailing their discovery that fluctuations in the conductance of ultra-thin niobium nanowires are caused by a pair of atoms, known as a dimer, shuttling back and forth between the bulk electrical leads.

In this latest research, Marchenkov and Landman, along with their collaborators Zhenting Dai, Brandon Donehoo and Robert Barnett, report that when a microfabricated junction assembly is held below its superconducting transition temperature, unusual features are found in traces of the electrical conductance measured as a function of the applied voltage.

"In our experiments, only nanowires - which we know now to contain a single dimer have consistently shown a series of additional peaks in the conductance versus voltage curves. Since a peak in such measurements signifies a resonance and knowing that we have intrinsic high-frequency Josephson current oscillations, we started looking into the possible physical mechanisms," said Marchenkov, assistant professor in the School of Physics.

The team hypothesized that the new measured peaks likely originate from mechanical motions of the dimer, which causes enhancement of the electrical current at particular values of the applied voltage. At each of the peak voltages, the frequency of the AC Josephson current would resonate with the vibrational frequency of the nanostructure in the junction.

Subsequent first principles calculations by Landman's team predicted that such peaks would occur at three different frequencies, or voltages, and their integer multiples. One corresponds to a back and forth vibration of the dimer suspended between the two niobium electrode tips, a second corresponds to motion in the direction perpendicular to the axis connecting the two tips, and the remaining corresponds to a wagging, or rocking, vibration of the dimer about the inter-tip axis. Ensuing targeted experiments demonstrated that the resonance peaks disappear gradually as one approaches the superconducting transition temperature from below, while their positions do not change. These observations, exhaustive qualitative and quantitative agreement between experimental measurements and theoretical predictions confirm that vibrational motions of the nanowire atoms are indeed the cause for the newly observed conductance peaks.

Marchenkov and Landman plan to further explore vibrational effects in weak link junctions, using the information obtained through these studies for determining vibrational characteristics, atomic arrangements, and transport mechanisms in metallic,
organic and biomolecular nanostructures.

"One of our aims is the development of devices and sensing methodologies that utilize the insights gained from our research," said Landman.

####

About Georgia Institute of Technology
The Georgia Institute of Technology is one of the nation's premiere research universities. Ranked eighth among U.S. News & World Report's top public universities, Georgia Tech's 17,000 students are enrolled in its Colleges of Architecture, Computing, Engineering, Liberal Arts, Management and Sciences. Tech is among the nation's top producers of women and African-American engineers. The Institute offers research opportunities to both undergraduate and graduate students and is home to more than 100 interdisciplinary units plus the Georgia Tech Research Institute.

For more information, please click here

Contacts:
David Terraso
Institute Communications & Public Affairs

404-385-2966

Copyright © Georgia Institute of Technology

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

Uzi Landman

Alexei Marchenkov

Related News Press

Chip Technology

French Institutes IRT Nanoelec and CMP Team up to Offer World’s First Service for Post-process 3D Technologies on Multi-Project-Wafer March 5th, 2015

Experiment and theory unite at last in debate over microbial nanowires: New model and experiments settle debate over metallic-like conductivity of microbial nanowires in bacterium March 4th, 2015

Magnetic vortices in nanodisks reveal information: Researchers from Dresden and Jülich use microwaves to read out information from smallest storage devices March 4th, 2015

The taming of magnetic vortices: Unified theory for skyrmion-materials March 3rd, 2015

Sensors

Experiment and theory unite at last in debate over microbial nanowires: New model and experiments settle debate over metallic-like conductivity of microbial nanowires in bacterium March 4th, 2015

Pens filled with high-tech inks for do-it-yourself sensors March 3rd, 2015

Penn researchers develop new technique for making molybdenum disulfide: Extra control over monolayer material with advantages over graphene February 19th, 2015

Researchers build atomically thin gas and chemical sensors: Sensors made of molybdenum disulfide are small, thin and have a high level of selectivity when detecting gases and chemicals February 19th, 2015

Discoveries

Enhanced Graphene Components for Next Generation Racing Yacht March 5th, 2015

American Chemical Society Presidential Symposia: nanoscience, international chemistry March 5th, 2015

Magnetic vortices in nanodisks reveal information: Researchers from Dresden and Jülich use microwaves to read out information from smallest storage devices March 4th, 2015

CiQUS researchers obtain high-quality perovskites over large areas by a chemical method March 4th, 2015

Announcements

The George Washington University Opens Science and Engineering Hall, Largest Building of Its Kind in D.C.: Building Represents Significant Investment in Research Programs and Facilities; Commitment to Solve Global Problems, Improve Lives of Millions March 5th, 2015

Anousheh Ansari Wins the National Space Society's Space Pioneer Award for "Service to the Space Community" March 5th, 2015

Enhanced Graphene Components for Next Generation Racing Yacht March 5th, 2015

Get ready for NanoDays! March 5th, 2015

Tools

Keysight Technologies Shifts to Direct Sales of High-Performance Products in North America March 3rd, 2015

Forbidden quantum leaps possible with high-res spectroscopy March 2nd, 2015

International research partnership tricks the light fantastic March 2nd, 2015

Important step towards quantum computing: Metals at atomic scale March 2nd, 2015

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2015 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE