Potier, Beth

English

University of New Hampshire

University of New Hampshire
University of New Hampshire Scholars' Repository
Media Relations Administrative Offices
7-5-2007
UNH Researchers Prove Existence Of New Type
Of Electron Wave
Beth Potier
UNH Media Relations
Follow this and additional works at: https://scholars.unh.edu/news
This News Article is brought to you for free and open access by the Administrative Offices at University of New Hampshire Scholars' Repository. It has
been accepted for inclusion in Media Relations by an authorized administrator of University of New Hampshire Scholars' Repository. For more
information, please contact nicole.hentz@unh.edu.
Recommended Citation
Potier, Beth, "UNH Researchers Prove Existence Of New Type Of Electron Wave" (2007). UNH Today. 934.
https://scholars.unh.edu/news/934
9/11/17, 12(20 PMUNH Researchers Prove Existence Of New Type Of Electron Wave
Page 1 of 2http://www.unh.edu/delete/news/cj_nr/2007/july/bp05electron.cfm.html
 
UNH Researchers Prove Existence Of New Type Of
Electron Wave
Contact:  Beth Potier 
603-862-1566
UNH Media Relations
July 5, 2007
Editors and reporters: Bogdan Diaconescu is available at bogdan@einstein.unh.edu
or by cell: 603-978-2664. Karsten Pohl is available at karsten.pohl@unh.edu or by
cell in Germany: 011-49-170-653-3654.
DURHAM, N.H. – New research led by University of New Hampshire physicists has proved the
existence of a new type of electron wave on metal surfaces: the acoustic surface plasmon,
which will have implications for developments in nano-optics, high-temperature
superconductors, and the fundamental understanding of chemical reactions on surfaces. The
research, led by Bogdan Diaconescu and Karsten Pohl of UNH, is published in the July 5 issue
of the journal “Nature.”
“The existence of this wave means that the electrons on the surfaces of copper, iron, beryllium
and other metals behave like water on a lake’s surface,” says Pohl, associate professor of
physics at UNH. “When a stone is thrown into a lake, waves spread radially in all directions. A
similar wave can be created by the electrons on a metal surface when they are disturbed, for
instance, by light.”
Acoustic surface plasmons have long been predicted on merely theoretical grounds, their
existence has been extraordinarily difficult to prove experimentally. “Just one year ago,
another group of scientists concluded that these waves do not exist,” says Diaconescu, a
postdoctoral research associate in the Condensed Matter Group of the physics department at
UNH. “These researchers have probably not been able to find the acoustic plasmon because
the experiments require extreme precision and great patience. One attempt after the other
did not show anything if, for example, the surface was not prepared well enough or the
detectors were not adjusted precisely enough.”
The new experiment that found the acoustic surface plasmon used an extremely precise
electron gun, which shoots slow electrons on a specially prepared surface of a beryllium
crystal. When the electrons are reflected back from the electron lake on the surface of the
metal, some of them lose an amount of energy that corresponds to the excitation of an
acoustic plasmon wave. This energy loss could be measured with a detector that was placed in
an ultra-high vacuum chamber, together with the beryllium sample. The energy loss is small
but corresponds exactly to the theoretical prediction.
Research on metal surfaces is important for the development of new industrial catalysts and
for the cleaning the exhaust of factories and cars. As the new plasmons are very likely to play
a role in chemical reactions on metal surfaces, theoretical and experimental research will have
9/11/17, 12(20 PMUNH Researchers Prove Existence Of New Type Of Electron Wave
Page 2 of 2http://www.unh.edu/delete/news/cj_nr/2007/july/bp05electron.cfm.html
to take them into account as a new phenomenon in the future. In addition, there are several
promising perspectives in nano-microscopy and optical signal processing when the new
plasmons are excited directly with light diffracted off very small nano-features. The
researchers estimate that, depending on their energy, the waves spread down to a few
nanometers (one millionth of a millimeter), and die out after a few femtoseconds (one
millionth of a billionth of a second) after they have been created, thus witnessing very fast
chemical processes at the atomic scale.
Another potential application is using the waves to carry optical signals along nanometer-wide
channels for up to few micrometers and as such allowing the integration of optical signal
propagation and processing devices on nanometer-length scales. And one of the most
interesting but still very speculative applications of the plasmons relates to high temperature
superconductivity. It is known today that the superconductivity happens in two-dimensional
sheets in the material, which give rise to the special electron pairs which can move without
resistance through the conductor. How this happens precisely is unclear but acoustic plasmons
could be part of the explanation. If this is the case, it is a great advantage that it is now
possible to study the new acoustic plasmons on surfaces, where they is much easier to probe
them than inside the material.
Diaconescu and Pohl received funding for this research from the National Science Foundation.
To download the paper, “Low-energy acoustic plasmons at metal surfaces,” click
here:  http://unh.edu/news/docs/plasmons.pdf
An image is available to download here:
http://davinci.unh.edu/~bogdan/docu/ASP_Be(0001)/ASP-and-SP_Be0001.tif
Description: When a small charge is placed close to a metal surface, standing electron waves
are created. These are shown in the lower part of the figure. Another type of waves, called
plasmons, are created when the charge is slightly jiggled. These plasmons, which need a
rather high energy to be excited, have been known for a long time and are present on the
surfaces of all metals.  Bogdan Diaconescu and Karsten Pohl with their colleagues have now
proved the existence of a new type of plasmon, called “acoustic,” which can be excited with
any energy (wavelength) and which can therefore be compared to water waves in a lake. The
new type of wave is superimposed on the standing waves and is shown in the upper part of
the figure.


UNH Researchers Prove Existence Of New Type Of Electron Wave

UNH Scholars' Repository

University of New HampshireUniversity of New Hampshire Scholars' RepositoryMedia Relations Administrative Offices7-5-2007UNH Researchers Prove Existence Of New TypeOf Electron WaveBeth PotierUNH Media RelationsFollow this and additional works at: https://scholars.unh.edu/newsThis News Article is brought to you for free and open access by the Administrative Offices at University of New Hampshire Scholars' Repository. It hasbeen accepted for inclusion in Media Relations by an authorized administrator of University of New Hampshire Scholars' Repository. For moreinformation, please contact nicole.hentz@unh.edu.Recommended CitationPotier, Beth, "UNH Researchers Prove Existence Of New Type Of Electron Wave" (2007). UNH Today. 934.https://scholars.unh.edu/news/9349/11/17, 12(20 PMUNH Researchers Prove Existence Of New Type Of Electron WavePage 1 of 2http://www.unh.edu/delete/news/cj_nr/2007/july/bp05electron.cfm.html UNH Researchers Prove Existence Of New Type OfElectron WaveContact:  Beth Potier 603-862-1566UNH Media RelationsJuly 5, 2007Editors and reporters: Bogdan Diaconescu is available at bogdan@einstein.unh.eduor by cell: 603-978-2664. Karsten Pohl is available at karsten.pohl@unh.edu or bycell in Germany: 011-49-170-653-3654.DURHAM, N.H. – New research led by University of New Hampshire physicists has proved theexistence of a new type of electron wave on metal surfaces: the acoustic surface plasmon,which will have implications for developments in nano-optics, high-temperaturesuperconductors, and the fundamental understanding of chemical reactions on surfaces. Theresearch, led by Bogdan Diaconescu and Karsten Pohl of UNH, is published in the July 5 issueof the journal “Nature.”“The existence of this wave means that the electrons on the surfaces of copper, iron, berylliumand other metals behave like water on a lake’s surface,” says Pohl, associate professor ofphysics at UNH. “When a stone is thrown into a lake, waves spread radially in all directions. Asimilar wave can be created by the electrons on a metal surface when they are disturbed, forinstance, by light.”Acoustic surface plasmons have long been predicted on merely theoretical grounds, theirexistence has been extraordinarily difficult to prove experimentally. “Just one year ago,another group of scientists concluded that these waves do not exist,” says Diaconescu, apostdoctoral research associate in the Condensed Matter Group of the physics department atUNH. “These researchers have probably not been able to find the acoustic plasmon becausethe experiments require extreme precision and great patience. One attempt after the otherdid not show anything if, for example, the surface was not prepared well enough or thedetectors were not adjusted precisely enough.”The new experiment that found the acoustic surface plasmon used an extremely preciseelectron gun, which shoots slow electrons on a specially prepared surface of a berylliumcrystal. When the electrons are reflected back from the electron lake on the surface of themetal, some of them lose an amount of energy that corresponds to the excitation of anacoustic plasmon wave. This energy loss could be measured with a detector that was placed inan ultra-high vacuum chamber, together with the beryllium sample. The energy loss is smallbut corresponds exactly to the theoretical prediction.Research on metal surfaces is important for the development of new industrial catalysts andfor the cleaning the exhaust of factories and cars. As the new plasmons are very likely to playa role in chemical reactions on metal surfaces, theoretical and experimental research will have9/11/17, 12(20 PMUNH Researchers Prove Existence Of New Type Of Electron WavePage 2 of 2http://www.unh.edu/delete/news/cj_nr/2007/july/bp05electron.cfm.htmlto take them into account as a new phenomenon in the future. In addition, there are severalpromising perspectives in nano-microscopy and optical signal processing when the newplasmons are excited directly with light diffracted off very small nano-features. Theresearchers estimate that, depending on their energy, the waves spread down to a fewnanometers (one millionth of a millimeter), and die out after a few femtoseconds (onemillionth of a billionth of a second) after they have been created, thus witnessing very fastchemical processes at the atomic scale.Another potential application is using the waves to carry optical signals along nanometer-widechannels for up to few micrometers and as such allowing the integration of optical signalpropagation and processing devices on nanometer-length scales. And one of the mostinteresting but still very speculative applications of the plasmons relates to high temperaturesuperconductivity. It is known today that the superconductivity happens in two-dimensionalsheets in the material, which give rise to the special electron pairs which can move withoutresistance through the conductor. How this happens precisely is unclear but acoustic plasmonscould be part of the explanation. If this is the case, it is a great advantage that it is nowpossible to study the new acoustic plasmons on surfaces, where they is much easier to probethem than inside the material.Diaconescu and Pohl received funding for this research from the National Science Foundation.To download the paper, “Low-energy acoustic plasmons at metal surfaces,” clickhere:  http://unh.edu/news/docs/plasmons.pdfAn image is available to download here:http://davinci.unh.edu/~bogdan/docu/ASP_Be(0001)/ASP-and-SP_Be0001.tifDescription: When a small charge is placed close to a metal surface, standing electron wavesare created. These are shown in the lower part of the figure. Another type of waves, calledplasmons, are created when the charge is slightly jiggled. These plasmons, which need arather high energy to be excited, have been known for a long time and are present on thesurfaces of all metals.  Bogdan Diaconescu and Karsten Pohl with their colleagues have nowproved the existence of a new type of plasmon, called “acoustic,” which can be excited withany energy (wavelength) and which can therefore be compared to water waves in a lake. Thenew type of wave is superimposed on the standing waves and is shown in the upper part ofthe figure.

https://scholars.unh.edu/cgi/viewcontent.cgi?article=1933&amp;context=news

UNH Researchers Prove Existence Of New Type Of Electron Wave

Abstract

Similar works

Full text

Available Versions

University of New Hampshire

UNH Scholars' Repository