Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Copper-oxide plane at surface of superconductor has surprising properties

27.08.2002


The peculiar behavior of high-temperature superconductors has baffled scientists for many years. Now, by imaging the copper-oxide plane in a cuprate superconductor for the first time, researchers at the University of Illinois at Urbana-Champaign have found several new pieces to this important puzzle.

As reported in the Aug. 19 issue of Physical Review Letters, physics professor Ali Yazdani, graduate student Shashank Misra, and colleagues used a scanning tunneling microscope to demonstrate that a single copper-oxide plane can form a stable layer at the superconductor’s surface. This plane behaves differently when exposed at the surface than when buried inside the crystal, the researchers discovered, offering additional insight into the behavior of high-temperature superconductors.

"In contrast to previous studies, we found that this copper-oxide layer exhibits an unusual suppression of tunneling conductance at low energies," Yazdani said. "We think the orbital symmetry of the plane’s electronic states may be influencing the tunneling process and is responsible for the strange behavior we observed at the surface."



Surface-sensitive techniques, such as electron tunneling and photoemission, have been crucial in gleaning information about high-temperature superconductors, Yazdani said. But it hasn’t always been clear from which layer the information was coming. By imaging at the atomic scale and probing on the nanoscale, the researchers achieved much higher precision.

"High-temperature superconductors are layered compounds containing one or more copper-oxide planes and other layers that act as charge reservoirs," Yazdani said. "Like dopants in a semiconductor, these layers donate charge carriers to the copper-oxide planes, making them conducting. The strong electronic interactions in the copper-oxide planes are responsible for the material’s unusual electronic properties."

To image the surface of thin films of superconducting crystal, Yazdani and his colleagues used a low-temperature scanning tunneling microscope that they built at Illinois. By exploring large areas of the sample and correlating the STM topographic images with X-ray crystallographic data, the researchers were able to identify individual layers of copper oxide and of bismuth oxide, and then measure their electronic properties.

"With the STM, we can send electrons through the tip and measure the rate at which they flow into the surface," Yazdani said. "We found a very strong contrast in the spectra taken on the two surfaces. The electron tunneling in the copper-oxide plane was strongly suppressed at low energies."

This behavior is unexpected in a d-wave superconductor, Yazdani said, and could demonstrate the dramatic influence of the layered structure on the surface electronic properties. The observations can best be explained by the way in which the STM tip couples to the electronic states of the copper-oxide plane, the researchers concluded.

"At low energies, electrons from the tip are constrained by the orbital symmetry of the plane’s electronic wave function, which resembles a cloverleaf pattern," Yazdani said. "This directional dependence of the current can explain the suppressed tunneling."

Previous measurements had been performed on surfaces terminated with other layers – bismuth oxide, for example – where the copper-oxide plane was buried under the surface. In those experiments, however, it was not apparent how the STM tip was coupling to the copper-oxide plane, Yazdani said.

"You could theorize that the other layers had no effect on the measurement, but that flies in the face of our experiment," Yazdani said. "From our results, it is clear that what you put at the surface makes a huge difference in what you measure."

Having direct access to the surface means scientists can begin manipulating its properties by changing what’s under the surface. The Illinois work also opens a new methodology for probing electrons in the copper-oxide plane.

Collaborators on the project were physics professor James Eckstein, postdoctoral research associate Tiziana DiLuccio, and graduate students Seongshik Oh and Daniel Hornbaker. The National Science Foundation, Office of Naval Research and the U.S. Department of Energy funded the work.

Jim Kloeppel | UIUC News Bureau
Further information:
http://www.news.uiuc.edu/

More articles from Physics and Astronomy:

nachricht Convenient location of a near-threshold proton-emitting resonance in 11B
29.05.2020 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences

nachricht A special elemental magic
28.05.2020 | Kyoto University

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: Biotechnology: Triggered by light, a novel way to switch on an enzyme

In living cells, enzymes drive biochemical metabolic processes enabling reactions to take place efficiently. It is this very ability which allows them to be used as catalysts in biotechnology, for example to create chemical products such as pharmaceutics. Researchers now identified an enzyme that, when illuminated with blue light, becomes catalytically active and initiates a reaction that was previously unknown in enzymatics. The study was published in "Nature Communications".

Enzymes: they are the central drivers for biochemical metabolic processes in every living cell, enabling reactions to take place efficiently. It is this very...

Im Focus: New double-contrast technique picks up small tumors on MRI

Early detection of tumors is extremely important in treating cancer. A new technique developed by researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from normal tissue. The work is published May 25 in the journal Nature Nanotechnology.

researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from...

Im Focus: I-call - When microimplants communicate with each other / Innovation driver digitization - "Smart Health“

Microelectronics as a key technology enables numerous innovations in the field of intelligent medical technology. The Fraunhofer Institute for Biomedical Engineering IBMT coordinates the BMBF cooperative project "I-call" realizing the first electronic system for ultrasound-based, safe and interference-resistant data transmission between implants in the human body.

When microelectronic systems are used for medical applications, they have to meet high requirements in terms of biocompatibility, reliability, energy...

Im Focus: When predictions of theoretical chemists become reality

Thomas Heine, Professor of Theoretical Chemistry at TU Dresden, together with his team, first predicted a topological 2D polymer in 2019. Only one year later, an international team led by Italian researchers was able to synthesize these materials and experimentally prove their topological properties. For the renowned journal Nature Materials, this was the occasion to invite Thomas Heine to a News and Views article, which was published this week. Under the title "Making 2D Topological Polymers a reality" Prof. Heine describes how his theory became a reality.

Ultrathin materials are extremely interesting as building blocks for next generation nano electronic devices, as it is much easier to make circuits and other...

Im Focus: Rolling into the deep

Scientists took a leukocyte as the blueprint and developed a microrobot that has the size, shape and moving capabilities of a white blood cell. Simulating a blood vessel in a laboratory setting, they succeeded in magnetically navigating the ball-shaped microroller through this dynamic and dense environment. The drug-delivery vehicle withstood the simulated blood flow, pushing the developments in targeted drug delivery a step further: inside the body, there is no better access route to all tissues and organs than the circulatory system. A robot that could actually travel through this finely woven web would revolutionize the minimally-invasive treatment of illnesses.

A team of scientists from the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart invented a tiny microrobot that resembles a white blood cell...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

Aachen Machine Tool Colloquium AWK'21 will take place on June 10 and 11, 2021

07.04.2020 | Event News

International Coral Reef Symposium in Bremen Postponed by a Year

06.04.2020 | Event News

 
Latest News

Black nitrogen: Bayreuth researchers discover new high-pressure material and solve a puzzle of the periodic table

29.05.2020 | Materials Sciences

Argonne researchers create active material out of microscopic spinning particles

29.05.2020 | Materials Sciences

Smart windows that self-illuminate on rainy days

29.05.2020 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>