Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Asymmetric feature shows puzzling face for superconductivity

03.08.2004


The weird behavior of electrons tunneling across an atomically flat interface within a cuprate superconductor has defied explanation by theories of high-temperature superconductivity.



As will be reported in the journal Physical Review Letters, a team of scientists led by physics professor James Eckstein at the University of Illinois at Urbana-Champaign has found a large particle-hole asymmetry in the density of states of excitations in high-temperature superconducting tunnel junctions embedded in a single crystal heterostructure. Since superconductors are supposed to possess particle-hole symmetry — according to current theories — new theoretical work may be required to explain the strange results.

In tunneling spectroscopy of superconductors, the differential conductance is proportional to the density of states in the superconductor. "Below the superconducting transition, the tunneling conductance showed a large unexpected asymmetrical feature near zero bias," Eckstein said. "This is evidence that crystals of high-temperature superconductors, atomically truncated with a titanate layer, have intrinsically broken particle-hole symmetry."


At negative bias (corresponding to tunneling of electrons from states with particle-like character) the spectra exhibited the expected superconducting gap. However, at positive bias (corresponding to tunneling of electrons into states with hole-like character) the spectra showed a dramatic step-like increase. "This clearly demonstrates the breaking of symmetry between particle-like and hole-like excitations at this interface in the superconducting state," Eckstein said.

The junction heterostructures were very carefully grown by oxide molecular beam epitaxy and optimized using in situ monitoring techniques, resulting in unprecedented crystalline perfection of the superconductor/insulator interface. It was the precise truncation of the crystal lattice at the calcium titanate interface that led to the new results.

"The interface density of states was strongly modified by superconductivity, as expected, but the resulting excitation spectrum was not particle-hole symmetric," Eckstein said. "This indicates that at the surface into which the tunneling occurred, superconductivity is very different from what it is like away from the interface."

While the origin of this effect is still being debated, it depends critically on the high degree of crystalline perfection obtained at the insulator-superconductor interface.

"The presence of this well-defined interface obviously perturbs the superconductivity," Eckstein said. "So these results can provide a new test for theories of high-temperature superconductivity."

James E. Kloeppel | EurekAlert!
Further information:
http://www.uiuc.edu

More articles from Physics and Astronomy:

nachricht Thermal Radiation from Tiny Particles
22.06.2018 | Universität Greifswald

nachricht Temperature-controlled fiber-optic light source with liquid core
20.06.2018 | Leibniz-Institut für Photonische Technologien e. V.

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: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Polar ice may be softer than we thought

22.06.2018 | Earth Sciences

Better model of water under extreme conditions could aid understanding of Earth's mantle

21.06.2018 | Earth Sciences

What are the effects of coral reef marine protected areas?

21.06.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>