|Photo By Michal Jarmoluk via Pixnio|
All superconductors have been metals because of their composition, having the largest number of loosely bound electrons that cannot resist electricity. For the past 50 years, scientists have been relying on these metals for superconductivity until they found a new material to do the job -- strontium titanate.
First Oxide Material That Has Superconductivity
Strontium titanate is an oxide of the alkaline earth metal strontium and the transition metal titanium. Even though its normal characteristics do not indicate superconductivity, closer inspection revealed that when conditions are right, the few free-roaming electrons can provide that unique metallic property.
Scientists at the Department of Energy and Stanford University discovered the unique metallic property in strontium titanate. In theory, the natural vibrations through the atomic framework of a material induce superconductivity. The vibrations cause the electrons to pair up and condense that allows the flow of electrical current. Unconventionally, scientists do not know the mechanism behind the pairing of electrons in unusual superconductors.
In the study, the investigators used tunneling spectroscopy to find out how the electrons in strontium titanate conduct electricity. With the instrument, they found that the material does the exact opposite of what other superconductors do. The atomic framework displayed strong vibrations, but electrons were few and slow moving. However, certain factors of electrons relevant to superconductivity, such as behavior and density, matched the theory in superconductivity. In the BCS theory, any material with superconductivity loses all resistance to electrical current when the temperature is near absolute zero.
“Thus, strontium titanate seems to be an unconventional superconductor that acts like a conventional one in some respects. This is quite a conundrum and quite a surprise to us. We discovered something that was more confusing than we originally thought, which from a fundamental physics point of view is more profound,” said Harold Hwang, a professor at SLAC National Accelerator Laboratory at DOE.
The discovery of the unconventional superconductivity in the material allowed the scientists to explore the high-temperature superconductivity angle. If harnessed, the new phenomenon can lead to more efficient power lines, levitating trains, and other high-tech technologies.