Using new imaging methods, scientists at Brookhaven National Laboratory have confirmed that electron pairs that carry electrical current emerge above the transition temperature before superconductivity sets in. But the pairing only occurs along the directions in which copper atoms are bonded with oxygen atoms.
The imaging method used is known as angle-resolved photoemission spectroscopy (ARPES). Scientists at Brookhaven used beams of light from the National Synchrotron Light Source to create a sample whereby the energy spectrum of the electrons emitted could be analyzed. Increasing the resolution of these images allowed scientists to get a clear view of the energy spectrum.
“By improving our resolution we can use ARPES to see the few electrons that occasionally occupy levels above the Fermi level,” said Brookhaven scientist Peter Johnson. “We have devised ways to sharpen our images so we can look at the weak signals from above the Fermi level in finer and finer detail.”
