Self-energy spectrum
The relation between the energy and momentum of
electrons in the material is shown at different
temperatures. The transition temperature at
which the material becomes superconducting
is about 90 Kelvin; data are shown for temperatures at 40 K (blue dots) and 140 K
(red circles). The green dashed line is the theoretical estimate.
At 40 K, an S-shaped curve appears; the maximum displacement of the data curve from the theory corresponds to a peak in the electron self-energy. This effect is analogous to that now observed by Timusk and co-workers in optical studies. These authors argue that the peak is caused by the interaction of electrons with a magnetic resonance (image and text: Nature 427 692).