Momentum densities, Fermi surfaces, and their temperature dependences in Sr2 RuO4 studied by Compton scattering

We have measured Compton profiles of Sr2 RuO4 at 20 K and room temperature to investigate electron momentum densities, Fermi surfaces, and their temperature dependences. Two-dimensional momentum densities have been reconstructed from nine Compton profiles. The Fermi surface signals are observed in the first derivative of the occupation densities in k space, obtained by folding the momentum densities into the first Brillouin zone. The data at T=20 K exhibit Fermi surface signals that reasonably agree with those obtained from band theory. On the other hand, the data at room temperature show the signals strongly suppressed due to temperature. This thermal behavior is not understood using band theory based on the local density approximation, implying the importance of electron correlation in the temperature effect.