Angle-resolved soft x-ray spectroscopy study of the electronic states of single-crystal MgB2 -: art. no. 174519

Angle-resolved soft x-ray measurements made at the boron K edge in single-crystal MgB2 provide insights into the B 2p local partial density of both unoccupied and occupied band states. The strong variation of absorption with incident angle of exciting x rays permits the clear separation of contributions from sigma states in the boron plane and pi states normal to the plane. A careful comparison with theory accurately determines the energy of selected critical k points in the conduction band. Resonant inelastic x-ray emission at an incident angle of 15degrees shows a large enhancement of the emission spectra within about 0.5 eV of the Fermi level that is absent at 45degrees and is much reduced at 60degrees. We conclude that momentum transferred from the resonant inelastic x-ray scattering process couples empty and filled states across the Fermi level.