X-ray absorption spectroscopy and electron energy loss spectroscopy were use to study the fine structure at the K-edge of B in MgB2. In XAS, a peak with a width of 0.7eV was observed at the edge threshold; indicating a narrow energy region with empty B p-states near to the Fermi level. The changes in the near edge structure observed in EELS with direction of the momentum transfer imply that these states have pxpy symmetry. The observations were consistent with electronic structure calculations indicating a narrow energy window of empty pxpy states that fell to zero at 0.8eV above the Fermi level. The disappearance of the pxpy feature in EELS at grain boundaries suggested that this signature might become very useful for probing superconductivity at the nanoscale.

Unraveling the Symmetry of the Hole States Near the Fermi Level in the MgB2 Superconductor. Y.Zhu, A.R.Moodenbaugh, G.Schneider, J.W.Davenport, T.Vogt, Q.Li, G.Gu, D.A.Fischer, J.Tafto: Physical Review Letters, 2002, 88[24], 247002 (3pp)