Experimental probing of the anisotropy of the empty p states near the Fermi level in MgB2

We have studied the boron K edge in the superconductor MgB2 by electron energy loss spectroscopy (EELS) and experimentally resolved the empty p states at the Fermi level that have previously been observed within an energy window of 0.8 eV by soft x-ray absorption spectroscopy. Using angular-resolved EELS, we find that these states at the immediate edge onset have pxy character in agreement with predictions from first-principle electronic structure calculations.