Measuring the Hole State Anisotropy in MgB2 by Electron Energy-Loss Spectroscopy

TL;DR

This study uses electron energy-loss spectroscopy and density functional theory to analyze the anisotropic hole states in MgB2, revealing orientation-dependent spectral features and demonstrating EELS as a tool for probing superconducting properties at the nanoscale.

Contribution

It provides the first detailed analysis of hole state anisotropy in MgB2 using EELS and density functional calculations, highlighting the potential of EELS for superconductivity research.

Findings

Significant orientation-dependent changes in B K-edge fine structure.

Pre-peak of B K-edge contains information on pxy and pz hole states.

EELS can probe local charge carrier concentration and superconducting properties.

Abstract

We have examined polycrystalline MgB2 by electron energy loss spectroscopy (EELS) and density of state calculations. In particular, we have studied two different crystal orientations, [110] and [001] with respect to the incident electron beam direction, and found significant changes in the near-edge fine-structure of the B K-edge. Density functional theory suggests that the pre-peak of the B K-edge core loss is composed of a mixture of pxy and pz hole states and we will show that these contributions can be distinguished only with an experimental energy resolution better than 0.5 eV. For conventional TEM/STEM instruments with an energy resolution of ~1.0 eV the pre-peak still contains valuable information about the local charge carrier concentration that can be probed by core-loss EELS. By considering the scattering momentum transfer for different crystal orientations, it is possible to analytically separate pxy and pz components from of the experimental spectra With careful experiments and analysis, EELS can be a unique tool measuring the superconducting properties of MgB2, doped with various elements for improved transport properties on a sub-nanometer scale.