Electronic Structure of B-2$p\sigma$ and $p\pi$ States in MgB$_2$, AlB$_2$ and ZrB$_2$ Single Crystals

TL;DR

This study investigates the electronic structure of MgB$_2$, AlB$_2$, and ZrB$_2$ single crystals, focusing on B-2$p$ states, and finds electron correlation effects are minimal, supporting the importance of electron-phonon interactions in superconductivity.

Contribution

It provides experimental evidence that electron correlation effects are negligible in these compounds, emphasizing the role of electron-phonon interactions in their superconducting behavior.

Findings

Electron correlation effects are less than 0.2 eV, within experimental error.

Discrepancies between observed and calculated PDOS are not due to electron correlation.

Electron-phonon interaction is crucial for superconductivity in these materials.

Abstract

The effect of electron correlation (EC) on the electronic structure in MgB$_2$, AlB$_2$ and ZrB$_2$, is studied by examining the partial density of states (PDOS) of B-2$p\sigma$ and $p\pi$ orbitals using the polarization dependence of x-ray emission and absorption spectra. The discrepancies between observed and calculated PDOSs cannot be attributed to EC effects. The present results suggest that the EC effect is less than the experimental error ($\sim$ 0.2 eV), which indirectly supports a scenario that electron-phonon interaction plays an essential role in the occurrence of superconductivity.