Enhanced Orbital Degeneracy in Momentum Space for LaOFeAs

TL;DR

This paper uses first-principles calculations to reveal enhanced orbital degeneracy in LaOFeAs's Fermi surfaces, highlighting the roles of F-doping and pressure in promoting degeneracy, which may be key to understanding its superconductivity.

Contribution

It demonstrates that F-doping and pressure enhance orbital degeneracy in LaOFeAs, providing new insights into the material's electronic structure and superconductivity mechanisms.

Findings

Additional degeneracy exists for electron-type Fermi surfaces.

F-doping and pressure significantly enhance this degeneracy.

Inter-orbital fluctuations may be crucial for superconductivity.

Abstract

The Fermi surfaces (FS) of LaOFeAs (in $k_z$=0 plane) consist of two hole-type circles around $\Gamma$ point, which do not touch each other, and two electron-type co-centered ellipses around M point, which are degenerate along the M-X line. By first-principles calculations, here we show that additional degeneracy exists for the two electron-type FS, and the crucial role of F-doping and pressure is to enhance this orbital degeneracy. It is suggested that the inter-orbital fluctuation is the key point to understand the unconventional superconductivity in these materials.