Electron-Hole Symmetry and Magnetic Coupling in Antiferromagnetic LaOFeAs

TL;DR

This paper investigates the electronic, magnetic, and superconducting properties of LaOFeAs, revealing how doping influences its antiferromagnetic phase, pseudogap formation, and magnetic coupling, contributing to understanding high-temperature superconductivity.

Contribution

It provides detailed analysis of the magnetic coupling, pseudogap behavior, and doping effects in LaOFeAs, highlighting the dependence of exchange interactions on magnetic symmetry and structural parameters.

Findings

High Tc superconductivity at doping x~0.1 with T_c up to 55 K.

Presence of a pseudogap in Fe 3d states at the Fermi level.

Strong dependence of exchange coupling on AFM symmetry and Fe-As distance.

Abstract

When either electron or hole doped at concentrations $x\sim 0.1$, the LaOFeAs family displays remarkably high temperature superconductivity with T$_c$ up to 55 K. In the most energetically stable $\vec Q_M = (\pi,\pi)$ antiferromagnetic (AFM) phase comprised of tetragonal-symmetry breaking alternating chains of aligned spins, there is a deep pseudogap in the Fe 3d states centered at the Fermi energy, and very strong magnetophonon coupling is uncovered. Doping (of either sign) beyond $x \sim 0.1$ results in Fe 3d heavy mass carriers ($m^*\sim 4-8$) with a large Fermi surface. Calculated Fe-Fe transverse exchange couplings $J_{ij}(R)$ reveal that exchange coupling is strongly dependent on the AFM symmetry and Fe-As distance.