Fermi-liquid based theory for the in-plane magnetic anisotropy in untwinned high-T$_c$ superconductors

TL;DR

This paper develops a Fermi-liquid based theoretical model to explain the in-plane magnetic anisotropy observed in untwinned high-Tc superconductors, aligning well with experimental data and challenging stripe-based interpretations.

Contribution

The study extends previous Fermi-liquid models by including orthorhombicity, providing a conventional explanation for magnetic anisotropy in high-Tc superconductors.

Findings

Strong anisotropy in two-dimensional spin excitations

Good agreement with experimental data on YBa2Cu3O6.85

Contrasts with stripe-based interpretations

Abstract

Using a generalized RPA-type theory we calculate the in-plane anisotropy of the magnetic excitations in hole-doped high-$T_c$ superconductors. Extending our earlier Fermi-liquid based studies on the resonance peak by inclusion of orthorhombicity we still find two-dimensional spin excitations, however, being strongly anisotropic. This reflects the underlying anisotropy of the hopping matrix elements and of the resultant superconducting gap function. We compare our calculations with new experimental data on {\it fully untwinned} ${YBa}_2{Cu}_3{O}_{6.85}$ and find good agreement. Our results are in contrast to earlier interpretations on the in-plane anisotropy in terms of stripes (H. Mook {\it et al.}, Nature {\bf 404}, 729 (2000)), but reveal a conventional solution to this important problem.