Tight-binding Hamiltonians for Sr filled ruthenates: application to the gap anisotropy and Hall coefficient in Sr2RuO4

TL;DR

This paper develops accurate tight-binding Hamiltonians for SrRuO3 and Sr2RuO4, enabling detailed calculations of electronic properties like the Hall coefficient and vortex lattice geometry, and explains experimental observations through band structure adjustments.

Contribution

It introduces precise tight-binding models for SrRuO3 and Sr2RuO4 that facilitate efficient and accurate calculations of electronic transport and superconducting properties.

Findings

The tight-binding Hamiltonians match full-potential band structures accurately.

The Hall coefficient sign reversal can be explained by band shifts and relaxation time variations.

The models enable detailed analysis of vortex lattice geometry and anisotropy in Sr2RuO4.

Abstract

Accurate orthogonal tight-binding Hamiltonians are constructed for ferromagnetic SrRuO$_3$ and the layered perovskite superconductor, Sr$_2$RuO$_4$ by fitting to all-electron full-potential local density band structures obtained by the linearized augmented planewave method. These Hamiltonians allow the band structure to be computed on very fine meshes in the Brillouin zone at low cost, and additionally have analytic band velocities, while retaining the accuracy of the full-potential electronic structure calculations. This greatly facilitates calculation of transport and superconducting parameters related to the fermiology. These features are exploited to calculate the Hall coefficient and vortex lattice geometry for Sr$_2$RuO$_4$ with fine integration meshes. We find the lower limit for the interband order parameter anisotropy to be compatible with the observed square geometry. We also find that the sign reversal of the Hall coefficient can be explained in a conventional way if the bands are shifted by a few mRy so as to match the experimental de Haas-van Alphen areas exactly, {\it and} the temperature dependence of the relaxation time is strongly dependent on the band character.