Coexistence of spin-triplet superconductivity with magnetism within a single mechanism for orbitally degenerate correlated electrons: Statistically-consistent Gutzwiller approximation

TL;DR

This paper investigates a two-band Hubbard model with orbitally degenerate electrons, analyzing the coexistence of spin-triplet superconductivity and magnetism using the statistically consistent Gutzwiller approximation, and compares it with Hartree-Fock results.

Contribution

It introduces a detailed analysis of coexisting magnetic and spin-triplet superconducting states within a correlated electron model using SGA, highlighting differences from traditional HF+BCS methods.

Findings

SGA predicts different stability regions for phases compared to HF+BCS.

Coexistence of magnetism and spin-triplet superconductivity is stabilized by Hund's coupling.

Inter-site hybridization influences the stability of paired phases.

Abstract

An orbitally degenerate two-band Hubbard model is analyzed with inclusion of the Hund's rule induced spin-triplet paired states and their coexistence with magnetic ordering. The so-called statistically consistent Gutzwiller approximation (SGA) has been applied to the case of a square lattice. The superconducting gaps, the magnetic moment, and the free energy are analyzed as a function of the Hund's rule coupling strength and the band filling. Also, the influence of the intersite hybridization on the stability of paired phases is discussed. In order to examine the effect of correlations the results are compared with those calculated earlier within the Hartree-Fock (HF) approximation combined with the Bardeen-Cooper-Schrieffer (BCS) approach. Significant differences between the two used methods (HF+BCS vs. SGA+real-space pairing) appear in the stability regions of the considered phases. Our results supplement the analysis of this canonical model used widely in the discussions of pure magnetic phases with the detailed elaboration of the stability of the spin-triplet superconducting states and the coexistent magnetic-superconducting states. At the end, we briefly discuss qualitatively the factors that need to be included for a detailed quantitative comparison with the corresponding experimental results.