Pairing symmetries in the Zeeman-coupled extended attractive Hubbard model

TL;DR

This paper explores the extended attractive Hubbard model with mixed pairing symmetries, revealing a rich phase diagram and the dominance of non-unitary triplet order under magnetic fields, advancing understanding of superconductivity.

Contribution

It introduces a comprehensive analysis of pairing symmetries in the EAHM using HFBdG and d-vector formalism, highlighting the dominance of triplet order and phase transitions driven by electron density.

Findings

Non-unitary triplet order dominates under in-plane magnetic field.

Transition from non-unitary to unitary superconducting phase with electron density change.

EAHM effectively models various pairing symmetries in superconductors.

Abstract

By introducing the possibility of equal- and opposite-spin pairings concurrently, we show that the extended attractive Hubbard model (EAHM) exhibits rich ground state phase diagrams with a variety of singlet, triplet, and mixed parity superconducting orders. We study the competition between these superconducting pairing symmetries invoking an unrestricted Hartree-Fock- Bogoliubov-de Gennes (HFBdG) mean-field approach, and we use the d-vector formalism to characterize the nature of the stabilized superconducting orders. We discover that, while all other types of orders are suppressed, a non-unitary triplet order dominates the phase space in the presence of an in-plane external magnetic field. We also find a transition between a non-unitary to unitary superconducting phase driven by the change in average electron density. Our results serve as a reference for identifying and understanding the nature of superconductivity based on the symmetries of the pairing correlations. The results further highlight that EAHM is a suitable effective model for describing most of the pairing symmetries discovered in different materials.