Magnetism and superconductivity in doped triangular-lattice Mott insulators

TL;DR

This paper investigates the interplay of magnetism and superconductivity in doped triangular-lattice Mott insulators using an extended Hubbard model, revealing a complex phase diagram with competing and coexisting orders.

Contribution

It introduces a comprehensive extended Hubbard model on a triangular lattice to explore magnetic and superconducting phases, including coexistence and phase transitions.

Findings

Rich phase diagram with various magnetic orders and pairing states

Identification of nesting vectors and Lifshitz transition

Coexistence of magnetism and triplet superconductivity

Abstract

Inspired by recent advances in the fabrication of surface superlattices, and in particular the triangular lattice made of tin (Sn) atoms on silicon, we study an extended Hubbard mode on a triangular lattice. The observations of magnetism in these systems justify the inclusion of a strong on-site repulsion and the observation of superconductivity suggests including an effective, nearest-neighbor attractive interaction. The attractive interaction mimics the effect of strong on-site repulsion near half filling, which can be seen in strong coupling vertex calculations such as the Eliashberg method. With this extended Hubbard model on a triangular lattice with its geometrical frustration, we find a rich phase diagram of various magnetic orders and pairing functions, within the framework of self-consistent mean field theory. We uncover the competition among magnetism and unconventional superconductivity, and their coexistence for triplet pairings. We follow the Fermi surface of the system as the system is doped away from half filling and find nesting vectors and a Lifshitz transition which provide an intuitive understanding of the phase transitions between the many orders we consider.