Magnetism and topological phases in an interacting decorated honeycomb lattice with spin-orbit coupling

TL;DR

This paper explores how spin-orbit coupling and Coulomb interactions influence various quantum phases in a decorated honeycomb lattice, revealing novel topological and magnetic states.

Contribution

It uncovers the phase diagram showing the stability of quantum spin Hall insulators, semimetallic phases, and RVB spin liquids under different interaction strengths and SOC.

Findings

Quantum spin Hall insulator stable at weak Coulomb and moderate SOC

Emergence of a topologically non-trivial semimetal at large SOC

Coulomb interactions stabilize a resonating valence bond spin liquid

Abstract

We study the interplay between spin-orbit coupling (SOC) and Coulomb repulsion in a Hubbard model on a decorated honeycomb lattice which leads to a plethora of phases. While a quantum spin hall insulator is stable at weak Coulomb repulsion and moderate SOC, a semimetallic phase emerges at large SOC in a broad range of Coulomb repulsion. This semimetallic phase has topological properties not observed in conventional metals such as a finite, non-quantized spin Hall conductivity. At large Coulomb repulsion and negligible spin-orbit coupling, electronic correlations stabilize a resonance valence bond (RVB) spin liquid state in contrast to the classical antiferromagnetic state predicted by mean-field theory. Under sufficiently strong SOC, such RVB state is transformed into a magnetic insulator consisting on S~3/2 localized moments on a honeycomb lattice with antiferromagnetic order and topological features.