Topological strongly correlated phases in orthorhombic diamond lattice compounds

TL;DR

This paper investigates the topological and strongly correlated phases in orthorhombic diamond lattice compounds, revealing a transition from semimetal to a quantum spin liquid Mott insulator with topological features, relevant to experimental molecular materials.

Contribution

It extends slave-rotor mean-field theory to include magnetic order, uncovering a topological quantum spin liquid phase in the Mott transition of orthorhombic diamond lattices.

Findings

Identifies a transition from semimetal to Mott insulator at critical U_c.

Discovers a U(1) quantum spin liquid phase with topological nodal structures.

Shows how Green's function zeros reflect spinon band topology.

Abstract

We explore the Mott transition in orthorhombic diamond lattices relevant to (ET)Ag$_4$(CN)$_5$ molecular compounds. The non-interacting phases include nodal line, Dirac and/or Weyl semimetals depending on the strength of spin-orbit coupling and the degree of dimerization of the lattice. Based on an extension of slave-rotor mean-field theory which accounts for magnetic order, we find a transition from a semimetal to a paramagnetic Mott insulator at a critical $U_c$ which becomes N\'eel ordered at a larger Coulomb repulsion, $U_{cm}>U_{c}$. The resulting intermediate Mott phase is a $U(1)$ quantum spin liquid (QSL) consisting on spinon preserving the nodal structure of the nearby semimetallic phases. An analysis of the Green's function in this Mott phase shows how the zeros follow the spinon band dispersions carrying the topology while the poles describe the Hubbard bands. Our results are relevant to recent observations in (ET)Ag$_4$(CN)$_5$ molecular compounds in which the ambient pressure N\'eel ordered Mott insulator is gradually suppressed until semimetallic behavior arises at larger pressures.