Quantum spin-liquid emerging in two-dimensional correlated Dirac fermions

TL;DR

This paper demonstrates through large-scale quantum Monte Carlo simulations that a quantum spin-liquid state can emerge in two-dimensional correlated Dirac fermions on the honeycomb lattice, revealing a potential pathway to unconventional superconductivity.

Contribution

The study provides the first numerical evidence of a quantum spin-liquid phase in a microscopic two-dimensional model with Dirac fermions, bridging a gap between theory and experimental realization.

Findings

Quantum spin-liquid appears between Dirac fermion and antiferromagnetic phases.

The spin-liquid is a short-range resonating valence bond state.

Potential for unconventional superconductivity upon doping.

Abstract

At sufficiently low temperatures, condensed-matter systems tend to develop order. An exception are quantum spin-liquids, where fluctuations prevent a transition to an ordered state down to the lowest temperatures. While such states are possibly realized in two-dimensional organic compounds, they have remained elusive in experimentally relevant microscopic two-dimensional models. Here, we show by means of large-scale quantum Monte Carlo simulations of correlated fermions on the honeycomb lattice, a structure realized in graphene, that a quantum spin-liquid emerges between the state described by massless Dirac fermions and an antiferromagnetically ordered Mott insulator. This unexpected quantum-disordered state is found to be a short-range resonating valence bond liquid, akin to the one proposed for high temperature superconductors. Therefore, the possibility of unconventional superconductivity through doping arises. We foresee its realization with ultra-cold atoms or with honeycomb lattices made with group IV elements.