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Quantum spin liquid emerging in two-dimensional correlated Dirac fermions

2010; Nature Portfolio; Volume: 464; Issue: 7290 Linguagem: Inglês

10.1038/nature08942

1476-4687

Zi Yang Meng, Thomas C. Lang, Stefan Weßel, Fakher F. Assaad, A. Muramatsu,

Quantum many-body systems

At sufficiently low temperatures, condensed-matter systems tend to develop order. A notable exception to this behaviour is the case of quantum spin liquids, in which quantum fluctuations prevent a transition to an ordered state down to the lowest temperatures. There have now been tentative observations of such states in some two-dimensional organic compounds, yet quantum spin liquids remain elusive in microscopic two-dimensional models that are relevant to experiments. Here we show, by means of large-scale quantum Monte Carlo simulations of correlated fermions on a honeycomb lattice (a structure realized in, for example, 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: the possibility of unconventional superconductivity through doping therefore arises in our system. We foresee the experimental realization of this model system using ultra-cold atoms, or group IV elements arranged in honeycomb lattices. A quantum spin liquid is a hypothetical system of spins (such as those carried by electrons), the orientations of which continue to fluctuate even at absolute zero. The evidence for the existence of such states remains tentative. Zi Yang Meng et al. have developed a microscopic model of correlated electrons arranged on a honeycomb lattice (like that in, for example, graphene), and identify the conditions under which a quantum spin liquid is realized in such a system. This unexpected state of matter is a resonating valence bond state, akin to that proposed for high-temperature superconductors, raising the possibility of unconventional superconductivity through doping. A quantum spin liquid is a hypothetical system of spins (such as those carried by electrons), the orientations of which continue to fluctuate even at absolute zero. Theoretical and experimental evidence for the existence of such states at the microscopic level is elusive, but these authors have modelled correlated electrons arranged on a honeycomb lattice (such as in graphene), and identified the conditions under which a microscopic quantum spin liquid would be realized in two dimensions.