Benchmark study of Nagaoka ferromagnetism by spin-adapted full configuration interaction quantum Monte Carlo

Abstract

We investigate Nagaoka ferromagnetism in the two-dimensional Hubbard model with one hole using the spin-adapted ($SU(2)$ conserving) full configuration interaction quantum Monte Carlo method. This methodology gives us access to the ground state energies of all possible spin states $S$ of finite Hubbard lattices, here obtained for lattices up to 24 sites, for various interaction strengths ($U$). The critical interaction strength, $U_c$, at which the Nagaoka transition occurs is determined for each lattice and is found to be proportional to the lattice size for the larger lattices. Below $U_c$ the overall ground states are found to favour the minimal total spin ($S=\frac{1}{2}$), and no intermediate spin state is found to be the overall ground state on lattices larger than 16 sites. However, at $U_c$, the energies of all the spin states are found to be nearly degenerate, implying that large fluctuations in total spin can be expected in the vicinity of the Nagaoka transition.

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Cited by in corpus (3)

• Combined unitary and symmetric group approach applied to low-dimensional spin systems
• Polaronic mechanism of Nagaoka ferromagnetism in Hubbard models
• Polaron-Depleton Transition in the Yrast Excitations of a One-Dimensional Bose Gas with a Mobile Impurity