Metal-insulator transition and antiferromagnetism in the ground state of the Hubbard model

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Abstract
A new trial function describing the ground state of the Mott antiferromagnetic insulator in the framework of the Hubbard model is proposed. The case under consideration gives a nontrivial of the exactly soluble nonorthogonality problem. The possibility of describing the antiferromagnetic state without anomalous averages is explicitly demonstrated. The extension of the trial function to the metallic phase leads to the conclusion that the metal-insulator transition in the ground state of the Hubbard model is the first-order transition from an antiferromagnetic insulator to a paramagnetic or antiferromagnetic metal. Considering the effect of alternating electric field on their trail function, the authors investigate the optical properties of the Mott insulator.