Phys. Rev. B 45, 4877 (1992)

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Variational description of a quasihole excitation in a quantum antiferromagnet

Massimo Boninsegni and Efstratios Manousakis

Department of Physics, Center for Materials Research and Technology Supercomputer Computations Research Institute, Florida State University, Tallahassee, Florida 32306

An accurate variational ansatz is proposed for a single quasihole excitation in a two-dimensional quantum antiferromagnet. The trial state includes spin-hole and spin-hole-spin correlations, in addition to background antiferromagnetic spin-spin correlations. Background spin-spin correlations are induced by the Heisenberg antiferromagnetic exchange interaction and describe the zero-point motion of spin waves around the Néel state. Spin-hole and spin-hole correlations describe ``strings'' of spins displaced by one lattice site along the hole path. This is a generalization of the Brinkman-Rice approach to include quantum spin fluctuations. We have used the Monte Carlo method to compute the variational energy and the spectral weight of the quasihole state in the t-J model on the square lattice, with the proposed ansatz. Comparison with exact results for the 4 x 4 lattice shows very good agreement for both energy and spectral weight, at k=( pi /2, pi /2) in the range 0 <= t/J <= 5. We report results for lattices of several sizes up to 16 x 16 in the above range of t/J and for the two values of k where the hole energy band attains its minimum [k=( pi /2, pi /2)] and maximum [k=(0,0)].

©1992 The American Physical Society.

PACS: 74.20.-z 75.10.Jm 74.65.+n

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