2024-03-28T17:40:31Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/1399352017-12-18T14:32:13Zcom_10261_14181com_10261_4col_10261_14182
Esteve, J.G.
Sierra, Germán
2016-11-08T10:04:42Z
2016-11-08T10:04:42Z
1995-04-01
Physical Review B 51: 8928- 8938 (1995)
http://hdl.handle.net/10261/139935
10.1103/PhysRevB.51.8928
We propose a method to construct the ground state ψ(λ) of local lattice Hamiltonians with the generic form H0+λH1, where λ is a coupling constant and H0 is a Hamiltonian with a nondegenerate ground state ψ0. The method is based on the choice of an exponential ansatz ψ(λ)=exp[U(λ)]ψ0, which is a sort of generalized lattice version of a Jastrow wave function. We combine perturbative and variational techniques to get successive approximations of the operator U(λ). Perturbation theory is used to set up a variational method which in turn produces nonperturbative results. The computation with this kind of ansatz leads us to associate to the original quantum-mechanical problem a statistical-mechanical system defined in the same spatial dimension. In some cases these statistical-mechanical systems turn out to be integrable, which allows us to obtain exact upper bounds to the energy. The general ideas of our method are illustrated in the example of the Ising model in a transverse field. © 1995 The American Physical Society.
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A perturbative and variational approach to quantum lattice Hamiltonians
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