期刊
PHYSICAL REVIEW B
卷 78, 期 23, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.78.235120
关键词
electron-phonon interactions; ground states
We generalize the momentum average (MA) approximation to study the properties of models with g(q) momentum-dependent electron-phonon coupling. As in the case of the application of the original MA to the Holstein model, the results are analytical, numerically trivial to evaluate, exact for both zero bandwidth and for zero electron-phonon coupling, and accurate everywhere in parameter space. Comparison with available numerical data confirms this accuracy. We then show that further improvements can be obtained based on variational considerations using the one-dimensional breathing-mode Hamiltonian as a specific example. For example, by using this variational MA, we obtain ground-state energies within at most 0.3% error of the numerical data.
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