Chronological - Ordering method applied to calculation of polaron free- and ground-state energies

L. F. Lemmens, J. T. Devreese

K. Wang, Qing‐Hu Chen, Shaolong Wan

Ward Huybrechts

John T. Marshall, M. S. Chawla

In the expansion of the ground-state energy of a polaron in a weak magnetic field, the zeroth-order term is the polaron self-energy, while the first-order term is inversely proportional to the polaron effective mass. The effective mass so obtained is exactly equivalent to the freepolaron effective mass as defined by Fr\"ohlich. This equivalence principle is used to approximate the polaron effective mass by employing an approximate expression for the ground-state energy of a polaron in a weak magnetic field obtained by applying Feynman's path-integral variational method. The resultant polaron effective mass is found to be higher than Feynman's result by less than 1%.

Xuezao Ren, Huang Shu-Wen, Liao Xu +2 more

Applying the method of coherent state orthogonal expansion, an analytical expression of the ground state energy for one-dimensional Holstein model is obtained. We expand the trial wave function of ground state to third order, and calculate the ground state energy for different lattice sites and different coupling intensities. In the third order approximation, the ground state energy agrees with the numerical solution.

N. N. Bogolyubov, Alexey N. Kireev, A. M. Kurbatov