Optimal Boson energy for superconductivity in the Holstein model
arXiv:1602.08351 · doi:10.1103/PhysRevB.93.224501
Abstract
We examine the superconducting solution in the Holstein model, where the conduction electrons couple to the dispersionless Boson fields, using the Migdal-Eliashberg theory and Dynamical Mean Field Theory. Although different in numerical values, both methods imply the existence of an optimal Boson energy for superconductivity at a given electron-Boson coupling. This non-monotonous behavior can be understood as an interplay between the polaron and superconducting physics, as the electron-Boson coupling is the origin of the superconductor, but at the same time traps the conduction electrons making the system more insulating. Our calculation provides a simple explanation on the recent experiment on sulfur hydride (HS), where an optimal pressure for the superconductivity was observed. The validities of both methods are discussed.
5 figures, 11 pages, single column
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