Nature of extrinsic and intrinsic self-trapping of charge carriers in underdoped cuprate high-T_c superconductors

Abstract

Nature of extrinsic and intrinsic self-trapping (ST) of charge carriers in cuprates have been studied theoretically. The binding energies and radii of the extrinsic and intrinsic large polarons and bipolarons in cuprates are calculated variationally using the continuum model and adiabatic approximation. We have shown that the extrinsic and intrinsic three-dimensional (3D) large bipolarons exist in underdoped cuprates at η=ε_∞/ε_0<0.127 and η<0.138, respectively [where ε_∞ (ε_0) is the optic (static) dielectric constant].

Keywords

• polaron
• bipolaron
• self-trapping
• high-Tc superconductors
• high-T_c superconductors