Quasi-particle density of states and bosonic modes in Bi2Sr2CaCu2O[formula omitted

Abstract

The quasi-particle density of states (DOS) at temperatures from 4.2 K to high above the critical temperature Tc is obtained by inversion directly from the experimentally measured superconductor-insulator-superconductor (SIS) tunneling data performed on three different Bi2Sr2CaCu2O8+δ samples. Bosonic modes accompanying the superconductivity or related to the pseudogap, as well as their temperature-dependent energies are extracted by analyzing the fine structures exhibited in the DOS curves. Consistent with the coexistence of the two bosonic modes in the superconducting state for the optimally and underdoped samples, a kink is found in the derivative curve of the DOS with respect to the energy, which provides a kind of evidence for the coexistence of the pseudogap and superconductivity in these materials. These results shed light on the interactions between the charged carriers and the bosonic modes and may give us the fingerprints of the pairing gluons in the cuprates.