Correlation of dopant-induced optical transitions with superconductivity in La2−xSrxCuO4−δ

Abstract

Optical data for a series of ${\mathrm{La}}_{2\mathrm{-}\mathrm{x}}$ ${\mathrm{Sr}}_{\mathrm{x}}$ ${\mathrm{CuO}}_{4\mathrm{-}\mathrm{\delta }}$ solid solutions from x=0 to x=0.30 reveal several structures, including a relatively intense, dopant-induced absorption band around 0.5 eV whose oscillator strength tracks the Meissner effect and $T_c$ measured on the same set of samples. The dopant-induced optical-transition–superconductivity correlation strongly supports an electronically driven superconductivity mechanism mediated by the 0.5-eV excitation.