The composite picture of the charge carriers in La2−xSrxCuO4 (0.063 ≤ x ≤ 0.11) superconductors

Through far-infrared studies of La2-xSrxCoU4 single crystals for x = 0.063, 0.07, 0.09, and 0.11, we found that only similar to0.2% of the total holes participated in the nearly dissipationless normal state charge transport and superconductivity. We have also observed characteristic collective modes at omega similar to 18 and 22 cm(-1) due to the bound carriers in an electronic lattice (EL) state, and the free carriers are massively screened by the EL. Our findings lead us to propose a composite picture of the charge system where the free carriers are coupled to and riding on the EL. This unique composite system of charge carriers may provide further insights into the understanding of the cuprate physics.