Doping evolution of the phonon density of states and electron-lattice interaction in Nd₂₋ₓCeₓCuO₄₊δ

Original · EN

We use inelastic neutron scattering to study the evolution of the generalized phonon density of states (GDOS) of the n-type high-Tc superconductor Nd₂₋ₓCeₓCuO₄₊δ (NCCO), from the half-filled Mott-insulator (x=0) to the Tc=24 K superconductor (x=0.15). Upon doping the CuO₂ planes in Nd₂CuO₄₊δ (NCO) with electrons by Ce substitution, the most significant change in the GDOS is the softening of the highest phonon branches associated with the Cu-O bond stretching and out-of-plane oxygen vibration modes. However, the softening occurs within the first few percent of Ce-doping and is not related to the electron doping induced nonsuperconducting-superconducting transition (NST) at x≈ 0.12. These results suggest that the electron-lattice coupling in the n-type high-Tc superconductors is different from that in the p-type materials.