Tunneling driven tilt modes of the O octahedra in La{2-x}Sr{x}CuO{4}: strong dependence on doping

TL;DR

This study investigates how doping affects lattice fluctuations related to tunneling tilt modes of oxygen octahedra in La{2-x}Sr{x}CuO{4}, revealing significant changes in transition rates and relaxation strength with Sr doping.

Contribution

It provides new insights into the doping dependence of tunneling-driven tilt modes and their coupling with hole excitations in La{2-x}Sr{x}CuO{4}.

Findings

Doping drastically increases transition rates of tilt modes.

Relaxation strength of tunneling systems is significantly enhanced by Sr doping.

Fast temperature dependence of relaxation rates cannot be explained by standard models.

Abstract

The anelastic spectrum of La{2-x}Sr{x}CuO{4} (x = 0, 0.008, 0.019, 0.032) has been measured down to 1.5 K, in order to see the effect of doping on the intrinsic lattice fluctuations already found in stoichiometric La{2}CuO{4}, and identified with tunneling driven tilt modes of the O octahedra. Slight doping with Sr causes a drastic increase of the transition rates and relaxation strength of the tunneling systems. The influence of doping on the relaxation rate is interpreted in terms of direct coupling between between the tilts of the octahedra and the hole excitations. However, the observed fast dependence of the rate on temperature cannot be explained in terms of the ususal models of coupling between a tunneling system and the conduction electrons.