Anelastic relaxation process of polaronic origin inLa2−xSrxCuO4: Interaction between charge stripes and pinning centers

Abstract

The evolution of an anelastic relaxation process occurring around 80 K in ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ at a measuring frequency of $\ensuremath{\sim}1\mathrm{kHz}$ has been followed from $x=0.0075$ to the overdoped region $x=0.2,$ where it disappears. The dependence of the peak intensity on doping is consistent with a polaronic mechanism, identified with the disordered charge stripes overcoming pinning centers. A marked decrease of the peak amplitude and of the effective energy barrier for relaxation occurs at $x>0.045,$ the same doping range where a change of the stripe order from parallel to diagonal with respect to the Cu-O bonds has been observed by neutron diffraction. Both the energy barrier and peak amplitude also exhibit a rise near $x=1/8.$