Lattice effects in the La$_{\rm 2-x}$Sr$_{\rm x}$CuO$_{\rm 4}$ compounds

TL;DR

This study investigates how doping affects lattice distortions and phase separation in La$_{2-x}$Sr$_x$CuO$_4$, revealing a coupling between spin/charge ordering and lattice effects across all doping levels.

Contribution

It provides the first systematic Raman analysis of doping-induced lattice effects and their relation to spin and charge ordering in La$_{2-x}$Sr$_x$CuO$_4$.

Findings

Doping modifies Raman spectra indicating lattice distortions.

Spin and charge orderings are coupled with lattice effects.

Lattice effects persist across all doping levels.

Abstract

Systematic Raman studies on several cuprates (YBa$_{\rm 2}$Cu$_{\rm 3}$O$_{\rm x}$, YBa$_{\rm 2}$Cu$_{\rm 4}$O$_{\rm 8}$ or Bi$_{\rm 2}$Sr$_{\rm 2}$CaCu$_{\rm 2}$O$_{\rm 8}$) have shown that at optimal doping the compounds are at the edge of lattice instability; once this level is exceeded, by means of doping or applying external hydrostatic pressure, the changes in the transition temperature are accompanied by spectral modifications. There are strong indications that the reduction in T$_{\rm c}$ is correlated with a separation into nanoscale phases, which involve the oxygen atoms of the CuO$_{\rm 2}$ planes. In this work, modifications with doping in the Raman spectra of the La$_{\rm 2-x}$Sr$_{\rm x}$CuO$_{\rm 4}$ compound are presented, which show that spin or charge ordering is coupled with lattice distortions in the whole doping region.