Smectic and nematic phase modulations and transitions under electron beam in Tb2Cu0.83Pd0.17O4

Abstract

Understanding the structural origin of the functionality in cuprates has attracted tremendous attention over several decades. In particular, probing distortions in the Cu-O bonding is of great importance for exploring the coupling between the charge and the lattice, a key mechanism for superconductivity and other functionality in correlated materials. Here we study a superlattice modulation in the ${\mathrm{Tb}}_{2}{\mathrm{Cu}}_{0.83}{\mathrm{Pd}}_{0.17}{\mathrm{O}}_{4}$ ``214'' material, which possesses no superconductivity itself but has the parent structure of the ${R}_{2}{\mathrm{CuO}}_{4}$ (R = a rare-earth element) superconducting cuprate group. Using transmission electron microscopy (TEM), we find that this superlattice modulation is formed by Cu ion displacements in a direction perpendicular to the Cu-O planes. The superlattice modulation undergoes a reversible electronic smectic-nematic phase transition under electron-beam illumination. With the help of in situ TEM results, our findings imply that the superlattice modulation in this material arises from spatially modulated charge ordering at the Cu sites.