The charge-density waves (CDW) in the framework Landau theory are visualized to manifest in complex $R\mathrm{Ni}{\mathrm{O}}_3$ ($R$ = rare-earth) nickelates in which the structure controls the incipient charge order in the weak localization limit. Any consequent effect demonstrating these nickelates in the rare category of CDW conductors with controlled charge-lattice interactions has been elusive so far. Employing terahertz time-domain spectroscopy along selective crystal axes, we present evidence of the CDW in epitaxial strain-modulated crystal structures of prototypical $\mathrm{NdNi}{\mathrm{O}}_3$. A finite peak structure at 5 meV in the terahertz conductivity displays all the characteristics of a CDW condensate in (110)- and (111)-oriented $\mathrm{NdNi}{\mathrm{O}}_3$ thin films. Contrasting charge dynamics of collective CDW mode and Drude conductivity emerging across dissimilar orientations helps disentangle charge ordering from the metal-insulator transition and establish a structure-property cause-effect relationship which may propose novel attributes in emerging oxide electronics.

• Received 1 May 2016
• Revised 20 December 2017

DOI:https://doi.org/10.1103/PhysRevB.97.045123