Wigner Crystallization in ${\mathrm{N}\mathrm{a}}_{3}{\mathrm{C}\mathrm{u}}_{2}{\mathrm{O}}_{4}$ and ${\mathrm{N}\mathrm{a}}_{8}{\mathrm{C}\mathrm{u}}_{5}{\mathrm{O}}_{10}$ Chain Compounds

Wigner Crystallization in ${N a}_{3} {C u}_{2} O_{4}$ and ${N a}_{8} {C u}_{5} O_{10}$ Chain Compounds

P. Horsch, M. Sofin, M. Mayr, and M. Jansen

Phys. Rev. Lett. 94, 076403 – Published 23 February 2005

Abstract

We report the synthesis of novel edge-sharing chain systems ${N a}_{3} {C u}_{2} O_{4}$ and ${N a}_{8} {C u}_{5} O_{10}$ , which form insulating states with commensurate charge order. We identify these systems as one-dimensional Wigner lattices, where the charge order is determined by long-range Coulomb interaction and the number of holes in the $d$ shell of Cu. Our interpretation is supported by x-ray structure data as well as by an analysis of magnetic susceptibility and specific heat data. Remarkably, due to large second neighbor Cu-Cu hopping, these systems allow for a distinction between the (classical) Wigner lattice and the $4 k_{F}$ charge-density wave of quantum mechanical origin.