Different roles of Zn${}^{2+}$ and Li${}^{+}$ impurities in the CuO${}_2$ plane in undoped cuprate compounds

Abstract

A planar Mott insulator with easy plane Néel order can be mapped onto a Gutzwiller-projected spin Hall state. The in-plane substitution of Zn${}^{2+}$ and Li${}^{+}$ for Cu${}^{2+}$ brings zero modes around the spin vacancy. The Gutzwiller projection precludes single particle excitations, however, preserves the zero modes which have a local spin moment for Zn${}^{2+}$ and a local charged hole for Li${}^{+}$, respectively. While the local spin moment for Zn${}^{2+}$ is screened by the long-range spin correlations, the active charge degree of freedom for Li${}^{+}$ impurity twists the spin background with long ranged disturbances. This proposal explains the very different roles of the Zn${}^{2+}$ and Li${}^{+}$ impurities on the magnetic perturbations in the CuO${}_2$ plane in the undoped cuprate compounds.

5 pages, 6 figures