Dzyaloshinskii-Moriya anisotropy and non-magnetic impurities in the $s=1/2$ kagome system ZnCu_3(OH)_6Cl_2

Abstract

Motivated by recent nuclear magnetic resonance experiments on ZnCu${}_3$(OH)${}_6$Cl${}_2$, we present an exact-diagonalization study of the combined effects of non-magnetic impurities and Dzyaloshinskii-Moriya (DM) interactions in the $s=1/2$ kagome antiferromagnet. The local response to an applied field and correlation-matrix data reveal that the dimer freezing which occurs around each impurity for $D=0$ persists at least up to $D/J\simeq 0.06$, where $J$ and $D$ denote respectively the exchange and DM interaction energies. The phase transition to the ($Q=0$) semiclassical, 120${}^{\circ }$ state favored at large $D$ takes place at $D/J\simeq 0.1$. However, the dimers next to the impurity sites remain strong up to values $D\sim J$, far above this critical point, and thus do not participate fully in the ordered state. We discuss the implications of our results for experiments on ZnCu${}_3$(OH)${}_6$Cl${}_2$.

11 pages, submitted to PRB

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Cited by in corpus (2)

• Quantum criticality of the kagome antiferromagnet with Dzyaloshinskii-Moriya interactions
• Impurity-doped Kagome Antiferromagnet: A Quantum Dimer Model Approach