Herbertsmithite, ZnCu3(OH)6Cl2, is a two dimensional kagome lattice realization of a spin liquid, with evidence for fractionalized excitations and a gapped ground state. Such a quantum spin liquid has been proposed to underlie high temperature superconductivity and is predicted to produce a wealth of new states, including a Dirac metal at 1/3rd electron doping. Here we report the topochemical synthesis of electron doped ZnLixCu3(OH)6Cl2 from x = 0 to x = 1.8 (3/5th per Cu2+). Intercalation of Li ions is achieved through exposing herbertsmithite to a reducing solution of benzophenone and lithium under precise conditions. To obtain lower doping concentrations, the fully doped sample is systematically deintercalated by iodine in acetonitrile. X-ray diffraction studies demonstrate the underlying kagome structure of the doped herbertsmithite series is maintained, while X-ray photoelectron spectroscopy shows a change in the oxidation state and local chemical environment of the copper. This is consistent with a reduction of the copper kagome layer. Contrary to expectations, no metallicity or superconductivity is induced. Instead, we find a systematic suppression of magnetic behavior across the phase diagram. Our results demonstrate that significant theoretical work is needed to understand and predict the role of doping in magnetically frustrated narrow band insulators, particularly the interplay between local structural disorder and tendency toward electron localization, and pave the way for future studies of doped spin liquids.

Electron doping a kagome spin liquid

253rd National Meeting (2017)

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