Herbertsmithite, ZnCu 3 ðOHÞ 6 Cl 2 , 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=3 electron doping. Here, we report the topochemical synthesis of electrondoped ZnLi x Cu 3 ðOHÞ 6 Cl 2 from x ¼ 0 to x ¼ 1.8 (3=5 per Cu 2þ ). 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.

Synthetic barlowite, Cu 4 (OH) 6 BrF, has emerged as a new quantum spin liquid (QSL) host, containing kagomé layers of S=1/2 Cu 2+ ions separated by interlayer Cu 2+ ions. Similar to synthetic herbertsmithite, ZnCu 3 (OH) 6 Cl 2 , it has been reported that Zn 2+ substitution for the interlayer Cu 2+ induces a QSL ground state. Here we report a scalable synthesis of single crystals of Cu 4 (OH) 6 BrF. Through x-ray, neutron, and electron diffraction measurements coupled with magic angle spinning 19 F and 1 H NMR spectroscopy, we resolve the previously reported positional disorder of the interlayer Cu 2+ ions and find that the structure is best described in the orthorhombic space group, Cmcm, with lattice parameters a = 6.665(13) Å, b = 11.521(2) Å, c = 9.256(18) Å and an ordered arrangement of interlayer Cu 2+ ions. Infrared spectroscopy measurements of the O-H and F-H stretching frequencies demonstrate that the orthorhombic symmetry persists upon substitution of Zn 2+ for Cu 2+ . Specific heat and magnetic susceptibility measurements of Znsubstituted barlowite, Zn x Cu 4-x (OH) 6 BrF, reveal striking similarities with the behavior of Zn x Cu 4-x (OH) 6 Cl 2 . These parallels imply universal behavior of copper kagomé lattices even in the presence of small symmetry breaking distortions. Thus synthetic barlowite demonstrates universality of the physics of synthetic Cu 2+ kagomé minerals and furthers the development of real QSL states.

We report the successful crystal growth of a previously unknown mixed-metal organic compound (CH3NH3)2AgInBr6.