title: Candidate quantum spin liquid due to dimensional reduction of a two-dimensional honeycomb lattice.
abstract: As with quantum spin liquids based on two-dimensional triangular and kagome lattices, the two-dimensional honeycomb lattice with either a strong spin-orbital coupling or a frustrating second-nearest-neighbor coupling is expected to be a source of candidate quantum spin liquids. An ammonium salt [(C3H7)3NH]2[Cu2(C2O4)3](H2O)2.2 containing hexagonal layers of Cu(2+) was obtained from solution. No structural transition or long-range magnetic ordering was observed from 290 K to 2 K from single crystal X-ray diffraction, specific heat and susceptibility measurements. The anionic layers are separated by sheets of ammonium and H2O with distance of 3.5 Å and no significant interaction between anionic layers. The two-dimensional honeycomb lattice is constructed from Jahn-Teller distorted Cu(2+) and oxalate anions, showing a strong antiferromagnetic interaction between S = 1/2 metal atoms with θ = -120 (1) K. Orbital analysis of the Cu(2+) interactions through the oxalate-bridges suggests a stripe mode pattern of coupling with weak ferromagnetic interaction along the b axis, and strong antiferromagnetic interaction along the a axis. Analysis of the magnetic susceptibility shows that it is dominated by a quasi-one-dimensional contribution with spin chains that are at least as well isolated as those of well-known quasi-one-dimensional spin liquids.
authors.affiliation: Organic Solid Laboratory, BNLMS, CMS &Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Institute of Condensed Matter Physics, College of Physics, Peking University, Beijing, 100871, P. R. China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: BNLMS, College of Chemical and Molecular Engineering, Peking University, 100871, P. R. China.
authors.forename: Zheming
authors.initials: Z
authors.lastname: Wang
authors.affiliation: National Center for Nanoscience and Nanotechnology, Beijing, 100190, P. R. China.
authors.forename: Dongwei
authors.initials: D
authors.lastname: Wang
authors.affiliation: ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, OX11 0QX, United Kingdom.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Baker
authors.affiliation: ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, OX11 0QX, United Kingdom.
authors.forename: Francis L
authors.initials: FL
authors.lastname: Pratt
authors.affiliation: Organic Solid Laboratory, BNLMS, CMS &Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.
authors.forename: Daoben
authors.initials: D
authors.lastname: Zhu