Orain J-C, Bernu B, Mendels P, Clark L, Aidoudi F H, Lightfoot P, Morris R E, Bert F
Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France.
Laboratory for Muon Spin Spectroscopy, Paul Scherrer Insititut, 5232 Villigen PSI, Switzerland.
Phys Rev Lett. 2017 Jun 9;118(23):237203. doi: 10.1103/PhysRevLett.118.237203.
In the vanadium oxyfluoride compound (NH_{4}){2}[C{7}H_{14}N][V_{7}O_{6}F_{18}] (DQVOF), the V^{4+} (3d^{1}, S=1/2) ions realize a unique, highly frustrated breathing kagome lattice composed of alternately sized, corner-sharing equilateral triangles. Here we present an ^{17}O NMR study of DQVOF, which isolates the local susceptibility of the breathing kagome network. By a fit to series expansion, we extract the ratio of the interactions within the breathing kagome plane, J_{∇}/J_{Δ}=0.55(4), and the mean antiferromagnetic interaction J[over ¯]=60(7) K. Spin lattice (T_{1}) measurements reveal an essentially gapless excitation spectrum with a maximum gap Δ/J[over ¯]=0.007(7). Our study provides new impetus for further theoretical investigations in order to establish whether the gapless spin liquid behavior displayed by DQVOF is intrinsic to its breathing kagome lattice or whether it is due to perturbations to this model, such as a residual coupling of the V^{4+} ions in the breathing kagome planes to the interlayer V^{3+} (S=1) spins.
在钒氧氟化合物(NH₄)₂[C₇H₁₄N]V₇O₆F₁₈中，V⁴⁺(3d¹，S = 1/2)离子形成了一个独特的、高度受挫的呼吸式 Kagome 晶格，该晶格由大小交替的、角共享的等边三角形组成。在此，我们展示了对 DQVOF 的¹⁷O NMR 研究，该研究分离出了呼吸式 Kagome 网络的局部磁化率。通过对级数展开的拟合，我们提取出呼吸式 Kagome 平面内相互作用的比值 J₇/J₈ = 0.55(4)，以及平均反铁磁相互作用 J̅ = 60(7) K。自旋晶格(T₁)测量揭示了一个基本上无隙的激发谱，最大能隙 Δ/J̅ = 0.007(7)。我们的研究为进一步的理论研究提供了新的动力，以便确定 DQVOF 所展示的无隙自旋液体行为是其呼吸式 Kagome 晶格所固有的，还是由于对该模型的扰动，例如呼吸式 Kagome 平面中的 V⁴⁺离子与层间 V³⁺(S = 1)自旋的残余耦合。
