Quantum spin liquid states in the two dimensional kagome antiferromagnets, ZnxCu4-x(OD)6Cl2

摘要: A three-dimensional system of interacting spins typically develops static long-range order when it is cooled. If the are quantum (S = 1/2), however, novel paramagnetic states may appear. The most highly sought state among them resonating valence bond (RVB) in which every pair neighboring form entangled spin singlets (valence bonds) and mechanically amongst all possible degenerate pairing states. Here we provide experimental evidence for such existing frustrated antiferromagnets, ZnxCu4-x(OD)6Cl2, where S 1/2 magnetic Cu2+ moments layers a two-dimensional kagome lattice. We find that Cu4(OD)6Cl2, distorted planes weakly coupled to each other, dispersionless excitation mode appears spectrum below ~ 20 K, whose characteristics resemble those solid state, known as (VBS), breaks translational symmetry. Doping nonmagnetic Zn2+ ions reduces distortion lattice, weakens interplane coupling but also dilutes occupancy VBS suppressed ZnCu3(OD)6Cl2 undistorted 90% occupied by ions, low energy fluctuations liquid phase become featureless.