The strength of frustration and quantum fluctuations in LiVCuO ₄

Abstract

-We present an empirical and microscopical analysis of the main in-chain exchange constants of the edge-shared frustratrated chain cuprate LiVCuO4= LiCuVO4 with a ferromagnetic nearest neighbour coupling which clearly exceeds the antiferromagnetic (AFM) next-nearest neighbour exchange J2. The measured saturation field is significantly affected by a weak 3D AFM interchain coupling leaving room for a possible Bose-Einstein condensation for several T below. The obtained exchange parameters are in agreement with the results for a realistic five-band extended Hubbard Cu 3d O 2p model, LSDA+U predictions as well as with inelastic neutron and magnetization data. The single chain frustration rate α = J2/|J1| ≈ 0.75, including all error bars, is definitely smaller than 1.0 which correspond to strongly coupled interpenetrating AFM Heisenberg chains in contrast with opposite statements in the literature. A proper account of strong quantum fluctuations and frustration is necessary for a correct assignment of the exchange integrals. which cannot be achieved by a simple renormalization of J2 from spin-wave theory.

Interplay of interchain interactions and exchange anisotropy: Stability and fragility of multipolar states in spin-12quasi-one-dimensional frustrated helimagnets

“…An inspection of the phase diagrams reveals that the maximal value for the critical J IC always occurs in the nematic phase at α slightly below 1, i.e. in the region of maximal in-chain frustration and quantum behavior [26,28]. For the situation of perpendicular coupling this can be understood already in linear approximation, where j cr,1 is proportional to the difference of 1-and 2-magnon critical fields of an isolated chain j cr,1 = 2(h the saturation field tends to the simple 1-magnon value and additional quantum effects vanish.…”

Excitations and quasi-one-dimensionality in field-induced nematic and spin density wave states

“…Most recently, the spin-1/2 magnetic insulator LiCuVO 4 has emerged 22,23 as a promising candidate to realize both a high-field spin nematic phase, in a narrow region below the (two-magnon) saturation field (which is about 45 T), as well as an incommensurate collinear SDW phase at lower fields (which occupies a huge magnetization/field interval, extending down to about 7.5 T). In fact, the material seems to nicely realize the theoretical scenario outlined in Section II B 2: despite being in a one-dimensional spin-nematic state 35,36 , the chains order into a two-dimensional nematic phase only in the immediate vicinity of the saturation field 37 .…”

Anomalous fractional quantization in the kagomelike Heisenberg ladder: Emergence of the effective spin-1 chain

“…3(d), a commensurate peak of S ss (q) at q = π/2 has been obtained for J b /|J 1 | = 1. In fact, the propagation number is q = 0.4994π for [42]. Thus, the L = 72 PBC cluster used for Fig.…”