Abstract
Modern theories of quantum magnetism predict exotic multipolar states in weakly interacting strongly frustrated spin-1/2 Heisenberg chains with ferromagnetic nearest neighbor (NN) inchain exchange in high magnetic fields. Experimentally these states remained elusive so far. Here we report strong indications of a magnetic field-induced nematic liquid arising above a field of ~13 T in the edge-sharing chain cuprate LiSbCuO4 ≡ LiCuSbO4. This interpretation is based on the observation of a field induced spin-gap in the measurements of the 7Li NMR spin relaxation rate T1−1 as well as a contrasting field-dependent power-law behavior of T1−1 vs. T and is further supported by static magnetization and ESR data. An underlying theoretical microscopic approach favoring a nematic scenario is based essentially on the NN XYZ exchange anisotropy within a model for frustrated spin-1/2 chains and is investigated by the DMRG technique. The employed exchange parameters are justified qualitatively by electronic structure calculations for LiCuSbO4.
Highlights
We have presented strong experimental and theoretical indications of the occurrence of a distinctive spin-nematic state in the frustrated anisotropic spin chain cuprate LiCuSbO4
To model the Li split positions Li1a (4a), Li1b (4a) and Li2 (8b), we used averaged coordinates: Li1 (4a) 0.0 0.3610 0.6974 or the coordinates of the nearby high symmetry position Li2 (4a) 0. 0.0002 0.2660; Li split positions have been successfully modeled this way for the related edge-sharing chain compound LiZrCuO461
Summary
The central experimental result of this work is an observation of distinct temperature and magnetic field dependences of the 7Li NMR relaxation rate T1−1 in the short-range ordered (SRO) state of LiCuSbO4 below ~10 K, as shown, which will be discussed in the following. In weakly coupled unfrustrated critical simple AFM Heisenberg chains in the paramagnetic state far above the Neél ordering temperature TN T J/kB, the rateT1−1 in general continuously increases with decreasing T and/or increasing the magnetic field H up to the saturation field and tends to diverge by approaching TN This is mainly due to the growth of the Sj+(t)S0−(0) correlation function with increasing H and decreasing T whereas Sjz(t)S0z(0) decays smoothly following a power law[35,36,37]. At 9 T, Tc is pushed up to ~1.5 K indicating the proximity to a new, field-induced magnetic state that has been revealed in the specific heat data in ref
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