Abstract
We report a novel crossover behavior in the long-range-ordered phase of a prototypical spin-1/2 Heisenberg antiferromagnetic ladder compound (C_{7}H_{10}N)_{2}CuBr_{4}. The staggered order was previously evidenced from a continuous and symmetric splitting of ^{14}N NMR spectral lines on lowering the temperature below T_{c}≃330 mK, with a saturation towards ≃150 mK. Unexpectedly, the split lines begin to further separate away below T^{*}∼100 mK, while the linewidth and the line shape remain completely invariable. This crossover behavior is further corroborated by the NMR relaxation rate T_{1}^{-1} measurements. A very strong suppression reflecting the ordering, T_{1}^{-1}∼T^{5.5}, observed above T^{*}, is replaced by T_{1}^{-1}∼T below T^{*}. These original NMR features are indicative of the unconventional nature of the crossover, which may arise from a unique arrangement of the ladders into a spatially anisotropic and frustrated coupling network.
Highlights
We report a novel crossover behavior in the long-range-ordered phase of a prototypical spin1/2 Heisenberg antiferromagnetic ladder compound (C7H10N)2CuBr4
Spin ladders in a magnetic field are a paradigmatic model in quantum magnetism and many-body physics [1, 2]
When the ladders are embedded in real material, a weak residual coupling between them comes into play at sufficiently low temperatures, and this dimensional crossover manifests itself as a secondorder phase transition into a canted XY ordered phase [1]. This 3D long-range-ordered (LRO) phase is described as a Bose-Einstein condensate (BEC) of magnons [1, 2, 5,6,7]
Summary
Minki; Mayaffre, H.; Berthier, C.; Schmidiger, D.; Zheludev, A.; Horvati, M. Document Version Peer reviewed version Citation for published version (Harvard): Jeong, M, Mayaffre, H, Berthier, C, Schmidiger, D, Zheludev, A & Horvati, M 2017, 'Magnetic-order crossover in coupled spin ladders', Physical Review Letters, vol 118, no.
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