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Identification of Nuclear Relaxation Processes in a Gapped Quantum Magnet: Proton NMR in the S=1/2 Heisenberg Ladder Cu2(C5H12N2)2Cl4

G. Chaboussant·M. -H. Julien·Y. Fagot-Revurat·L. P. Levy·C. Berthier·M. Horvatic·O. Piovesana
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Abstract

The proton hyperfine shift K and NMR relaxation rate $1/T_1$ have been measured as a function of temperature in the S=1/2 Heisenberg antiferromagnetic ladder Cu2(C5H12N2)2Cl4. The presence of a spin gap $Δ\simeq J_\perp-J_\parallel$ in this strongly coupled ladder ($J_\parallel < J_\perp$) is supported by the K and $1/T_1$ results. By comparing $1/T_1$ at two different proton sites, we infer the evolution of the spectral functions $S_z(q,ω_n)$ and $S_\perp(q,ω_n)$. When the gap is significantly reduced by the magnetic field, two different channels of nuclear relaxation, specific to gapped antiferromagnets, are identified and are in agreement with theoretical predictions.

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G. Chaboussant, M. -H. Julien, Y. Fagot-Revurat, L. P. Levy, C. Berthier, M. Horvatic, O. Piovesana. 1997-06-13. Identification of Nuclear Relaxation Processes in a Gapped Quantum Magnet: Proton NMR in the S=1/2 Heisenberg Ladder Cu2(C5H12N2)2Cl4. https://doi.org/10.1103/physrevlett.79.925

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