NMR relaxation in the spin-1 Heisenberg chain
Résumé
We consider the isotropic S = 1 Heisenberg chain with a finite Haldane gap ∆ and use state-of-the-art numerical techniques to investigate its dynamical properties at finite temperature, focusing on the nuclear spin-lattice relaxation rate 1/T1 measured in nuclear magnetic resonance (NMR) experiments for instance. In particular, we analyze the contributions from modes with momenta close to q ≈ 0 and q ≈ π as a function of temperature. At high-temperature we observe spin diffusion, while at low-temperature we argue that a simple activated behavior 1/T1 ∝ exp(−∆/T) can be observed only at temperatures much smaller than the gap ∆.
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