Bond Randomness Induced Magnon Decoherence in a Spin-1/2 Ladder Compound

Abstract

We have used a combination of neutron resonant spin-echo and triple-axis spectroscopies to determine the energy and linewidth of the magnon resonance in IPA-Cu(Cl${}_{0.95}$Br${}_{0.05}$)${}_3$, a model spin-1/2 ladder antiferromagnet where Br substitution induces bond randomness. We find that the bond defects induce a blueshift, $\delta \Delta$, and broadening, $\delta \Gamma$, of the magnon gap excitation compared to the pure compound. At temperatures exceeding the energy scale of the inter-ladder exchange interactions, $\delta \Delta$ and $\delta \Gamma$ are temperature independent within the experimental error, in agreement with Matthiessen's rule according to which magnon-defect scattering yields a temperature independent contribution to the magnon mean free path. Upon cooling, $\delta \Delta$ and $\delta \Gamma$ become temperature dependent and saturate at values lower than those observed at higher temperature, consistent with the crossover from one-dimensional to two-dimensional spin correlations with decreasing temperature previously observed in pure IPA-CuCl${}_3$. These results indicate limitations in the applicability of Matthiessen's rule for magnon scattering in low-dimensional magnets.

4 pages, 3 figures

References in corpus (4)

• Field-induced Tomonaga-Luttinger liquid phase of a two-leg spin-1/2 ladder with strong leg interactions
• Phase diagram of hard-core bosons on clean and disordered 2-leg ladders: Mott insulator - Luttinger liquid - Bose glass
• Mesoscopic Phase Coherence in a Quantum Spin Fluid
• Magnon Heat Conductivity and Mean Free Paths in Two-Leg Spin Ladders: A Model-Independent Determination

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