Collective mode spectra and dynamical response functions of weakly coupled random spin chains

We study the dynamics of weakly coupled random antiferromagnetic spin chains at low temperature. We use the celebrated real-space renormalization group technique to tackle the intrachain couplings, and treat the interchain couplings within the Mean-Field/Random Phase Approximation (RPA) framework. Earlier work based on mean-field treatment of the inter chain couplings[joshi] indicated the existence of disorder-induced Neel ordering in such systems and clarified their phase diagrams. In the present work we apply the RPA formalism to calculate the dynamical response functions in the low temperature ordered phase. We obtain the dynamical susceptibility, structure factor, and the spin-wave spectra. Comparisons will be made with inelastic neutron scattering experiment for quasi-one-dimensional spin systems such as CuGeO$_3$. \\ \\ \textbf{References} \newline [joshi] Anuvrat Joshi and Kun Yang, Phys. Rev. B \textbf{67}, 174403 (2003)