Effects of next-nearest-neighbor interactions on the dynamics of random quantum Ising model

Abstract

The dynamics of one-dimensional random quantum Ising model with both nearest-neighbor and next-nearest-neighbor （NNN） interactions is investigated in the high temperature limit by the method of recurrence relations. Spin autocorrelations and the corresponding spectral densities of the system are calculated. Supposing that the exchange couplings （or the transverse fields） satisfy the double-Gaussian distribution, the effects of this distribution on the dynamics of the system is studied. The results show that the dynamics of the system undergoes a crossover from a collective-mode behavior to a central-peak one when the standard deviations σJ（or σB）of the random variables are small and there is no crossover when σJ（or σB）are large. Meanwhile, the effects of NNN interactions on the dynamics of the system are studied. It is found that the central-peak behavior becomes more obvious and the collective-mode behavior becomes weaker as Ki increase, especially when Ki>Ji/2（Ji and Ki are exchange couplings of the NN and NNN interactions, respectively）. However, the effects are small when the NNN interactions are weak （KiJi/2）.