Effect of disorder on the relaxation of photoexcited states in one‐dimensional Mott insulators

Abstract

AbstractWe theoretically investigate the effect of static disorder on the dynamics of photoexcited states in onedimensional Mott insulators. We adopt the Pariser‐Parr‐Pople model, where disorder is introduced in the site energy and the transfer integral. We numerically calculate the time development of the state excited by a light pulse, and investigate the time dependence of the nearest‐neighbor spin‐spin interaction energy, the on‐site Coulomb interaction energy, and the kinetic energy of photogenerated charges. In the weaker excitation case, the energy transfer from the charge degrees of freedom to the spin degrees of freedom does not occur in the regular systems as a result of the spin‐charge separation. When the disorder in the transfer integral is introduced, the spin‐spin interaction energy changes with time after photoexcitation, showing that the spin‐charge coupling is induced in this case.The effects of the disorder in the site energy on the spincharge coupling are much weaker than those in the transfer integral. On the contrary, the energy transfer from the on‐site Coulomb interaction energy to the kinetic energy is strongly suppressed by these two kinds of disorders. In the stronger excitation case, the spin and the charge degrees of freedom are coupled in the photoexcited states, and the two kinds of energy transfers occur even in regular systems. Furthermore, these energy transfers occur in irreversible way, suggesting that these transfers are relaxation phenomena. These relaxations are enhanced by the disorders. There are no significant differences in the effects of disorders on these relaxations between the disorder in the site energy and that in the transfer integral. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)