We investigate the quantum phase diagram of the exactly solved mixed spin-(1 2 , 1) ladder via the thermodynamic Bethe ansatz (TBA). In the absence of a magnetic field the model exhibits three quantum phases associated with su(2), su(4) and su(6) symmetries. In the presence of a strong magnetic field, there is a third and full saturation magnetization plateaux within the strong antiferromagneti...

The Heisenberg model on a two-chain spin1 2 ladder with frustrating second-neighbor interactions is studied by using series expansions about the Ising and dimer limits, numerical diagonalization, and by Abelian bosonization analysis. The phase diagram is determined, and pair correlations and the complete dispersion relations for the triplet spin-wave excitations are also computed. @S0163-1829~9...

We present here a formulation for the calculation of the configuration averaged optical conductivity in random alloys. Our formulation is based on the Augmented Space Theorem introduced by one of us (Mookerjee,1973). We show that disorder scattering renormalizes the electron and hole propagators as well as the transition amplitude. We also study the effect of vertex corrections in a simplified ...