Charge density plateaux and insulating phases in the <InlineEquation ID="Equ1"> <EquationSource Format="TEX">$\mathsf{t-J}$</EquationSource> </InlineEquation> model with ladder geometry

We discuss the occurrence and the stability of charge density plateaux in ladder-like t-J systems (at zero magnetization M=0) for the cases of 2- and 3-leg ladders. Starting from isolated rungs at zero leg coupling, we study the behaviour of plateaux-related phase transitions by means of first order perturbation theory and compare our results with Lanczos diagonalizations for t-J ladders (N=2 × 8) with increasing leg couplings. Furthermore we discuss the regimes of rung and leg couplings that should be favoured for the appearance of the charge density plateaux. Copyright Springer-Verlag Berlin/Heidelberg 2003