Using the Density Matrix Renormalization Group method, we determined the phase diagram of a frustrated antiferromagnetic spin-
21 ladder at zero temperature. Two spin-gapped phases, the Haldane phase and the singlet phase, are identified. A phase transition between the two phases occurs at any non-zero value of frustration coupling
J×. On the phase boundary, the spin gap vanishes for sufficiently small
J×. Crossing this non-gapped line, the transition is of second order, while of first order for larger
J×. Striking frustration effects are predicted for ladder materials.
Using the density matrix renormalization group method, we determined the phase diagram of a frustrated antiferromagnetic spin-[Formula: see text] ladder at zero temperature. Two spin-gapped phases, the Haldane phase and the singlet phase, are identified. In particular, impurity effects are experimentally detectable for the Haldane phase. A phase transition between the two phases occurs at any nonzero value of frustration coupling J×. On the phase boundary, the spin gap vanishes for sufficiently small J×. Crossing this line of gapless states, the transition is of second order, while it is of first order for larger J×.