  The phase diagram of the two-leg t-Jz ladder is explored, using the density
matrix renormalization group method. Results are obtained for energy gaps,
electron density profiles and correlation functions for the half-filled and
quarter-filled cases. The effective Lagrangian velocity parameter is shown to
vanish at half-filling. The behaviour of the one-hole gap in the Nagaoka limit
is investigated, and found to disagree with theoretical predictions. A
tentative phase diagram is presented, which is quite similar to the full t-J
ladder, but scaled up by a factor of about two in coupling. Near half-filling a
Luther-Emery phase is found, which may be expected to show superconducting
correlations, while near quarter-filling the system appears to be in a
Tomonaga-Luttinger phase.
