Shell model Monte Carlo method in the pn-formalism

We report on the development of a new shell-model Monte Carlo algorithm, which uses the proton-neutron formalism. Shell model Monte Carlo methods, within the isospin formulation, have been successfully used in large-scale shell-model calculations. Motivation for this work is to extend the feasibility of these methods to shell-model studies involving non-identical proton and neutron valence spaces. We show the viability of the new approach with some test results. Finally, we use a realistic effective nucleon-nucleon interaction in the model space described by (1p1/2 , 0g9/2) proton and (1d 5/2, 2s1/2, 1d3/2 , 0g7/2, 0h11/2) neutron orbitals above the 88Sr core to calculate ground-state energies, binding energies, B(E2) strengths, and study pairing properties of the even-even 90--104Zr and 92--106Mo isotope chains.