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 (1p_1/2, 0g_9/2) proton and (1d_5/2, 2s_1/2, 1d_3/2, 0g_7/2, 0h_11/2) 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.