A variational Jastrow coupled-cluster theory of quantum many-body systems

TL;DR

This paper introduces a novel variational coupled-cluster method incorporating a Jastrow function to effectively capture many-body correlations in quantum systems of bosons and fermions, improving energy calculations.

Contribution

It combines coupled-cluster and Jastrow approaches, providing a new energy functional that avoids divergence issues in hardcore potentials and offers detailed formulas for practical evaluation.

Findings

Derived a first-order energy functional for the combined approach

Provided formulas for higher-order contributions to the energy functional

Achieved a divergence-free energy calculation for systems with hardcore potentials

Abstract

We study many-body correlations in the ground states of a general quantum system of bosons or fermions by including an additional Jastrow function in our ecently proposed variational coupled-cluster method. Our approach combines the dvantages of state-dependent correlations in the coupled-cluster theory and of strong, short-ranged correlations of the Jastrow function. We apply a generalized linked-cluster expansion for the Jastrow wavefunction and provide detailed analysis for practical evaluation of Hamiltonian expectation value as an energy functional of the Jastrow function and the bare density-distribution functions introduced and calculated in our earlier publications; a simple, first-order energy functional is derived and detailed formulas for higher-order contributions are provided. Our energy functional does not suffer the divergence as in most coupled-cluster calculations when applying to Hamiltonians with hardcore potentials. We also discuss relations between our energy functional and the energy functionals from other theories.