Variational theory combining number-projected BCS and coupled-cluster doubles

Abstract

The ground state pairing correlations in finite fermionic systems are described with a high degree of accuracy within a variational approach based on a combined coupled-cluster and particle-number-projected BCS ansatz. The flexibility of this symmetry-preserving wavefunction enables a unified picture valid from weak to strong coupling, both in small and large systems. The present variational approach consistently yields an energy upper bound while operating at the same level of precision of the non-variational particle-number projected Bogoliubov-coupled-cluster theory [Phys. Rev. C 99, 044301 (2019)].

10 pages, 5 figures

References in corpus (7)

• Quasiparticle Coupled Cluster Theory for Pairing Interactions
• Symmetry broken and restored coupled-cluster theory I. Rotational symmetry and angular momentum
• Accuracy of BCS-based approximations for pairing in small Fermi systems
• Exploring non-linear correlators on AGP
• Construction of linearly independent non-orthogonal AGP states
• Combining symmetry breaking and restoration with configuration interaction: a highly accurate many-body scheme applied to the pairing Hamiltonian
• A variational method for integrability-breaking Richardson-Gaudin models

Cited by in corpus (5)

• Density Matrices of Seniority-Zero Geminal Wavefunctions
• AGP-based unitary coupled cluster theory for quantum computers
• Robust formulation of Wick's theorem for computing matrix elements between Hartree-Fock-Bogoliubov wavefunctions
• Reduced basis emulation of pairing in finite systems
• Symmetry projection to coupled-cluster singles and doubles wave function through the Monte Carlo method