Low-lying quasiparticle excitations in strongly correlated superconductors: An ansatz from BCS quasiparticle excitations?

• A method is developed to examine two-particle Gutzwiller-projected BCS excitations.
• GBQP is an appropriate low-lying picture in strongly correlated superconductors.
• We find intimate relation between Gutzwiller's projection and d-wave Cooper pairing.

The question about the existence of Bogoliubov's quasiparticles in the BCS wave functions underneath Gutzwiller's projection is of importance to strongly correlated systems. We develop a method to examine the two-particle excitations of Gutzwiller-projected BCS wave functions by using the variational Monte Carlo approach. We find that the exact Gutzwiller-projected quasiparticle (GQP) dispersions are quantitatively reproduced by the Gutzwiller-projected Bogoliubov quasiparticles (GBQP) except the regions where d-wave Cooper pairing is strong. We believe GBQP provides a reasonable description to the low-energy excitations in strongly correlated superconducting systems because GBQP becomes more stable than GQP near the antinodes. Our framework offers a route to understand the intimate connection between Gutzwiller's projection and d-wave Cooper pairing.