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

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. Since GQP still shows higher energy than GBQP near the antinodes, we believe GBQP provides a reasonable description to the low-energy excitations in strongly correlated superconducting systems. In addition, the intimate connection between Gutzwiller's projection and d-wave Cooper pairing may also imply that strong correlations play a significant role in the nodal-antinodal dichotomy seen by photoemission experiments in cuprates.