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

TL;DR

This paper develops a variational Monte Carlo method to analyze quasiparticle excitations in Gutzwiller-projected BCS wave functions, revealing that Gutzwiller-projected Bogoliubov quasiparticles effectively describe low-energy excitations in strongly correlated superconductors.

Contribution

The study introduces a new approach to compare Gutzwiller-projected quasiparticles with Bogoliubov quasiparticles, highlighting their similarities and differences in strongly correlated systems.

Findings

Gutzwiller-projected Bogoliubov quasiparticles closely match Gutzwiller-projected quasiparticle dispersions.

Discrepancies occur near antinodes where d-wave pairing is strong.

GBQP provides a reasonable low-energy excitation description in strongly correlated superconductors.

Abstract

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.