Deep in the electron-doped cuprate pseudogap regime: a two-particle self-consistent approach with <i>GG</i>₀ approximation to the two-dimensional Hubbard model

In cuprate high-T_c superconductors, the pseudogap (PG) manifests itself at low temperature as a gradual depletion of the density of states at the Fermi level. In electron-doped cuprates, the nonperturbative semianalytical two-particle-self-consistent (TPSC) approach naturally explains the PG as the finite-T precursor of the antiferromagnetic (AFM) bands of the ordered ground state at T=0. In contrast to Mott physics, the PG opens in two dimensions at hot spots in momentum space due to scattering off spin-fluctuations when the AFM correlation length becomes longer than the thermal de Broglie wavelength. However, TPSC eventually fails at temperatures deep in the PG regime with exponentially growing AFM correlation length. Here, we extend TPSC with the GG₀ approximation to the irreducible particle-hole polarization where one of the propagators G is self-consistently dressed by TPSC self-energy. Benchmarking with other controlled numerical methods, we demonstrate that this modified TPSC approach predicts quite accurate one-particle and two-particle properties deep in the PG regime, satisfies various sum rules and consistency relations and joins smoothly with the T=0 AFM ground state.