Hole pairing and ground state properties of high-Tc superconductivity within the t–t′–J–V model

The t – t ′ – J – V model, one of the realistic models for studying high- T c cuprates, has been investigated to explore the hole pairing and other ground state properties using exact diagonalization (ED) technique with 2 holes in a small 8-site cluster. The role of next-nearest-neighbor (NNN) hopping and nearest-neighbor (NN) Coulomb repulsion has been considered. It appears that qualitative behavior of the ground state energies of an 8-site and 16- or 18-site cluster is similar. Results show that a small short-ranged antiferromagnetic (AF) correlation exists in the 2 hole case which is favored by large V ∕ t . A superconducting phase emerges at 0 ≤ V ∕ t ≤ 4 J . Hole–hole correlation calculation also suggests that the two holes of the pair are either at | i − j | = 1 or √2. Negative t ′ ∕ t suppresses the possibility of pairing of holes. Though s -wave pairing susceptibility is dominant, pairing correlation length calculation indicates that the long range pairing, which is suitable for superconductivity, is in the d -wave channel. Both s - and d -wave pairing susceptibility gets suppressed by V ∕ t while d -( s -) wave susceptibility gets favored (suppressed) by t ′ ∕ t . The charge gap shows a gapped behavior while a spin-gapless region exists at small V ∕ t for finite t ′ ∕ t .