Speaker
Description
Originating from Fermi liquid theory, the quasiparticle concept is the fundamental workhorse of solid-state physics. However, while it describes many-body systems in many materials, it fails to account for the exotic phases emerging from strong electronic correlations. We investigate the stability of the spin polaron quasiparticle by examining the 2D $t-J^z$ model and introducing a next-nearest-neighbor hopping $t'$, which results in the $t-t'-J^z$ model. Using an exact diagonalization approach based on ARPACK, we solved single-hole doped systems in the antiferromagnetic regime with a fixed Ising coupling of $J^z = 0.4t$ and varied $t'$ from $-0.5t$ to $0.5t$. We performed a finite-size scaling analysis of the quasiparticle weight at the $\Gamma$-point and $X$-point for lattices of up to 32 sites. Extrapolation toward the thermodynamic limit reveals an “anomalous” regime at the Γ-point for $t'\leq-0.3t$, characterized by a vanishing quasiparticle weight. To characterize the low-energy dynamics within this regime ($t'\leq-0.3t$), we evaluated the spin correlations centered around the hole and the magnon number distribution on a 20-site lattice. Based on these results, we propose a preliminary picture of the single-hole doped antiferromagnetic ground state within the “anomalous” regime. This state deviates from the well-known spin polaron because the cloud of magnetic fluctuations, typically localized around the hole, delocalizes over the whole finite-size lattice. Consequently, such systems show a weakly suppressed antiferromagnetic configuration under single-hole doping.