Polaronic effects in strongly coupled electron-phonon systems: Exact diagonalization results for the 2D Holstein t-J model

TL;DR

This paper investigates the ground-state and dynamical properties of the 2D Holstein t-J model, revealing polaron formation, bipolaronic states, and superlattice structures through exact diagonalization techniques.

Contribution

It provides the first detailed analysis of polaronic effects in the 2D Holstein t-J model using Lanczos diagonalization with phononic Hilbert space truncation.

Findings

Formation of a narrow hole-polaron band with increased electron-phonon coupling

Existence of inter-site bipolaronic states in the two-hole sector

Polaronic superlattice formation at quarter-filling in strong-coupling regime

Abstract

Ground-state and dynamical properties of the 2D Holstein t-J model are examined by means of direct Lanczos diagonalization, using a truncation method of the phononic Hilbert space. The single-hole spectral function shows the formation of a narrow hole-polaron band as the electron-phonon coupling increases, where the polaronic band collapse is favoured by strong Coulomb correlations. In the two-hole sector, the hole-hole correlations unambiguously indicate the existence of inter-site bipolaronic states. At quarter-filling, a polaronic superlattice is formed in the adiabatic strong-coupling regime.