Defect-Mediated Pairing and Dissociation of Strongly Correlated Electrons in Low Dimensional Lattices: The Quantum Taxi Effect

TL;DR

This paper investigates how local site energy defects can induce pairing or dissociation of strongly correlated electrons in a one-dimensional lattice, revealing resonance-driven transitions between bound and dissociated states.

Contribution

It introduces a novel effective single-particle framework to analyze defect-induced pairing and dissociation in strongly correlated electron systems, highlighting resonance mechanisms.

Findings

Resonance between eigenstates enables pairing/dissociation transitions.

Transitions occur near the site energy defect when U, V, and Δ are comparable.

The effective two-dimensional network model explains the dynamics.

Abstract

We study the quantum dynamics of a strongly correlated electron pair in a one-dimensional lattice, focusing on the occurrence of local dissociation/pairing mechanisms induced by a site energy defect. To this end, we simulate the time evolution of two interacting electrons on a finite-size chain governed by an extended Hubbard Hamiltonian including on-site Coulomb repulsion $ U $ and nearest-neighbor interaction $V$, along with single-electron hopping $J$. By introducing a local site energy defect with amplitude $ \Delta $, we show that a transition between spatially paired/dissociated electrons can occur in the vicinity of this site. Such mechanisms arise in a strongly correlated regime with non-zero nearest neighbor Coulomb interactions and under the conditions $ (U \sim V \sim \Delta) \gg J$. To rationalize these phenomena, we reformulate the two-electron dynamics of the original Hubbard chain as an effective single-particle problem on a two-dimensional network. Within this framework, we show that the pairing/dissociation dynamics are driven by resonances between two distinct families of two-electron eigenstates: $(i)$ states with two spatially well-separated electrons with one located at the site defect, and $(ii)$ states with locally bound electron located away from the defect. At resonance, these states hybridize, allowing transitions from locally paired to dissociated electrons (and vice versa) in the vicinity of the defect. These results provide new insights into exotic pairing phenomena in strongly correlated electronic systems and may have implications for the design of tunable many-body states in low-dimensional quantum materials.