A mechanism for pair formation in strongly correlated systems

TL;DR

This paper introduces an exactly solvable model combining fermions and bosons with a Jaynes-Cummings interaction, revealing how electron pairing and energy gaps emerge from fundamental quantum principles in strongly correlated systems.

Contribution

It presents a novel exactly solvable model that demonstrates pair formation and energy gaps due to quantum interactions and the Pauli exclusion principle.

Findings

Electrons form bound pairs with opposite momentum and spin.

A gap appears in the fermion kinetic energy spectrum.

The model's gap is due to Pauli exclusion, not mean-field effects.

Abstract

We start from a Hamiltonian describing non-interacting fermions and add bosons to the model, with a Jaynes-Cummings-like interaction between the bosons and fermions. Because of the specific form of the interaction the model can be solved exactly. In the ground state, part of the electrons form bound pairs with opposite momentum and spin. The model also shows a gap in the kinetic energy of the fermions, but not in the spectrum of the full Hamiltonian. This gap is not of a mean-field nature, but is due to the Pauli exclusion principle.