Impurity-induced pairing in two-dimensional Fermi gases

TL;DR

This paper investigates impurity-induced pairing in two-dimensional Fermi gases, revealing how confinement and interaction range enhance trimer stability and suggesting new pathways for electron pairing beyond traditional superconductivity.

Contribution

It introduces a stochastic variational approach to analyze impurity-mediated pairing, highlighting effects of confinement and finite interaction range on three-body states in 2D systems.

Findings

Confinement and finite interaction range significantly stabilize trimers.

Exciton-mediated interactions can surpass Coulomb repulsion in semiconductors.

Potential for realizing novel electron pairing mechanisms.

Abstract

We study induced pairing between two identical fermions mediated by an attractively interacting quantum impurity in two-dimensional systems. Based on a Stochastic Variational Method (SVM), we investigate the influence of confinement and finite interaction range effects on the mass ratio beyond which the ground state of the quantum three-body problem undergoes a transition from a composite bosonic trimer to an unbound dimer-fermion state. We find that confinement as well as a finite interaction range can greatly enhance trimer stability, bringing it within reach of experimental implementations such as found in ultracold atom systems. In the context of solid-state physics, our solution of the confined three-body problem shows that exciton-mediated interactions can become so dominant that they can even overcome detrimental Coulomb repulsion between electrons in atomically-thin semiconductors. Our work thus paves the way towards a universal understanding of boson-induced pairing across various fermionic systems at finite density, and opens perspectives towards realizing novel forms of electron pairing beyond the conventional paradigm of Cooper pair formation.