Pair tunneling through single molecules

TL;DR

This paper investigates how pair tunneling dominates charge transport in molecules with negative charging energy, revealing unique current-voltage behaviors and potential for gate-controlled rectification.

Contribution

It demonstrates that pair tunneling can dominate in molecules with negative charging energy, leading to distinctive transport properties and applications in molecular electronics.

Findings

Charge transport is dominated by pair tunneling near ground-state degeneracies.

Current-voltage characteristics differ markedly from conventional Coulomb blockade.

Pair tunneling enables gate-controlled rectification and switching in asymmetric junctions.

Abstract

By a polaronic energy shift, the effective charging energy of molecules can become negative, favoring ground states with even numbers of electrons. Here, we show that charge transport through such molecules near ground-state degeneracies is dominated by tunneling of electron pairs which coexists with (featureless) single-electron cotunneling. Due to the restricted phase space for pair tunneling, the current-voltage characteristics exhibits striking differences from the conventional Coulomb blockade. In asymmetric junctions, pair tunneling can be used for gate-controlled current rectification and switching.