Evidence for the formation of a Mott state in potassium-intercalated pentacene

TL;DR

This study demonstrates that potassium-intercalated pentacene exhibits a Mott metal-insulator transition driven by electron-electron interactions, with metallic behavior at certain concentrations and insulating behavior at higher levels.

Contribution

It provides experimental evidence and theoretical analysis of a Mott transition in potassium-intercalated pentacene, a phenomenon not previously observed in this material.

Findings

Potassium-intercalated pentacene shows metallic behavior at specific doping levels.

Increasing potassium concentration beyond one atom per molecule induces an insulating state.

The transition is attributed to a Mott metal-insulator transition caused by electron-electron interactions.

Abstract

We investigate electronic transport through pentacene thin-films intercalated with potassium. From temperature-dependent conductivity measurements we find that potassium-intercalated pentacene shows metallic behavior in a broad range of potassium concentrations. Surprisingly, the conductivity exhibits a re-entrance into an insulating state when the potassium concentration is increased past one atom per molecule. We analyze our observations theoretically by means of electronic structure calculations, and we conclude that the phenomenon originates from a Mott metal-insulator transition, driven by electron-electron interactions.