Vibrational spectrum and electron-phonon coupling of doped solid picene from first principles

TL;DR

This study uses first-principles calculations to analyze the phonon spectrum and electron-phonon interactions in doped solid picene, explaining its superconductivity and predicting effects of hole doping.

Contribution

It provides a detailed first-principles analysis of electron-phonon coupling in doped picene, linking phonon modes to superconducting transition temperatures.

Findings

Electron-phonon coupling explains Tc of 18 K in electron-doped picene.

Hole doping predicts a maximum Tc of 6 K.

Picene may be a strongly correlated electron-phonon superconductor similar to fullerides.

Abstract

We study superconductivity in doped solid picene (C22H14) with linear response calculations of the phonon spectrum and electron-phonon (ep) interaction. We show that the coupling of the high-energy C bond-stretching phonons to the {\pi} molecular orbitals for a doping of ~3 electrons per picene molecule is sufficiently strong to reproduce the experimental Tc of 18 K within Migdal-Eliashberg theory. For hole doping, we predict a similar coupling leading to a maximum Tc of 6 K. However, we argue that, due to its molecular nature, picene may belong to the same class of strongly correlated ep superconductors as fullerides. We propose several experimental tests for this hypothesis and suggest that intercalated hydrocarbons with different arrangements and numbers of benzene rings may be used to study the interplay between ep interaction and strong electronic correlations in the highly nonadiabatic limit.