Polaron Excitations in Doped C60: Effects of Disorders

TL;DR

This study investigates how various types of disorder affect polaron excitations and lattice distortions in doped C60, revealing their stability in light doping and breakdown in heavy doping scenarios.

Contribution

It introduces a detailed simulation of disorder effects on polaron and dimerization stability in doped C60 using a Su-Schrieffer-Heeger--type model.

Findings

Polaron and dimerization stability in lightly doped C60.

Disorder causes merging of peaks, indicating breakdown of polaron structures.

Heavy doping reduces dimerization strength and polaron stability.

Abstract

Effects on C$_{60}$ by thermal fluctuations of phonons, misalignment of C$_{60}$ molecules in a crystal, and other intercalated impurities (remaining C$_{70}$, oxygens, and so on) are simulated by disorder potentials. The Su-Schrieffer-Heeger--type electron-phonon model for doped C$_{60}$ is solved with gaussian bond disorders and also with site disorders. Sample average is performed over sufficient number of disorder configurations. The distributions of bond lengths and electron densities are shown as functions of the disorder strength and the additional electron number. Stability of polaron excitations as well as dimerization patterns is studied. Polarons and dimerizations in lightly doped cases (C$_{60}^{-1,-2}$) are relatively stable against disorders, indicated by peak structures in distribution functions. In more heavily doped cases, the several peaks merge into a single peak, showing the breakdown of polaron structures as well as the decrease of the dimerization strength. Possibility of the observation of polaronic lattice distortions and electron structures in doped C$_{60}$ is discussed.