Polaronic Electron Transport in a Naphthalene Crystal from First Principles

Charge transport is notoriously difficult to predict in organic molecular crystals due to their complex electron-phonon (e-ph) interactions. Two limit transport regimes in organic crystals are bandlike transport dominated by intermolecular phonons [1] and polaron hopping governed by intramolecular phonons. However, an intermediate regime is also possible in which both the bandlike and hopping descriptions break down; an accurate method to predict transport in the intermediate regime is still missing. In this talk, we show that electron transport in a naphthalene crystal in the in-plane molecular directions belongs to the intermediate transport regime. We employ our recently developed finite-temperature cumulant approach [2] to accurately predict the in-plane electron mobility, obtaining results in excellent agreement with experiments between 100-300 K temperatures. Our results demonstrate that the intermediate electron transport regime in organic crystals parallels the large polaron picture in oxides. Analysis of the computed electron spectral functions reveals an interplay between intermolecular and intramolecular phonons.

[1] N.-E. Lee et al., Phys. Rev. B, 97, 115203 (2018)
[2] J.-J. Zhou et al., Phys. Rev. Research, 1, 033138 (2019)