Polaron superlattices in n-doped single conjugated polymers.

The presence of multiple polarons, particularly at high doping levels, involves complex many-body interactions that substantially influence the electronic and transport properties of various materials. Determining the spatial distributions of coupled electronic and vibrational states is essential to understanding interacting polarons at a microscopic level but remains a challenge. Here we report the crystallization of electron polarons into quasi-one-dimensional polaron superlattices in highly n-doped single ethynylene-bonded polypentacenes. We employ integrated scanning tunnelling microscopy, atomic force microscopy and tip-enhanced Raman spectroscopy combined with first-principles density functional theory to correlate electronic, vibrational and structural information. The observed polaron superlattices exhibit different periodicities that depend on the doping levels. Their real-space polaron wavefunctions are determined by the intertwined electronic and vibrational periodic modulations associated with the periodic lattice distortions as resolved by atomic force microscopy. We can then identify the multiband charge-density-wave attributes of interacting polarons in these superlattices. Our findings provide microscopic insights in interacting polarons, which is important for the understanding of polaronic charge transport mechanisms in organic semiconductors.