Self-localized domain walls at π-conjugated branching junctions

Area of Science:

• Condensed Matter Physics
• Materials Science
• Organic Electronics

Background:

• π-conjugated systems exhibit unique electronic properties due to delocalized electrons.
• Electron-phonon couplings play a crucial role in the formation and dynamics of self-localized excitations.
• Branching junctions in conjugated materials can create localized potential wells.

Purpose of the Study:

• To investigate the trapping of self-localized domain walls at π-conjugated branching junctions.
• To quantify the potential well depths for different types of domain walls (solitons, polarons, excitons).
• To explore the effect of junction filling and torsions on domain wall behavior and electronic properties.

Main Methods:

• Utilized an adapted Su-Schrieffer-Heeger model Hamiltonian to calculate potential well depths.
• Employed ab initio Hartree-Fock methods for comparative calculations.
• Analyzed the influence of torsions on junction band gap and electron localization.

Main Results:

• Self-localized domain walls (solitons, polarons, excitons) are found to be trapped at branching junction potential wells.
• Calculated potential well depths vary for different domain wall types and methods (e.g., 0.14 eV for soliton via SSH, 0.23 eV via HF).
• Branching junctions become repulsive to additional domain walls once their trapping wells are saturated; torsions significantly impact band gap and localization.

Conclusions:

• Intrinsic electron-phonon couplings enable the trapping of domain walls at π-conjugated branching junctions.
• The trapping capacity of junctions is finite, leading to repulsive behavior upon saturation.
• Torsional degrees of freedom at the junction are critical for tuning electronic properties and localization phenomena.