Bipolaron

About: Bipolaron is a research topic. Over the lifetime, 1335 publications have been published within this topic receiving 29154 citations. The topic is also known as: bipolarons.

Interacting Bipolarons in n-Doped Sexiphenyl Films

Abstract: The formation and evolution of the gap states formed with increasing Cs concentration in thin sexiphenyl (6P) films is followed with ultraviolet photoemission spectroscopy (UPS). Two distinct doping regimes are apparent, experimental considerations suggest that in the lower-doping bipolaron-like (dianionic 6P2-) states are formed. In the higher-doping regime, approaching Cs saturation, a 0.4 eV splitting in the gap states is observed which is attributed to interacting bipolaron states. VEH calculations for 6P2- and 6P4- are in very good agreement with the experimental spectra and lend strong support to the notion that a bipolaron to intrachain interacting bipolaron transition occurs with increasing Cs concentration.

Organic single-crystal surface-induced polymerization of conducting polypyrroles.

Abstract: Polypyrrole hexagonal microplates (PHMs) (50-100 microm long, 10-20 microm wide, and 0.8-1.2 microm thick) with a quasicrystalline structure and high electrical conductivity (up to 400 S/cm) are simply fabricated using single crystals of 4-sulfobenzoic acid monopotassium salt (KSBA) in aqueous medium. Moreover, the fabrication process described here differs strikingly from traditional methods, such as template-free, soft template, and hard template methods. Synthetic time-resolved polypyrrole (PPy) morphology dynamics reveals that the fabrication process of PHMs composed of PPy nanostructures combines a shape-copying process for forming a PPy preform that imitates the shape of a KSBA single crystal and the self-assembly process of PPys on the preform. The PHMs exhibit the improved pi-stacking and bipolaron structure. The strong pi-stacks among PPy rings of bipolaron structures lead to a high quasicrystalline structural order and the metallic conduction. Other single organic crystals that can act as dopants could also be grown using this approach, which will also enable the fabrication of complex micro/nanostructures on organic single crystals.

The "crab" bipolaron as a possible route to room temperature superconductivity

Abstract: We study a lattice bipolaron on a staggered triangular ladder and triangular and hexagonal lattices with both long-range electron-phonon interaction and strong Coulomb repulsion using a novel continuous-time quantum Monte-Carlo (CTQMC) algorithm extended to the Coulomb-Frohlich model with two particles. The algorithm is preceded by an exact integration over phonon degrees of freedom, and as such is extremely efficient. The bipolaron effective mass and bipolaron radius are computed. Lattice bipolarons on such lattices have a novel crablike motion, and are small but very light in a wide range of parameters, which leads to a high Bose-Einstein condensation temperature. We discuss the relevance of our results with current experiments on cuprate high-temperature superconductors and propose a route to room temperature superconductivity.

Electronic structure of highly conducting conjugated polymers: evolution upon doping of polyacetylene, polythiophene, and polyemeraldine

Abstract: The electronic properties of three types of conducting polymers: trans -polyacetylene (proto-typical of systems with a degenerate ground state), polythiophene (as an example of compounds with a nondegenerate ground state), and polyemeraldine (which can be doped via protonation) are reviewed. The structural and electronic band structure properties of these systems are studied at various defect concentrations corresponding to undoped, lightly doped, and highly doped polymers. Geometry optimizations of oligomeric equivalents to the undoped and doped polymers are performed using the semi-empirical MNDO and AM1 methods. The electronic band structures are calculated using the VEH method. The interpretation of the optical absorption data is discussed in terms of interband transitions; for doped trans -polyacetylene including soliton defects and for doped polythiophene including bipolaron defects. For highly doped trans -polyacetylene and polythiophene as well as for protonated polyemeraldine, the electronic structure of a polaron lattice conformation is discussed and shown to be in agreement with existing optical and magnetic data on these polymers.