Topic
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.
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TL;DR: In this article, the authors investigated the electronic excitation in aniline tetramers at various levels of oxidation and protonation and showed that for certain geometrical conformations there is excellent agreement between their results and recently published experimental data.
Abstract: We investigate the electronic excitation in aniline tetramers at various levels of oxidation and protonation. We show that for certain geometrical conformations there is excellent agreement between our results and recently published experimental data. The neutral forms of the tetramer are shown to have excitation spectra almost identical to polymer equivalents. For the doubly protonated emeraldine tetramer we propose a bipolaron type of defect state, unlike in its polymer equivalent for which a polaronic metal model has been proposed. The electronic transitions associated with the bipolaron are shown to involve only one bipolaron level in contrast to the common picture of two bipolaron levels.
42 citations
TL;DR: Investigation of transitions between bipolaron and polaron states in doped heterocycle polymers such as polypyrrole, polythiophene, and polyselenophene finds that the interchain coupling has little influence on the stability of a bipolaron.
Abstract: On the basis of a model similar to that of Su, Schrieffer, and Heeger, we investigate transitions between bipolaron and polaron states in doped heterocycle polymers such as polypyrrole, polythiophene, and polyselenophene. The dopant impurity is assumed to be located between chains, and the interchain coupling is due to the electron hopping which is assumed to be confined to nearest-neighboring carbon groups around the counterion. The electron-electron interaction described by a Hubbard-type Hamiltonian is also included in our calculation. It is shown that the system may be in a bipolaron state or a state of a polaron pair of spin triplet (singlet) nature. We find that the interchain coupling has little influence on the stability of a bipolaron. Transitions from a bipolaron to a pair of polarons can be induced by a strong electron-electron interaction, which is also responsible for the energy difference between the singlet and triplet polarons states.
41 citations
TL;DR: In this paper, the optical, electrical and dielectric properties of HCl doped polyaniline nanorods synthesized by the interfacial polymerization technique were investigated, and the existence of both polaron and bipolaron in the transport mechanism has been confirmed from the binding energy calculations.
Abstract: In this report we have investigated the optical, electrical and dielectric properties of HCl doped polyaniline nanorods synthesized by the interfacial polymerization technique. High resolution transmission electron microscope (HRTEM) micrographs confirm the formation of nanorods. X-ray diffraction pattern shows the semicrystalline nature of polyaniline nanorods with a diameter distribution in the range of 10–22 nm. The chemical and electronic structures of the polyaniline nanorods are investigated by micro-Raman and UV–vis spectroscopy. Dielectric relaxation spectroscopy has been applied to study the dielectric permittivity, modulus formalism and ac conductivity as a function of frequency and temperature. The ac conductivity follows a power law with frequency. The variation of frequency exponent with temperature suggests that the correlated barrier hopping is the dominant charge transport mechanism. The existence of both polaron and bipolaron in the transport mechanism has been confirmed from the binding energy calculations.
41 citations
TL;DR: In this article, the spin and charge texture around doped holes in the two-dimensional Hubbard model is calculated within an unrestricted spin rotational invariant slave-boson approach, and the most stable configuration corresponds to a vortex-antivortex pair which has lower energy than the Neel-type bipolaron even when taking the far field contribution into account.
Abstract: The spin and charge texture around doped holes in the two-dimensional Hubbard model is calculated within an unrestricted spin rotational invariant slave-boson approach. In the first part we examine in detail the spin structure around two holes doped in the half-filled system where we have studied cluster sizes up to 10 x 10. It turns out that the most stable configuration corresponds to a vortex-antivortex pair which has lower energy than the Neel-type bipolaron even when one takes the far field contribution into account. We also obtain skyrmions as local minima of the energy functional but with higher total energy than the vortex solutions. Additionally we have investigated the stability of elliptical domain walls for commensurate hole concentrations. We find that (i) these phases correspond to local minima of the energy functional only in case of partially filled walls, (ii) elliptical domain walls are only stable in the low doping regime.
41 citations
TL;DR: In this paper, in situ ESR-electrochemical experiments in conducting polymers are presented, where spin concentration has been measured as a function of doping level, and quantitative data are presented for the case of polypyrrole.
41 citations