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.

Large-bipolaron transport and cuprate superconductors.

Abstract: The in-plane electronic transport of large bipolarons that move within parallel conducting sheets is considered The Coulomb interactions between the heavy bipolarons in this planar system produce a distinctive spectrum for collective excitations Transport of the quasiparticles associated with the collective excitations is treated via the conventional Boltzmann transport theory However, the scattering of the heavy quasiparticles by acoustic phonons is taken to be analogous to the distinctive scattering of individual large polarons In particular, as with strong-coupling (adiabatic) large polarons, the scattering time is taken to be proportional to the quasiparticle effective mass The resistivity, the Hall effect, and the thermoelectric power are determined with this scheme With a constant density of carriers, the resistivity is proportional to the temperature The Hall number, the number of carriers deduced from the reciprocal of the Hall constant, exceeds the true carrier density by a ratio that rises linearly with temperature In addition, the thermoelectric power falls in magnitude and ultimately changes sign as the temperature is raised These unusual transport properties, as well as the ir conductivity, are consistent with the observed behaviors of the high-${\mathit{T}}_{\mathit{c}}$ cuprate superconductors

Effect of oxidant on electronic transport in polypyrrole nanotubes synthesized in the presence of methyl orange

Abstract: Polypyrrole nanotubes with diameter 60–400 nm are synthesized with methyl orange as template and various oxidants, iron(III) chloride hexahydrate, iron(III) sulfate hydrate, and ammonium peroxydisulfate. The highest electrical conductivity of compressed pellets, 66 S cm−1, is found for iron(III) chloride. Regions with 3D variable range hopping in series with ordered regions near metal–insulator transition govern the charge transport. Other oxidants and globular morphology provide less conducting samples, <10 S cm−1. The transport mechanism is identified with the heterogeneous model of tunneling between (bi)polaronic clusters with parallel contribution of Arrhenius-like activated conductivity. The results of conductivity are correlated with the protonation level reflected in the infrared spectra and with the ratio of bipolaron/polaron bands revealed by Raman spectroscopy. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1147–1159

Light bipolarons stabilized by Peierls electron-phonon coupling

Abstract: It is widely accepted that phonon-mediated high-temperature superconductivity is impossible at ambient pressure, because of the very large effective masses of polarons or bipolarons at strong electron-phonon coupling. Here we challenge this belief by showing that strongly bound yet very light bipolarons appear for strong Peierls coupling. These bipolarons also exhibit many other unconventional properties; e.g., at strong coupling there are two low-energy bipolaron bands that are stable against strong Coulomb repulsion. Using numerical simulations and analytical arguments, we show that these properties result from the specific form of the phonon-mediated interaction, which is of "pair hopping" instead of regular density-density type. This unusual effective interaction is bound to have nontrivial consequences for the superconducting state expected to arise at finite carrier concentrations and should favor a large critical temperature.

Polarons, Bipolarons, and π-Dimers of Bis(3,4-ethylene-dioxythiophene)-(4,4‘-dialkyl-2,2‘-bithiazole)- co-Oligomers. Direct Measure of the Intermolecular Exciton Transfer Interaction

Abstract: The oxidative behavior of bithiazole-ethylenedioxythiophene co-oligomers is described. The acceptor−donor−acceptor (A−D−A) compounds, 5,5‘-bis(4,4‘-dialkyl-2,2‘-bithiazol-5-yl)-(3,4,3‘,4‘-bis(ethylenedioxy)-2,2‘-dithienyl) (1, 2), are sequentially oxidized by NOBF4 through the paramagnetic monocation to the diamagnetic dication. The monocations form diamagnetic π-dimers, the allowed π−π electronic transitions of which are interpreted in terms of molecular exciton theory to give nearest-neighbor exciton coupling constants, J ≅ 0.2 eV. The spectra of the dications show that they are bipolarons; that is, the two charges share a common lattice deformation. The D−A−D co-oligomers, 5,5‘-bis(3,4-ethylenedioxythien-2-yl)-4,4‘-dibutyl-2,2‘-bithiazole (3) and 5,5‘-bis(3,4,3‘,4‘-bis(ethylenedioxy)-2,2‘-dithien-5-yl)-4,4‘-dibutyl-2,2‘-bithiazole (4), are oxidized in a single step to the corresponding bipolarons.