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: The electrical conductivities of boron carbides, B{sub 12+x}C{sub 3{minus}x} with 0.1 < x < 1.7, between 300 and 1200K suggest the hopping of a nearly temperature-independent density of small polarons as mentioned in this paper.
Abstract: The electrical conductivities of boron carbides, B{sub 12+x}C{sub 3{minus}x} with 0.1 < x < 1.7, between 300 and 1200K suggest the hopping of a nearly temperature-independent density of small (bi)polarons. The activation energies of the nobilities are low, {approx} 0.16 eV, and are nearly independent of the composition. At lower temperatures, conductivities have non-Arrhenius temperature dependencies and strong sensitivity to carbon concentration. Percolative aspects of low-temperature hopping are evident in this sensitivity to composition. Boron carbides' Seebeck coefficients are anomalous in that (1) they are much larger than expected from boron carbides' large carrier densities and (2) they depend only weakly on the carrier density. Carrier-induced softening of local vibrations gives contributions to the Seebeck coefficient that mirror the magnitudes and temperature dependencies found in boron carbides.
8 citations
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TL;DR: In this article, the positron annihilation lifetime (PAL) spectroscopy, conductivity and electron spin resonance (ESR) measurements were used for the analysis of polypyrrole.
Abstract: Microstructural defects (polarons, bipolarons), responsible for conduction in polypyrrole (PPy) has been studied using positron annihilation lifetime (PAL) spectroscopy, conductivity and electron spin resonance (ESR) measurements. Pyrrole, oxidized at different oxidizing strengths [0.13(N)–2.0(N)] by ammonium ferric sulphate has been used for the preparation of PPy. It is observed from the PAL measurement that of the two lifetime components the longer one originates from annihilation of positron in the defect (polaron and bipolaron) sites and the corresponding intensity is a measure of the defect concentration. Further it is evident from the ESR spectra that the dominant defects are polarons at lower oxidizing strengths [⩽ 0.75(N)] and bipolarons at strengths ⩾ 1.0(N). Conductivity data corroborate the findings.
8 citations
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TL;DR: In this paper, it was shown that a two-center Frohlich bipolaron can exist if the ration of the optic and static dielectric constant satisfies a simple realistic inequality.
8 citations
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TL;DR: In this paper, the authors reported an even further example of the experimental data of the Ca-Sr-Bi-Cu-O system amazingly similar to those of the Ba-Pb-BiO system.
Abstract: Quite recently, we reported a preliminary part of the experimental results of “ the Novel Spectral Photoconductivity of the Ba-Pb-Bi-O System potentially correlative with Superconductivity ”. Here, we report an even further example of the preliminary part of the experimental data of the Ca-Sr-Bi-Cu-O system amazingly similar to those of the Ba-Pb-Bi-O system rather than those of the La-Cu-O, Y-Cu-O or Y-Ba-Cu-O systems. These results suggest the undisputed importance of “the exciton-mediated bipolaron mechanis” mainly in the Bi 2 O 3 -like part in the Ca-Sr-Bi-Cu-O system.
8 citations
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TL;DR: In this paper, the existence of the characteristic bound state of bipolarons (a dimerized electron pair of up and down spins on the near neighbor sites) was established by NMR and X ray diffraction measurements in the quasi-1-d conductor MxV205(M= Na,Ag,Li,Cu, and Pb).
Abstract: The existence of the characteristic bound state of BIPOLARON (a dimerized electron pair of up and down spins on the near neighbour sites) was established by NMR and X ray diffraction measurements in the quasi-1-d conductor MxV205(M= Na,Ag,Li,Cu, and Pb). On the basis of the results of EPR and NMR relaxation, the observed high electrical conductivity along the 1-d axis is interpreted as the COLLECTIVE MOTION of BIPOLARONS. These characteristic properties are discussed with the strong electron-phonon interaction of the rather well localized small polarons in the 3d vanadium bronzes, which is different from the 4d. molybdenum bronzes.
8 citations