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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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Journal ArticleDOI
TL;DR: In this article, it was shown that a giant drop in the number of current carriers during the transition, which is a consequence of bipolaron formation in the paramagnetic phase, is extremely sensitive to an external magnetic field.
Abstract: An exchange interaction of polaronic carriers with localized spins leads to a new ferromagnetic transition in doped charge-transfer insulators with strong electron–phonon coupling. The relative strength of the exchange and electron–phonon interactions determines whether the transition is first or second order. A giant drop in the number of current carriers during the transition, which is a consequence of bipolaron formation in the paramagnetic phase, is extremely sensitive to an external magnetic field. We show that the carrier density collapse describes the colossal magnetoresistance, anomalous specific heat, and tunneling gap of doped manganites close to the transition. The dependence of the binding energy on ion mass explains the giant isotope effect in magnetization and resistivity upon substitution of 16O by 18O.

7 citations

Book ChapterDOI
01 Jan 2000
TL;DR: In this paper, the structural properties of small electron polarons, based on EPR studies, in BaTiO3, WO3 and LiNbO3 are presented.
Abstract: Mobile charge carriers moving among equivalent sites in polar crystals tend to form polarons. Their properties are determined by the interplay between symmetry breaking interactions, such as coupling to the lattice and potential fluctuations, and those which are symmetry restoring, such as tunneling between equivalent neighbors. Polarons are classified by the alternatives ‘small – large’, ‘electron – hole’, ‘single polaron – bipolaron’, ‘free – bound’. Information on the structural properties of small electron polarons, based on EPR studies, in BaTiO3, WO3 and LiNbO3 is presented. On this firm basis some of the optical features of the polarons are interpreted. In all three cases there are indications for the presence of bipolarons also. An important polaron subclass are O- hole polarons bound to acceptor defects in perovskite crystals. Their properties, especially the optical ones, are discussed in comparison to those of free polarons.

7 citations

Journal ArticleDOI
TL;DR: In this article, a quasi-0D quantum dot with a spherical parabolic confinement potential was investigated by applying the Feynman variational principle and the bipolaron coupling energy and self-action potential energy were found to increase with an increase in the Frohlich electron-phonon-coupling constant.

7 citations

Journal ArticleDOI
TL;DR: In this paper, the Bose condensation of bipolarons is considered to be valid as the origin of superconductivity in the normal phase of La 2-x Sr x CuO 4.
Abstract: The feature of the electrical resistivity in the normal phase of La 2- x Sr x CuO 4 is explained by the coexistence model of Anderson localization and small polarons. The estimated concentration of the small polarons from this model attains a maximum at the optimum concentration, where the superconducting transition temperature attains its maximum. The variation of the activation energy of the hopping conduction with x is explained by taking into account the transfer mechanism accompanied with a change of states between Anderson localization and a small polaron state. From this analysis the Bose condensation of bipolarons is considered to be valid as the origin of superconductivity in this material.

7 citations

Journal ArticleDOI
TL;DR: In this paper, the ground state of bipolarons with spin-orbit coupling in a quantum dot (QD) was studied using the Lee-Low-Pines-Tokuda variational method.
Abstract: The properties of the ground state of bipolarons with Rashba spin-orbit (SO) coupling in a quantum dot (QD) are studied by using the Lee-Low-Pines-Tokuda variational method. The results of numerical calculation indicate that the condition to form the stable bipolaron structure in the QD (binding energy E b > 0) is naturally satisfied with the electron-phonon strong coupling (coupling constant α > 6). The binding energy of bipolarons E b increases with the increase of the confinement strength ω 0 of the QD, electron-phonon coupling strength α, Coulomb bound potential β and velocity u of polarons. The ground energy of bipolarons E splits into E(+) and E(−), corresponding to spin both “up” and both “down” of two electrons, respectively, and $\left | {E(-)} \right |>\left | {E(+)} \right |$ . The grouenergy of bipolarons E in the QD is composed of the electron-phonon coupling energy E e-ph, confinement potential of the QD E couf, Coulomb energy between two electrons E coul and Rashba SO coupling energy E SO. E e-ph is always negative and plays a dominant role. The weights of E coul and E couf are only next to E e-ph. Though the weight of the Rashba SO coupling energy E SO is the smallest one, it can influence other parts of the ground-state energy through interacting with the phonon. Therefore, the bipolaron effect and Rashba SO coupling must not be ignored when investigating the QD.

7 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202316
202229
202127
202023
201920
201833