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.

Pseudogap in high-temperature superconductors from realistic Fröhlich and Coulomb interactions

Abstract: It has been recently shown that the competition between unscreened Coulomb and Frohlich electron-phonon interactions can be described in terms of a short-range spin exchange Jp and an effective on-site interaction in the framework of the polaronic t-Jp- model. This model, that provides an explanation for high-temperature superconductivity in terms of Bose-Einstein condensation (BEC) of small and light bipolarons, is now studied as a charged Bose-Fermi mixture. Within this approximation, we show that a gap between bipolaron and unpaired polaron bands results in a strong suppression of low-temperature spin susceptibility, specific heat and tunnelling conductance, signalling the presence of a pseudogap regime in the normal state without any assumptions on pre-existing orders or broken symmetries in the normal state of the model.

Polaron Pairing in Multi‐Layer Structures: II. Interlayer Bipolaron States in Structures with Quantum Wells

Abstract: A structure containing conductive planes separated by polar dielectric interlayers is shown to possess the possibility to create bipolaron states by charge carriers moving in the different planes. The attraction is due to the inertial polarization induced by similar charges in polar interlayers which separate them from each other (interlayer polaron pairing). The potential energy of electron-electron interaction and the bipolaron binding energy are calculated as functions of material and geometric parameters of the structure. [Russian Text Ignored].

Adiabatic theory for the bipolaron

Abstract: A translation-invariant adiabatic theory is constructed for the bipolaron. It is shown that motions in the bipolaron are divided: the relative electron coordinates describe fast electron oscillations in the induced polarization well and the center of mass coordinates represent slow electron movement followed by polarization. Nonlinear differential bipolaron equations are derived which are asymptotically exact in the adiabatic limit. Particlelike solutions of these equations correspond to the bipolaron bound state. The exact solution yields the value of the ion critical parameter \ensuremath{\eta}=0.31 for which the bipolaron state is stable, where \ensuremath{\eta}=${\mathrm{\ensuremath{\epsilon}}}_{\mathrm{\ensuremath{\infty}}}$/${\mathrm{\ensuremath{\epsilon}}}_{0}$ and ${\mathrm{\ensuremath{\epsilon}}}_{\mathrm{\ensuremath{\infty}}}$,${\mathrm{\ensuremath{\epsilon}}}_{0}$ are high-frequency and static dielectric permittivities. The energy, the total energy, the effective mass, the radius, and the critical values of the electron-phonon coupling constants are calculated for the bipolaron. The results obtained are generalized to the case of two-dimensional bipolarons.

Translation Invariant Bipolaron Theory of Superconductivity and Spectroscopic Experiments

Abstract: The explanation of the nature of superconducting gap in high temperature superconductors (HTSC) is a fundamental task which solution can lead to the understanding of superconducting mechanism. However, it has not been fully solved yet. From the mid of the twentieth century when Bardeen, Cooper and Schrieffer constructed their theory it has been believed that a superconducting gap is a collective phenomenon of electron excitations. In this work it is demonstrated that according to translation-invariant bipolaron theory of HTSC the different types of experiments measure for the gap different values. Thus tunneling experiments determine the bipolaron energy for a superconducting gap. On the other hand, the angle - resolved photoemission spectroscopy method measures the phonon frequency for which the electron-phonon interaction is maximum. Such effects as kinks in spectral measurements of gap, its angular dependence, existence of pseudogap and others have got natural explanations.