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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01 Jan 1994
TL;DR: In this article, the BCS theory of superconductivity has been generalized to the strong coupling regime, where spin polarons and bipolarons have been shown to have superconducting properties.
Abstract: Chapter 1 Superfluid Liquid Helium and Weakly Interacting Bose-gas: Bose- Einstein condensation and neutral superfluids He4 and He3 Charged bosons in two dimensions. Chapter 2 BCS Theory of Superconductivity: BCS ground state and excitation spectrum Hallmark indicators of BCS superconductivity. Chapter 3 Intermediate-coupling Generalisation of the BCS Theory: Effects of the electron-phonon interaction in a normal metal Migdal approach Intermediate coupling superconductivity Eliashberg theory. Chapter 4 Many Polaron Problem: Breakdown of the Migdal approach in the strong-coupling regime Canonical transformation and exact eigenstates in the strong-coupling limit Spin polarons and bipolarons. Chapter 5 Strong-coupling Bipolaronic Superconductivity: Polaronic superconductivity Bipolaronic superconductivity. Chapter 6 Non-Fermi Liquid Features of High-Tc Oxides and some Theoretical Proposals. Chapter 7 The Bipolaron Theory of High-Tc Metal Oxides: Earlier indications for mobile polarons and bipolarons in oxides Effect of the Bose-Einstein condensation on the infrared absorption Superconducting state thermodynamics and kinetics. Part contents.
1 citations
TL;DR: In this paper, a theory for spin-polarized transport through a generic organic polymer connected to ferromagnetic leads with arbitrary angle between their magnetization directions is presented, taking into account the polaron and bipolaron states as effective charge and spin carriers.
Abstract: We present a theory for spin-polarized transport through a generic organic polymer connected to ferromagnetic leads with arbitrary angle ? between their magnetization directions, taking into account the polaron and bipolaron states as effective charge and spin carriers. Within a diffusive description of polaron?bipolaron transport including polaron?bipolaron conversion, we find that the bipolaron density depends on the angle ?. This is remarkable, given the fact that bipolarons are spinless quasiparticles, and opens a new way to probe spin accumulation in organic polymers.
1 citations
TL;DR: In this article, the authors used the bipolaron model to analyze the normal state resistivity versus temperature in high temperature superconductor with the addition of ferromagnetic nanoparticles of Pr 2 Co 7.
Abstract: Samples with the addition of ferromagnetic nanoparticles of Pr 2 Co 7 on YBa 2 Cu 3 O y (YBCO) polycrystalline superconductor were prepared by the standard solid state reaction method. The analysis of x-ray diffraction patterns by Rietveld refinement indicates orthorhombique to tetragonal phase transformation and oxygen rate reduction from x=0.3% of Pr 2 Co 7 content. Resistivity at room temperature increases as Pr 2 Co 7 content increases. The normal state resistivity versus temperature was analyzed properly by the bipolaron model. It suggested the increase of mobile charge localization with Pr 2 Co 7 content. Keywords: Pr 2 Co 7 ferromagnetic nanoparticles, high temperature superconductor, bipolaron model, localization of mobile charge
1 citations
TL;DR: In this article, the bipolaron array makes a pinned charge density wave (CDW) along b -axis, and the ratio of the oscillator mass m ∗ CDW to the free electron mass m was determined to be 5 × 10 2.
1 citations
01 Jan 1993
TL;DR: In this article, the role of quantum lattice fluctuations in the case of phonon softening was analysed and it was shown that strong quantum character of these resonant bipolarons could prevent their localization into real space structures which could be insulating Bipolaronic charge density wave (BCDW) or PSDWs, then favouring the formation of superconducting coherent states with a possible high Tc.
Abstract: At large enough electron phonon coupling, the existence of bipolaronic, polaronic and mixed states is rigourously proven for the adiabatic Holstein model at any dimension and any band filling1. The ground-state is one of them which then prove the existence of insulating Bipolaronic Charge Density Waves (BCDW). The role of the quantum lattice fluctuations is analysed and found to be negligible in that regime but to become essential in case of phonon softening then favouring the occurrence of superconductivity2, 3. When a strong Hubbard term is also present, the bipolarons break into polarons and the ground state is expected to be a Polaronic Spin Density Wave (PSDW). If the repulsive Hubbard term is comparable to the electron-phonon coupling, the energy for breaking a bipolaron into two polarons can become small and we get instead of these two degenerate structures, a pair of polarons bounded by a spin resonance which we call “spin resonant bipolaron”. This resonant bipolaron is still strongly bound, but the role of the quantum lattice fluctuations becomes now very important and yields a sharp broadening of the band width of this resonant bipolaron. Thus, the strong quantum character of these resonant bipolarons could prevent their localization into real space structures which could be insulating BCDWs or PSDWs, then favouring the formation of a superconducting coherent state with a possible high Tc.(For details see ref. 4)
1 citations