Fluctuation Phenomena in Superconductors

Abstract

6. Manifestation of fluctuations in various properties 6.1 The effects of fluctuations on magnetoconductivity 6.2 Fluctuations far from T c or in strong magnetic fields 6.2.1 Fluctuation magnetic susceptibility far from transition. 6.2.2 Fluctuation magnetoconductivity far from transition 6.2.3 Fluctuations in magnetic fields near H c2 (0) 6.3 The effect of fluctuations on the Hall conductivity 6.4 Fluctuations in the ultra-clean case 6.5 The effect of fluctuations on the one-electron density of states and on tunneling measurements 6.5.1 Density of states 6.5.2 The effect of fluctuations on the tunnel current 6.6 Nonlinear fluctuation effects 6.7 The effect of fluctuation on the optical conductivity 6.8 Thermoelectric power above the superconducting transition 6.9 The effect of fluctuations on NMR characteristics 6.9.1 Preliminaries. 6.9.2 Spin Susceptibility. 6.9.3 Relaxation Rate. 7. Conclusions 8. Acknowledgments 9. Bibliography 2 Strictly speaking τ in the most part of future results should be understood as the electron transport scattering time τtr. Nevertheless, as it is well known, in the case of isotropic scattering these values coincide, so for sake of simplicity we will use hereafter the symbol τ.

Electrical Conductivity and Magnetic Susceptibility of Thallium 1223-Based Superconductor in the Fluctuation Range

“…The Ginzburg-Landau mean field theory predicts that ν = 1/3, z = 2, and η = 0. Thus, following the paper [21,22], the dimensionality (d g ) of stochastic (Gaussian) fluctuations can be described as follows For the first region, the closest to the zero resistance critical temperature T c0 , we find that the value of critical exponent λ 1 is 0.23. Assuming that this region is dominated by critical fluctuations [19,20], using (7), we evaluated the dimensionality of the fluctuations in the first region at d c1 = 3.16.…”

“…The classical theory of fluctuations [21,22] predicts that in three-dimensional superconductivity, the excess conductivity can be written as…”

Microscopic theory for a ferromagnetic nanowire/superconductor heterostructure: Transport, fluctuations, and topological superconductivity

“…69 In all these cases, the anomalous peak has been explained using the phenomenon of superconducting fluctuations. 52,53 This phenomenon is concerned with fluctuating Cooper pairs that form while the system is in the normal state but just above the transition temperature T c . The appearance of Cooper pairs above T c opens up a new channel for charge transport.…”

“…In the usual theory of superconducting fluctuations for the bulk of a superconductor, the pair transport contribution (Aslamazov-Larkin contribution) is typically dominant over the DOS contribution and the resistance upturn is not observed. 52 When the Co wire is replaced by a gold wire, the situation is modified. Since gold is not ferromagnetic, singlet correlations are expected to survive over a much longer distance inside the wire.…”

“…The main goal is to provide a perspective on the origin of the resistance peak based on the physics of superconducting fluctuations 52,53 in the W electrodes. We discuss a possible faithful model for the Co nanowire in the vicinity of the deposited W electrodes, develop a microscopic theory for the superconducting fluctuations in the W electrodes, and study how these fluctuations influence the transport through the Co wire.…”