Paraconductivity in layered cuprates behaves as if due to pairing of nearly free quasiparticles

Abstract

We revisit the Aslamazov-Larkin theory of paraconductivity in two dimensions to identify its universal and its specific model-dependent features. We show that both the numerical prefactor and the temperature dependence of the experimental paraconductivity in underdoped La(2-x)Sr(x)CuO(4) provide evidence that the paired carriers behave as if they were nearly free fermionic quasiparticles. This conclusion is strengthened by the analysis of paraconductivity data in the presence of a finite magnetic field. In this case we show that there exists a temperature range above T(c) where the superconducting fluctuations are purely Gaussian and their destruction is determined by a rather low magnetic field scale H(c2)(G)(T=0)

Theory of fluctuation conductivity from interband pairing in pnictide superconductors

“…The paraconductivity along the layers is independent of the in-plane stiffness c ʈ as guaranteed by the same gauge-invariance arguments discussed in Ref. 15 for a single-band superconductor. The leading contributions to paraconductivity along the layers in three and two dimensions ͑3D and 2D, respec-tively͒ take the AL form 12…”

“…We point out that the above expressions are general within a hydrodynamic description of the collective modes and do not rely on any particular assumption about the pairing strength. 15 When the BCS expression for the ⌸ i bubbles holds, m − ͑T͒ = N eff ln͑T / T c ͒ and the dimensionless mass appearing in Eqs. ͑8͒ and ͑9͒ is simply ⑀ = log͑T / T c ͒.…”

Fluctuation spectroscopy: From Rayleigh-Jeans waves to Abrikosov vortex clusters

“…xx passes through a minimum and starts to increase. Such non-monotonic behavior of the conductivity close to H c2 (0) was observed multiple times in experiments (Caprara et al, 2009;Gantmakher et al, 2003;Jin et al, 2008;Leridon et al, 2007). Domain V describes the transition regime between quantum and classical fluctuations, while in domains VI-VII, (along the line H c2 (T )) superconducting fluctuations have already classical character and can be considered in a generalized TDGL scheme, see Ref.…”

Doping-dependent competition between superconductivity and polycrystalline charge density waves

“…The boundary line separating the two latter regions corresponds to an inflection point. The white color thus always corresponds to the superconducting region (either long range or fluctuating), which is the only phenomenon leading to a marked downward curvature [33]. These two maps allow to draw a phase diagram in the (H, T ) plane for each doping, which we illustrate in the three paradigmatic cases of Fig.…”

“…The presence of Cooper pairs is another physical ingredient that should be considered to describe the properties of the pseudogapped state. Although the existence of stable preformed Cooper pairs below T * has been questioned [30,31], measurement of paraconductivity effects in the pseudogap state [30,32,33] show that standard Cooper pair fluctuations are present in a large temperature range above T c .…”