Short-wavelength cutoff effects in the ac fluctuation conductivity of superconductors

Abstract

The short wavelength cutoff has been introduced in the calculation of ac fluctuation conductivity of superconductors. It is shown that a finite cutoff leads to a breakdown of the scaling property in frequency and temperature. Also, it increases the phase φ of the complex conductivity (tan φ = σ2/σ1) beyond π/4 at Tc. Detailed expressions containing all essential parameters are derived for 3D isotropic and anisotropic fluctuation conductivity. In the 2D case we obtain individual expressions for the fluctuation conductivity for each term in the sum over discrete wavevectors perpendicular to the film plane. A comparison of the theory to the experimental microwave fluctuation conductivity is provided.

Critical fluctuations and pseudogap observed in the microwave conductivity ofBi2Sr2CaCuPeligrad1, Mehring2, Dulčić3 2004Phys. Rev. BSelf Cite122100View full textAdd to dashboardCite

“…The analytical result of the integration in Eq. (1) and its application in the data analysis has been reported in detail 23 . A careful analysis has shown that, due to this cutoff, the real and imaginary parts of the ac fluctuation conductivity are not equal at T c .…”

“…Note that we have used here the thermodynamically correct form k B T , rather than the approximative k B T c used before 23 . The latter will be used below only in theoretical simulations where ξ(T )/ξ 0 is used as the only variable.…”

“…This dimensionless temperature dependent function is equal for both, the in-plane and c-axis coherence lengths, i. e. (ξ ab (T )/ξ 0ab ) = (ξ c (T )/ξ 0c ), 23 so that we omit the subscripts. The dimensionless parameter…”

“…(3) vanishes and one retrieves the pure wavevector cutoff condition. With the constraint ensuing from the experimental ratio σ 2 (T c )/σ 1 (T c ), 23 and Eq. (3) with a given energy cutoff parameter C, one can determine the Λ's at T c .…”

“…In this paper, we use the expressions for the ac fluctuation conductivity which have been derived and extensively discussed recently 23 . The derivation was based on the time dependent Ginzburg-Landau theory and the approach introduced by Schmidt 25 long time ago.…”