Do organic and other exotic superconductors fail universal scaling relations?

Abstract

Universal scaling relations are of tremendous importance in science, as they reveal fundamental laws of nature. Several such scaling relations have recently been proposed for superconductors; however, they are not really universal in the sense that some important families of superconductors appear to fail the scaling relations, or obey the scaling with different scaling pre-factors. In particular, a large group of materials called organic (or molecular) superconductors are a notable example. Here, we show that such apparent violations are largely due to the fact that the required experimental parameters were collected on different samples, with different experimental techniques. When experimental data is taken on the same sample, using a single experimental technique, organic superconductors, as well as all other studied superconductors, do in fact follow universal scaling relations.

In-plane superfluid density and microwave conductivity of the organic superconductorκ-(BEDT-TTF)2Cu[N(CN)2]Br: Evidence forMilbradt1, Bardin2, Truncik3 et al. 2013Phys. Rev. B354461View full textAdd to dashboardCite

“…60,61 A similar analysis carried out on previously published data, [26][27][28][29][47][48][49][50] in which ρ s (T ) is 4 to 40 times smaller, predicts vortex unbinding in the range 3 to 8 K. This is not observed. Finally, our data have recently been shown to be consistent 62 with the Homes scaling law 63 relating superfluid density to the product of normal-state conductivity and T c .…”

S-wave superconductivity in anisotropic holographic insulators

“…To convert to a dimensionless unit system used in be almost the arithmetic mean of the two experimentally determined values. Additionally, one may compare to the most recent results found for organic superconductors in [57], i.e. C = (110 ± 60) cm −1 /Ω −1 K, again in dimensionful units.…”

FeTe0.55Se0.45: A multiband superconductor in the clean and dirty limit

“…Initially, it was thought that the materials that fell on the scaling line were likely in the dirty limit [37]. However, it has been shown that many superconducting materials fall on the scaling line, and many of them are not in the dirty limit [72]. Moreover, it has been recently demonstrated that the scaling relation is more robust than originally thought and should be valid for most materials, including those that approach the clean limit [38], suggesting that the scaling relation is an intrinsic property of the BCS theory of superconductivity.…”