Features of Excess Conductivity Behavior in a Magnetic Superconductor Dy$_{0.6}$Y$_{0.4}$Rh$_{3.85}$Ru$_{0.15}$B$_4$

TL;DR

This study investigates the excess conductivity and pseudogap behavior in a Dy-Y-Rh-Ru-B superconductor, revealing fluctuation regimes, a narrow fluctuation temperature range, and pseudogap features similar to cuprates.

Contribution

First analysis of excess conductivity and pseudogap in Dy-Y-Rh-Ru-B superconductor, identifying fluctuation crossover, pseudogap features, and local pair density.

Findings

Superconducting fluctuations exist within a narrow 2.8 K temperature range.

Pseudogap behavior shows features similar to cuprates below 95 K.

The local pair density near T_c is 1.17 times higher than in YBa2Cu3O7-δ.

Abstract

The temperature dependencies of the excess conductivity $\sigma'(T)$ and possible pseudogap (PG), in a Dy$_{0.6}$Y$_{0.4}$Rh$_{3.85}$Ru$_{0.15}$B$_4$ polycrystal were studied for the first time. It was shown that $\sigma'(T)$ near T$_{c}$ is well described by the Aslamazov Larkin fluctuation theory, demonstrating a crossover with increasing temperature. Using the crossover temperature $T_0$, the coherence length along the c axis $\xi_c(0)$, was determined. Above the level of $T_{2D}>T_{0}$, an unusual dependence $\sigma'(T)$ was found, which is not described by the fluctuation theories in the range from $T_{0}$ to $T_{FM}$, at which a ferromagnetic transition occurs. The range in which superconducting fluctuations exist is apparently quite narrow and amounts to $\Delta T_{fl}=2.8 K$. The resulting temperature dependence of the PG parameter $\Delta^*(T)$ has the form typical of magnetic superconductors with features at $T_{max}=154 K$ and the temperature of a possible structural transition at $T_{s}=95 K$. Below $T_{s}$, dependence $\Delta^*{T}$ has a shape typical for PG in cuprates, which suggests that the PG state can be realized in Dy$_{0.6}$Y$_{0.4}$Rh$_{3.85}$Ru$_{0.15}$B$_4$ in this temperature range. Comparison of $\Delta^*(T)$ with the Peters Bauer theory made it possible to determine the density of local pairs ~0.35, near T$_{c}$, which is 1.17 times greater than in optimally doped YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ single crystals.