Anisotropic superconductivity in graphite intercalation compound YbC6

TL;DR

This study investigates the anisotropic superconducting properties of YbC6, revealing that its behavior aligns with models for quasi two-dimensional materials, likely due to its thin flake synthesis.

Contribution

It demonstrates that YbC6's upper critical field anisotropy fits quasi-2D models, suggesting a thin-flake structure influences its superconducting behavior.

Findings

Bc2 anisotropy measured via magnetoresistance

Angular dependence fits Lawrence-Doniach or Tinkham models

Sample synthesis as thin flakes affects superconducting properties

Abstract

We report anisotropy of the upper critical field (Bc2) of an intercalated graphite superconductor YbC6 (Tc = 6.5 K) determined from angular dependent magnetoresistance measurements. Though the perpendicular coherence length is much longer than interlayer spacing, measured angular dependences of Bc2 are well fitted by the Lawrence-Doniach model or the Tinkham model, which are known to be applicable to quasi two-dimensional materials or thin films, rather than the effective mass model. This observation is similar to the measurements for the other intercalated graphite superconductor, CaC6, by Jobiliong et al. [E. Jobiliong, H.D. Zhou, J.A. Janik, Y.-J. Jo, L. Balicas, J.S. Brooks, C.R. Wiebe, Phys. Rev. B 76 (2007) 31 052511]. A possible explanation for the unexpected applicability of these models is that our YbC6 samples are synthesized as thin flakes in the host graphite.