Anomalous upper critical field in CeCoIn$_5$/YbCoIn$_5$ superlattices with a Rashba-type heavy fermion interface

We report the precise angular dependence of the upper critical field ($H_{\mathrm{c2}})$ in the epitaxial superlattices CeCoIn$_5(n)$/YbCoIn$_5$(5), formed by alternating layers of $n$ and 5 unit-cells thick CeCoIn$_5$ with a strong Pauli effect and normal metal YbCoIn$_5$, respectively [1]. For the $n =$ 3 superlattice, $H_{\mathrm{c2}}(\theta )$ changes smoothly as a function of the field angle $\theta $. However, near the superconducting transition temperature,$ H_{\mathrm{c2}}(\theta )$ shows a cusp near the angle parallel to the plane of the superlattice. This cusp behavior disappears for $n =$ 4 and 5. This sudden disappearance suggests the relative dominance of the orbital depairing effect in the $n =$ 3 superlattice, which may be due to the suppression of the Pauli effect in a system with local inversion symmetry breaking [2].\\[4pt] [1] Y. Mizukami \textit{et al.}, Nature Phys. \textbf{7,} 849 (2011).\\[0pt] [2] S. K. Goh \textit{et al.}, Phys. Rev. Lett. \textbf{109,} 157006 (2012).