A Superconductor in the Presence of an Exchange Field and Spin-orbit Interaction

A superconductor (SC) in contact with a magnetic semiconductor experiences a large internal exchange field (IEF) that acts on the spins [1,2]. The quasi particle density of states (\textit{q-DOS}) in the SC splits by the Zeeman energy, 2$\mu $H$_{EX}$ where $\mu $ is the electron magnetic moment and H$_{EX}$ is the IEF [1,2]. Here we combine IEF and spin-orbit (S-O) interaction to investigate the properties of Al by superconductive (SIS) tunneling spectroscopy [1]. Thin film sandwich junction 4EuS/4.5Al/($d$-Au)/Al$_{2}$O$_{3}$/8Al (film thickness in nm and $d$ from 0 to 0.06nm) was studied: ferromagnetic EuS layer provides the IEF whereas the Au layer creates the S-O scattering in Al. Tunnel conductance measured at 0.4K showed a large Zeeman splitting of \textit{q-DOS} in Al film due to the IEF, even at H$_{appl}$ = 0. In zero H the large asymmetry in the conductance peaks and reduction in the Zeeman splitting were observed due to S-O scattering when compared to control junctions (no Au). The sharp features in the SIS tunnel conductance allowed these studies even at the lowest level of S-O scattering.\\[4pt] [1] R. Meservey and P. M. Tedrow, Phys. Rep. 238, 173 (1994).\\[0pt] [2] J. S. Moodera, T. S. Santos and T. Nagahama, J. Phys.: Condens. Matter 19, 165202 (2007)