1. Interface Spin Orbit Coupling in a Thin Film Superconductor Philip W. Adams, Louisiana State University, DMR 0204871 We have recently completed a series of experiments investigating the effects of interface spin orbit coupling (ISOC) on conventional BCS superconductivity. ISOC was induced in thin Be films by coating them with ~1 monolayer of Au. Though this had no significant effect on the superconducting transition temperature of the Be, it profoundly changed the spin states of the superconductor and also broke the inversion symmetry of the system. As a consequence, the superconducting bilayers acquired a finite, anisotropic, spin susceptibility. This enhanced the parallel critical field well over the spin-paramagnetic limit, horizontal dashed line in figure. More interestingly, however, the reduced critical field of the Be/Au bilayers scaled as the inverse Be thickness as shown in the figure. This scaling is, in fact, inconsistent with the traditional impurity scattering treatment of spin-orbit coupling. Indeed, we believe that the linear behavior is a manifestation of the superconductor’s attempt to reconcile a mixed-spin boundary condition at the Au interface with the spin- singlet ground state of pure Be. Normalized parallel critical fields as a function of Be thickness for Be/Au bilayers (circles), Be/Pb bilayers (crossed box), and pure Be films (triangles). The long dashed line represents the expected orbital critical field. The horizontal dashed line represents the spin-paramagnetic limiting critical field.

2. Interface Spin Orbit Coupling in a Thin Film Superconductor Philip W. Adams, Louisiana State University, DMR 0204871 Over the last few years we have been studying the behavior of ultra-thin superconductors at extremely low temperatures (50 milliKelvins) and high magnetic fields. We are particularly interested in superconductors that have a low atomic mass, such as aluminum and beryllium. These are essentially classic superconductors in which the current is carried by electrons which have paired together with their spins exactly anti-aligned. By exploiting their spin-symmetry, we can gain insights into the macroscopic quantum mechanical properties of these nearly ideal two-dimensional supercondutors in extreme magnetic fields. More importantly, however, true spin-singlet superconducting films are model systems for investigating a number of phenomena that have important implications for more complex superconductors as well.

3. Field Induced Spin Mixing in Ultra-Thin Superconducting Films Superconducting Films Philip W. Adams, Louisiana State University, DMR 0204871 Education We have had a number of undergraduates contribute to the project over the last few years. David Craig and Andrew Morse were instrumental in upgrading our electron-beam deposition system, and have gained extensive laboratory experience. In addition, Dr. Xiao-Song Wu, joined my group 18 months ago as a post-doctoral associate, and is currently working on the next series of experiments investigating the evolution of superconducting spin states in high magnetic fields. Societal Impact Our research interests have mainly been focused on low dimensional systems that can be treated as being almost ideal. The ultimate goal of the program is to explore the quantum characteristics of well characterized systems, such as the thin aluminum and beryllium films, in extreme environments in order to gain a deeper understanding of the physics of more complex and applicable materials. Our work not only has impact on the condensed matter knowledge base, but also provides an important technological training ground for students and postdocs.