Vortices and Quasiparticles near the Superconductor-Insulator Transition in Thin Films

We study the low temperature behavior of an amorphous superconducting film driven normal by a perpendicular magnetic-field ($B$). For this purpose we introduce a new two-fluid formulation consisting of fermionized field-induced vortices and electrically neutralized Bogoliubov quasiparticles (spinons) interacting via a long-ranged statistical interaction. This approach allows us to access a novel non-Fermi-liquid phase, which naturally interpolates between the low $B$ superconductor and the high $B$ normal metal. We discuss the properties of the resulting “vortex metal” phase.

Figure 1

Schematic $T=0$ phase diagram of amorphous superconducting films in the two-fluid model, as a function of an applied magnetic field. Dashed curves label the vortex conductivity and spinon resistivity, which determine, via Eq. (9), the electrical resistance (solid line). The vortex metal phase separates the low field superconductor ($B<B_2$) from the high field Fermi liquid ($B>B_3$).