H– T phase diagram and the nature of vortex-glass phase in a quasi-two-dimensional superconductor: Sn-metal layer sandwiched between graphene sheets

The magnetic properties of a quasi-two-dimensional (2D) superconductor, Sn-metal graphite (MG), are studied using DC and AC magnetic susceptibility. Sn-MG has a unique layered structure where Sn metal layer is sandwiched between adjacent graphene sheets. This compound undergoes a superconducting transition at T c=3.75 K at H=0. The H– T diagram of Sn-MG is similar to that of a quasi-2D superconductors. The phase boundaries of vortex liquid, vortex glass, and vortex lattice phase merge into a multicritical point located at T ∗=3.4 K and H ∗=40 Oe. There are two irreversibility lines denoted by H gl (de Almeida–Thouless type) and H gl ′ (Gabay–Toulouse type), intersecting at T 0 ′=2.5 K and H 0 ′=160 Oe. The nature of slow dynamic and nonlinearity of the vortex glass phase is studied.