Magnetic-field induced superconductor-metal-insulator transitions in bismuth metal-graphite

Abstract

Bismuth-metal graphite (MG) has a unique layered structure where Bi nanoparticles are encapsulated between adjacent sheets of nanographites. The superconductivity below $T_{c}$ (= 2.48 K) is due to Bi nanoparticles. The Curie-like susceptibility below 30 K is due to conduction electrons localized near zigzag edges of nanographites. A magnetic-field induced transition from metallic to semiconductor-like phase is observed in the in-plane resistivity $\rho_{a}$ around $H_{c}$ ($\approx$ 25 kOe) for both $H$$\perp$$c$ and $H$$\parallel$$c$ ($c$: c axis). A negative magnetoresistance in $\rho_{a}$ for $H$$\perp$$c$ (0$<H\leq$3.5 kOe) and a logarithmic divergence in $\rho_{a}$ with decreasing temperature for $H$$\parallel$$c$ ($H$ $>$ 40 kOe) suggest the occurrence of two-dimensional weak localization effect.