Superconductor-insulator transition tuned by annealing in Bi-film on top of Co-clusters

作者：Herrera W T^*; Dinola I S; Continentino M A; Micklitz H; Xing Y T; Fontes M B; Baggio Saitovitch E

来源：European Physical Journal B, 2013, 86(12): 508.

DOI：10.1140/epjb/e2013-40337-3

We deposited amorphous Bi films with a thickness between 3 and 6.5 nm at 4.2 K on top of previously deposited Co clusters having a mean size of similar to 4.5 nm. The Co cluster layers thickness was between 2.3 and 5 nm. In-situ electrical transport measurements were performed between 2 and 100 K. Measurements on as-prepared samples having a Bi layer thickness of 3.0 nm show hopping (tunneling) conductivity as sigma(T) = sigma(0) exp[-(T-0/T)(1/2)] above the superconducting transition temperature T-C and re-entrance behavior again with hopping (tunneling) conductivity below T-C. Annealing of films having a Bi layer thickness of 5.5 nm results in a decrease of resistivity, with variable-range hopping conduction behavior as sigma(T) = sigma(0) exp[-(T-0/T)(1/3)]. Quite different are the findings for films having a Bi layer thickness of 6.5 nm: annealing of these films results in a power-law behavior as sigma(T) = sigma T-0(alpha) with alpha = 2/3, indicating that these films are close to a quantum critical point separating superconducting and insulating phases. A phase diagram including all experimental observations is proposed.

• 出版日期2013-12-16