Growth and anisotropy evaluation of NbBiCh3 (Ch = S, Se) misfit-layered superconducting single crystals

Local structure of Nb in superconducting Nb-doped Bi2Se3

“…The reduced Bi content in the S2 synthesis may have encouraged a smaller value of δ in the misfit phase. A smaller value of δ gives a smaller T c according to Nagao et al [48]. However, it remains an unanswered question whether a variation in the misfit stoichiometry, disorder, or defect structure can bring about a reduction in the T c as significant as the one we report for S2.…”

“…Perfectly stoichiometric cases will have a specific value of δ, and for (BiSe) 1+δ NbSe 2 , this value is δ = 0.1. Recently, Nagao et al [48] showed that large variations in the stoichiometry are possible, and that the superconducting transition temperature is varied in response. They found a T c of 2.4 K for δ = 0 and 3.2 K for δ = 0.33 (the latter was reported as Nb 0.9 Bi 1.2 Se 3 ).…”

Structural and electronic inhomogeneity of superconducting Nb-doped Bi2Se3

“…Recently, an increase in T C for (BiSe) 1+δ (NbSe 2 ) was reported by Nagao et al [47]. They grew single crystals and observed T C 's of 2.4 and 3.2 K for nominal compositions of δ = 0 and δ = 0.33, respectively.…”

Characterizations of Anisotropic Superconductivity in (BiSe)1+δNbSe2

“…Single crystals of (BiSe)1+δNbSe2 were synthesized by CsCl/KCl flux method as described in ref. [3]. For the raw materials, high purity fine powders of Bi (99.999%), Se (99.999%), and Nb (99.5%) were used.…”

“…Among various MLCs family, (BiSe)1.10NbSe2, sometimes referred to as BiNbSe3, is known to show superconductivity with the critical temperature Tc of 2.3 ~ 3.3 K [2,3]. Recently, there are some reports claiming that the superconductivity of NbxBi2Se3, a material that Nb atoms are doped into a topological insulator Bi2Se3, is identical to the misfit phase (BiSe)1.10NbSe2 [4,5].…”