Intercalation of HgBr2 into Bi2Sr1.5-xLaxCa1.5Cu 2Oy (0.0 ≤ r ≤ 0.4) superconductor has been carried out in order to elucidate the origin of Tc evolution upon intercalation. The Tc's obtained from the dc magnetic susceptibility measurements were plotted against x. The plot of Tc vs x for the pristines showed the parabolic feature with overdoped (0.0 ≤ x < 0.1), optimally doped (x = 0.1), and underdoped (0.2 ≤ x ≤ 0.4) regions. The Tc's of the HgBr2 intercalates in the overdoped region were reduced less than ∼6 K but increased by 4-6 K in the underdoped one compared with nonintercalated samples. Such changes in Tc upon intercalation indicate hole doping from intercalant to host lattice. An attempt of semiempirical calculation was made to determine the hole concentration doped by intercalation. Upon HgBr2 intercalation, the amount of hole doping was estimated to be ∼0.2 hole per formula unit of the sample with x = 0.0, whereas the doping of ∼0.3 hole was estimated for the iodine intercalated sample. Considering the Tc depression (ΔTc) and lattice expansion (Δd) between the iodine intercalate (ΔTc ≈ 10 K and Δd ≈ 3.6 Å) and the HgBr2 one (ΔTc ≈ 6 K and Δd ≈ 6.3 Å), it can be concluded that the change in Tc upon intercalation clearly depends on the hole concentration due to the charge transfer between host and guest, rather than the interblock electronic coupling due to the lattice expansion.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry