| Abstract
| - Intercalation of HgBr2 intoBi2Sr1.5-xLaxCa1.5Cu2Oy(0.0 ≤ x ≤ 0.4) superconductor has been carried outinorder to elucidate the origin of Tc evolutionupon intercalation. The Tc's obtained fromthe dc magneticsusceptibility measurements were plotted against x. Theplot of Tc vs x for the pristinesshowed the parabolicfeature 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 HgBr2intercalates in the overdoped region were reduced less than ∼6 K butincreased by4−6 K in the underdoped one compared with nonintercalated samples.Such changes in Tc uponintercalationindicate hole doping from intercalant to host lattice. An attemptof semiempirical calculation was made todetermine the hole concentration doped by intercalation. UponHgBr2 intercalation, the amount of hole dopingwas estimated to be ∼0.2 hole per formula unit of the sample withx = 0.0, whereas the doping of ∼0.3 holewas estimated for the iodine intercalated sample. Considering theTc depression (ΔTc) andlattice expansion(Δd) between the iodine intercalate(ΔTc ≈ 10 K and Δd ≈ 3.6 Å)and the HgBr2 one (ΔTc ≈ 6 K andΔd≈ 6.3 Å), it can be concluded that the change inTc upon intercalation clearly depends on thehole concentrationdue to the charge transfer between host and guest, rather than theinterblock electronic coupling due to thelattice expansion.
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