C-axis tunneling in Bi₂Sr₂CaCu₂O_8+δ in the magnetic field up to 60 T

We report on the c-axis resistivity ρc(H) in Bi2Sr2CaCu2O8+β (Bi-2212) that exhibits a maximum in quasistatic magnetic fields up to 60 T. We show that below Tc c-axis tunneling is a parallel, two-channel process: (i) σJ of Cooper pairs and (ii) σq of quasiparticles: σc = σJ + σq. We demonstrate that high-field c-axis conductivity is linear-in-field at H < Hc2, in agreement with the field-linear dependence of quasiparticle conductivity σq we find in mesas. Near 60 T, as temperature decreases, ρc saturates, confirming a gapless spectrum of quasiparticles. The linear ρc(H) behavior extends up to the maximum field in experiment (60T), beyond the applicability of the Fermi-liquid approach, which can be due to effects of the pseudo gap, not accounted in the model. © 2000 Elsevier Science B.V All rights reserved.