The dependence of the interlayer quasiparticle conductivity, s _q, on the magnetic field, B, is calculated for Josephson coupled layered d-wave superconductors. This conductivity may be measured in stacks of small-area cuprate layers (mesas) in the resistive state, where interlayer supercurrent is negligible. In our calculations we assume that the contribution of coherent electron tunneling (with conservation of the in-plane momentum) to the c-axis tranport is dominant and the scattering of electrons inside layers is resonant and in the clean limit.

For B ½ ½ c the effect of vortices on s _q is accounted for within the semiclassical (Doppler shift) approach. When pancake vortices are weakly correlated in adjacent layers (as in the Bi₂Sr₂CaCu₂O₈ superconductor above 0.05 T) at low temperatures s _q increases sharply with B on the scale Bg =F ₀g ²/h²n 2_F, where g is the effective scattering rate of quasiparticles. At BD >> B > Bg interlayer conductivity reaches an extended region of slow linear growth on the scale BD =F ₀D ²₀/h²n 2_F, where D ₀ >> g is the gap amplitude. At high T >> g interlayer conductivity initially drops and then reaches the same linear regime. The linear regime of quasiparticle interlayer conductivity on the scale BD is due to compensation, on the scale Bg , between the increase of the quasiparticle DOS with B due to vortices and the increase with B of the effective scattering rate at tunneling due to disorder in pancake positions in adjacent layers. For corelated pancakes s _q increases almost linearly with B on the scale Bg at all B << BD .

For B ½ ½ ab due to the Zeeman effect the interlayer conductivity at low T increases linearly with field B << D ₀/m _B on the scale Bp=g /m _B where m _B is the Bohr magneton.

We studied the c-axis transport in high quality mesa-type structures fabricated by focused ion beam (FIB) technique from Bi-2212 single crystal whiskers. We found out that interlayer tunneling I-V characteristics at low temperatures essentially differ frome those of conventional Josephson junctions between s-wave superconductors. We specify strong disagreement with the Ambegaokar- Baratoff (A-B) relation, quadratic temperature and bias voltage dependences of the quasiparticle tunneling conductivity s _q(T,V), nonzero and universal value of s _q(0,0). We found empirically a modified relation of the A-B type and scaling relation between s _q(0,V) and s _q(T,0) dependences. We showed that all these features can be described self-consistently by Fermi-liquid model for quasiparticles in clean d-wave superconductor with resonant scattering. Our analysis points out to significant coherency of interlayer tunneling for both quasiparticles and Cooper pairs.

We study Josephson plasma resonance (JPR) in Bi₂Sr₂CaCu₂O_8+y single crystals fabricated into mesa array with sizes from 20x20 m m² to 100x100 m m². The mesa array are fabricated on Bi₂Sr₂CaCu₂O_8+y single crystals of approximate dimensions of 0.6x0.4x0.015 mm³ using Ar-ion milling. The mesa heights are more than a half of the original crystal thickness and the volumes of the substrate crystal and the mesa array are comparable. JPR is measured by cavity perturbation method at 24 and 42 GHz. At lower temperatures, additional resonance peaks are observed at fields 20 % higher than the main resonance peaks. The fact that we observe two separate resonance peaks in a crystal with mesa array shows that the average of phase coherence <cos f _n, _n+1> (f _n, _n+1: gauge invariant phase difference between n th and n+1 th layer), which is proportional to the resonance frequency squared, is determined by the local average of cos f _n, _n+1 rather than a global average over the entire sample, consistent with the theoretical estimate of the length scale for a variation of the phase cohrence of about 1 m m. Both resonance peaks show characteristic temperature dependence of the decoupled liquid state. The relative intensities of the minor peaks to the main peaks range from 5% to 50%, and depend on doping level and temperature rather than the size of the mesa. The origin of the minor resonance peak and its relation to the vortex matter state will be discussed.

We report on the c-axis resistivity r _c(H) in Bi₂Sr₂CaCu₂O₈₊d (Bi-2212) that peaks in quasi-static magnetic fields up to 60 T. We show that a key to understanding of this dependence is the realization that below T_c c-axis tunneling is a parallel, two-channel process: (i) s _J of Cooper pairs (mostly at low fields) and (ii) sq of quasiparticles (dominant at higher fields): s _c=s _J+s _q. Whereas the field dependence of Josephson tunneling is described theoretically by A. Koshelev, providing a power law for s _J(H), at present there is no theory for the high-field quasiparticle tunneling. We access quasiparticle current by suppressing the Josephson current in two ways: (i) with transport current in thin Bi-2212 mesas, and (ii) with a 60 T field, which in underdoped Bi-2212 crystals exposes quasiparticle tunneling down to ~22 K. We demonstrate that high-field c-axis conductivity is linear-in-field at H<H_c2, in agreement with the field-linear dependence of quasiparticle conductivity s q we find in mesas. Near 60 T, as temperature decreases, r _c saturates, confirming a gapless spectrum of quasiparticles. Although r _c can be consistently described at low energy within the Fermi-liquid picture, the H-linear dependence extends into regions of H, T beyond the model applicability. The pseudo gap, not included in the model, is believed to be responsible.