N. Morozov

High-field quasiparticle tunneling in Bi2Sr2CaCu2O(8+delta): negative magnetoresistance in the superconducting state

We report on the c-axis resistivity rho(c)(H) in Bi(2)Sr(2)CaCu(2)O(8+delta) that peaks in quasistatic magnetic fields up to 60 T. By suppressing the Josephson part of the two-channel (Cooper pair/quasiparticle) conductivity sigma(c)(H), we find that the negative slope of rho(c)(H) above the peak is due to quasiparticle tunneling conductivity sigma(q)(H) across the CuO2 layers below H(c2). At high fields (a) sigma(q)(H) grows linearly with H, and (b) rho(c)(T) tends to saturate ( sigma(c) not equal0) as T-->0, consistent with the scattering at the nodes of the d-wave gap. A superlinear sigma(q)(H) marks the normal state above T(c).

STRUCTURE OF VORTEX LIQUID PHASE IN IRRADIATED BI2SR2CACU2O8-DELTA CRYSTALS

The c-axis resistivity in irradiated and in pristine BSCCO(2212) crystals is measured as a function of the in-plane magnetic field component at fixed out-of-plane component B_\perp in the vortex liquid phase at T=67 K. From this data we extract the dependence of the phase difference correlation length inside layers on B_\perp and estimate the average length of pieces of vortex lines confined inside columnar defects as a function of the filling factor f=B_\perp / B_\phi. The maximum length, about 15 interlayer distances, is reached near f=0.35.

Interlayer tunneling of quasiparticles and cooper pairs in Bi-2212 single crystal whiskers

Abstract The interlayer tunneling has been studied on high quality Bi-2212 stacks of micron to the submicron lateral size. We found that low temperature and low voltage tunneling I–V characteristics can be self-consistently described by Fermi-liquid model for a d -wave superconductor with a significant contribution from coherent interlayer tunneling. The gap and pseudogap interplay with variation of temperature and magnetic field has been extracted from the I–V characteristics. We consider also the role of charging effects for submicron stacks.

Quasiparticle and Cooper pair tunneling in the vortex state ofBi2Sr2CaCu2O8+δ

From measurements of the c-axis I-V characteristics of intrinsic Josephson junctions in Bi_2Sr_2CaCu_2O_{8+delta} (Bi-2212) mesas we obtain the field dependence (H || c) of the quasiparticle (QP) conductivity, sigma_q(H,T), and of the Josephson critical current density, J_c(H,T). The quasiparticle conductivity sigma_q(H) increases sharply with H and reaches a plateau at 0.05 T <H< 0.3 T. We explain such behavior by the dual effect of supercurrents around vortices. First, they enhance the QP DOS, leading to an increase of sigma_q with H at low H and, second, they enhance the scattering rate for specular tunneling as pancakes become disordered along the c-axis at higher H, leading to a plateau at moderate H.

C-axis tunneling in Bi2Sr2CaCu2O8+δ in the magnetic field up to 60 T

Abstract We report on the c -axis resistivity ϱ c ( H ) in Bi 2 Sr 2 CaCu 2 O 8+δ that exhibits a maximum in quasi-static magnetic fields up to 60 T. We show that below T c c -axis tunneling is a parallel, two-channel process: (i) σ j of Cooper pairs and (ii) σ q of quasiparticles: σ c = σ j + σ q . We demonstrate that high-field c -armaxis conductivity is linear-in-field at H H c 2 , in agreement with the field-linear dependence of quasiparticle conductivity σ q we find in mesas. Near 60 T, as temperature decreases, ϱ c saturates, confirming a gapless spectrum of quasiparticles. The linear ϱ c ( 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.

ANGULAR DEPENDENCE OF C-AXIS MAGNETORESISTANCE IN BI2SR2CACU2O8+DELTA SINGLE CRYSTALS WITH COLUMNAR DEFECTS

We measured the angular dependence of the c-axis magnetoresistance rho_c(B) of Bi-2212 irradiated with heavy ions. At temperatures near 68 K the scaling of rho_c(B) with the c-axis magnetic field component B_perp is broken and the in-plane field, B_parallel, affects rho_c. At this temperature, at a specific field B_cr \approx B_Phi/2, magnetoresistance becomes independent of field orientation. This crossing point allows us to estimate the correlation length L of pancake positions along the c axis. We find L/s is about 100 at B=B_cr, where s is the interlayer spacing. This provides evidence of strong enhancement of pancake alignment in the vortex liquid in crystals with columnar defects.

Structure of Vortex Liquid Phase in Irradiated Bi{sub 2} Sr{sub 2} CaCu{sub 2} O{sub 8{minus}{delta} } Crystals

The c-axis resistivity in irradiated and in pristine BSCCO(2212) crystals is measured as a function of the in-plane magnetic field component at fixed out-of-plane component B_\perp in the vortex liquid phase at T=67 K. From this data we extract the dependence of the phase difference correlation length inside layers on B_\perp and estimate the average length of pieces of vortex lines confined inside columnar defects as a function of the filling factor f=B_\perp / B_\phi. The maximum length, about 15 interlayer distances, is reached near f=0.35.

Angular dependence of {ital c}-axis magnetoresistance in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} single crystals with columnar defects

We measured the angular dependence of the c-axis magnetoresistance rho_c(B) of Bi-2212 irradiated with heavy ions. At temperatures near 68 K the scaling of rho_c(B) with the c-axis magnetic field component B_perp is broken and the in-plane field, B_parallel, affects rho_c. At this temperature, at a specific field B_cr \approx B_Phi/2, magnetoresistance becomes independent of field orientation. This crossing point allows us to estimate the correlation length L of pancake positions along the c axis. We find L/s is about 100 at B=B_cr, where s is the interlayer spacing. This provides evidence of strong enhancement of pancake alignment in the vortex liquid in crystals with columnar defects.

Structure of vortex liquid phase in irradiated BSCCO(2212) crystals

The c-axis resistivity in irradiated and in pristine BSCCO(2212) crystals is measured as a function of the in-plane magnetic field component at fixed out-of-plane component B_\perp in the vortex liquid phase at T=67 K. From this data we extract the dependence of the phase difference correlation length inside layers on B_\perp and estimate the average length of pieces of vortex lines confined inside columnar defects as a function of the filling factor f=B_\perp / B_\phi. The maximum length, about 15 interlayer distances, is reached near f=0.35.

Angular Dependence of C-Axis Magnetoresistance in Bi-2212 Single Crystals With Columnar Defects

We measured the angular dependence of the c-axis magnetoresistance rho_c(B) of Bi-2212 irradiated with heavy ions. At temperatures near 68 K the scaling of rho_c(B) with the c-axis magnetic field component B_perp is broken and the in-plane field, B_parallel, affects rho_c. At this temperature, at a specific field B_cr \approx B_Phi/2, magnetoresistance becomes independent of field orientation. This crossing point allows us to estimate the correlation length L of pancake positions along the c axis. We find L/s is about 100 at B=B_cr, where s is the interlayer spacing. This provides evidence of strong enhancement of pancake alignment in the vortex liquid in crystals with columnar defects.