Comparative analysis of tunneling magnetoresistance in low-$T_c$ Nb/AlAlOx/Nb and high-$T_c$ Bi${}_{2-y}$Pb${}_y$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$ intrinsic Josephson junctions

Abstract

We perform a detailed comparison of magnetotunneling in conventional low-$T_c$ Nb/AlAlOx/Nb junctions with that in slightly overdoped Bi${}_{2-y}$Pb${}_y$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$ [Bi(Pb)-2212] intrinsic Josephson junctions and with microscopic calculations. It is found that both types of junctions behave in a qualitatively similar way. Both magnetic field and temperature suppress superconductivity in the state-conserving manner. This leads to the characteristic sign-change of tunneling magnetoresistance from the negative at the sub-gap to the positive at the sum-gap bias. We derived theoretically and verified experimentally scaling laws of magnetotunneling characteristics and employ them for accurate extraction of the upper critical field $H_{c2}$. For Nb an extended region of surface superconductivity at $H_{c2}<H<H_{c3}$ is observed. The parameters of Bi(Pb)-2212 were obtained from self-consistent analysis of magnetotunneling data at different levels of bias, dissipation powers and for different mesa sizes, which precludes the influence of self-heating. It is found that $H_{c2}(0)$ for Bi(Pb)-2212 is $\simeq 70$ T and decreases significantly at $T\to T_c$. The amplitude of sub-gap magnetoresistance is suppressed exponentially at $T>T_c/2$, but remains negative, although very small, above $T_c$. This may indicate existence of an extended fluctuation region, which, however, does not destroy the general second-order type of the phase transition at $T_c$.

14 pages, 8 figures

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• Switching current distributions and subgap structures of underdoped (Hg,Re)Ba2Ca2Cu3O8+d intrinsic Josephson junctions
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• Disparity of superconducting and pseudogap scales in low-Tc Bi-2201 cuprates
• Temperature dependence of geometrical and velocity matching resonances in Bi2Sr2CaCu2O8+x intrinsic Josephson junctions
• Influence of the Fermi surface geometry on a Josephson effect between an iron-pnictide and conventional superconductors
• Low anisotropy of the upper critical field in a strongly anisotropic layered cuprate: Evidence for paramagnetically limited superconductivity
• Persistent electrical doping of Bi2Sr2CaCu2O8+x mesa structures
• Superconducting condensate residing on small Fermi pockets in underdoped cuprates
• Comment on Counterintuitive consequence of heating in strongly driven intrinsic junctions of Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$ mesas
• Observation of a subharmonic gap singularity in interlayer tunneling characteristics of Bi2Sr2CaCu2O8+d
• Strong polaritonic interaction between flux-flow and phonon resonances in Bi2Sr2CaCu2O8+x intrinsic Josephson junctions: Angular dependence and the alignment procedure
• Quantization of the superconducting energy gap in an intense microwave field