arXiv subjects

S. Urayama

Publications and source records attributed to S. Urayama.

3 recordsLinked to original sources

arXiv2006

Periodic oscillations of flux flow resistance in intrinsic Josephson junctions with various lateral sizes down to a size of non-linear core of Josephson vortex

To investigate in-phase structures (rectangular lattice) of Josephson vortex lattice (JVL) in intrinsic Josephson junctions (IJJs) of Bi2Sr2CaCu2O8+d, we fabricated IJJs with various lateral sizes down to a size of non-linear core of Josephson vortex using focused-ion-beam etching and measured flux flow resistance (RFF) with in-plane magnetic fields (H). We have found that above a size-independent critical field, the critical current shows Fraunhofer pattern in narrow-length IJJs (0.29-2.77 mm), and then the RFF~H oscillates with H0 period. Most strikingly, such oscillations become pulse-like in sub-micron IJJs, indicating that between the pulses, the rectangular JVLs become major structures.

cond-mat.supr-con↗

arXiv2006

Periodic Oscillations of Josephson-Vortex Flow Resistance in Oxygen-Deficient Y1Ba2Cu3Ox

We measured the Josephson vortex flow resistance as a function of magnetic field applied parallel to the ab-planes using annealed Y1Ba2Cu3Ox intrinsic Josephson junctions having high anisotropy (around 40) by oxygen content reduction. Periodic oscillations were observed in magnetic fields above 45-58 kOe, corresponding to dense-dilute boundary for Josephson vortex lattice. The observed period of oscillations, agrees well with the increase of one fluxon per two junctions ($H_{p}$\textit{=$Φ$}$_{0}$\textit{/2Ls}), may correspond to formation of a triangular lattice of Josephson vortices as has been reported by Ooi et al. for highly anisotropic (larger than 200) Bi-2212 intrinsic Josephson junctions.

cond-mat.supr-con↗

arXiv2005

Fiske steps studied with flux-flow resistance oscillation in a narrow stack of Bi2Sr2CaCu2O8+d junctions

We have experimentally investigated the fluxon dynamics in a narrow Bi2Sr2CaCu2O8+d stack with junction length L~1.8 um. As an evidence of high-frequency excitation by a collective cavity mode, under an (in-plane) external magnetic field, the current-voltage characteristics show prominent Fiske steps with the corresponding resonance frequencies of 75-305 GHz. Further study of flux-flow resistance oscillation with various c-axis currents clarifies the correlation with Fiske steps by distinguishing two different regions i.e., static flux-flow region at low bias current level and dynamic Fiske step region at high bias current level.

cond-mat.supr-con↗