arXiv subjects

S. M. Kim

Publications and source records attributed to S. M. Kim.

5 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↗

arXiv1995

Multiple Gluon Effects in $q+\bar q\to t+\bar t + X$ at FNAL Energies: Semi-Analytical Results

We apply our Yennie-Frautschi-Suura exponentiated cross section formulas for the parton processes $q + {^(} \bar q {^)}{^\prime} \ra q{^\prime}{^\prime} + {^(} \bar q {^)}{^\prime}{^\prime}{^\prime} + n(G)$ to the process $q + \bar q \ra t + \bar t + n(G)$ at FNAL energies, where G is a QCD gluon. We use semi-analytical methods to compute the ratio $r_{exp}=σ_{exp}/σ_B$, where $σ_{exp}$ is our soft gluon YFS exponentiated cross section and $σ_B$ is the Born cross section. For $m_t= 0.176(0.199)$TeV, we get $r_{exp}=1.65(1.48)$, respectively, for $q=u$ for example. These results are not inconsistent with the recent observations by CDF and D0.

hep-ph↗

arXiv1993

Flavor Dependence of Sea Quark Structure Functions

Quark masses are shown to play an important role in the nucleon sea. Our analysis using massive QCD splitting functions demonstrates the existence of two Feynman-$x$ sea regimes. For small $x$ the strange sea is larger while at large $x$ the non-strange light sea is dominant. This crossover effect has been observed in a phenomenological analysis by the CTEQ Collaboration. We also investigate the charm component in the nucleon.

hep-ph↗