arXiv subjects

N. Kameda

Publications and source records attributed to N. Kameda.

3 recordsLinked to original sources

arXiv2004

Josephson Plasma Resonance in $Bi_2 Sr_2 Ca Cu_2 O_{8+y}$ with Spatially Dependent Interlayer-Phase Coherence

We study the Josephson plasma resonance (JPR) in Bi$_2$Sr$_2$CaCu$_2$O$_{8+y}$ (BSCCO) with spatially dependent interlayer-phase coherence (IPC). The half-irradiated BSCCO (HI-BSCCO), in which columnar defects are introduced only in a half of the sample, shows several resonance peaks, which are not simple superposition of the peaks in irradiated- and pristine-parts. JPR in HI-BSCCO changes its character from irradiated- to pristine-type at a crossover frequency ($ω_{cr}$). We demonstrate that the one-dimensional \LSGE, which takes into account the spatial dependence of IPC, can reproduce most of the experimental findings including the presence of $ω_{cr}$.

cond-mat.supr-con↗

arXiv2002

Campbell Penetration Depth of a Superconductor in the Critical State

The magnetic penetration depth $λ(T,H,j)$ was measured in the presence of a slowly relaxing supercurrent, $j$. In single crystal $\mathrm{Bi_2Sr_2CaCu_2O_8}$ below approximately 25 K, $λ(T,H,j)$ is strongly hysteretic. We propose that the irreversibility arises from a shift of the vortex position within its pinning well as $j$ changes. The Campbell length depends upon the ratio $j/j_{c}$ where $j_{c}$ is the critical current defined through the Labusch parameter. Similar effects were observed in other cuprates and in an organic superconductor.

cond-mat.supr-con↗

arXiv2000

Evidence for Surface Andreev Bound states in Cuprate Superconductors from Penetration Depth Measurements

Tunneling and theoretical studies have suggested that Andreev bound states form at certain surfaces of unconventional superconductors. Through studies of the temperature and field dependence of the in-plane magnetic penetration depth lambda_ab at low temperature, we have found strong evidence for the presence of these states in clean single crystal YBCO and BSCCO. Crystals cut to expose a [110] interface show a strong upturn in lambda_ab at around 7K, when the field is oriented so that the supercurrents flow around this surface. In YBCO this upturn is completely suppressed by a field of ~0.1 T.

cond-mat.supr-con↗