5 research outputs found
Magnetic penetration depth in electron-doped cuprates - evidence for gap nodes
The in-plane penetration depth \lambda(T) is measured in electron-doped
single crystals Nd1.85Ce0.15CuO4-x (NCCO) and Pr1.85Ce0.15CuO4-x (PCCO) using a
11 MHz LC resonator. In NCCO, \lambda(T) exhibits a minimum at 3.8 K and a
pronounced upturn down to 0.4 K due to the paramagnetic contribution of Nd3+
ions. The London penetration depth contribution is linear in T. The
paramagnetic contribution is absent in PCCO, where \lambda(T)~T^2 at low
temperatures. Our results indicate the presence of nodes in the superconducting
gap, i.e., non s-wave symmetry of the order parameter in electron-doped
cuprates.Comment: 2 pages Acrobat-3 optimized PDF. To be presented at M2S-HTSC-V
Topological Hysteresis in the Intermediate State of Type-I Superconductors
Magneto-optical imaging of thick stress-free lead samples reveals two
distinct topologies of the intermediate state. Flux tubes are formed upon
magnetic field penetration (closed topology) and laminar patterns appear upon
flux exit (open topology). Two-dimensional distributions of shielding currents
were obtained by applying an efficient inversion scheme. Quantitative analysis
of the magnetic induction distribution and correlation with magnetization
measurements indicate that observed topological differences between the two
phases are responsible for experimentally observable magnetic hysteresis.Comment: 4 pages, RevTex
Anisotropic s-wave superconductivity in single crystals CaAlSi from penetration depth measurements
In- and out-of-plane London penetration depths were measured in single
crystals CaAlSi (T_{c}=6.2 K and 7.3 K) using a tunnel-diode resonator. A full
3D BCS analysis of the superfluid density is consistent with a prolate
spheroidal gap, with a weak-coupling BCS value in the ab-plane and stronger
coupling along the c-axis. The gap anisotropy was found to significantly
decrease for higher T_{c} samples.Comment: 4 page
Magnetic Penetration Depth in Unconventional Superconductors
This topical review summarizes various features of magnetic penetration depth
in unconventional superconductors. Precise measurements of the penetration
depth as a function of temperature, magnetic field and crystal orientation can
provide detailed information about the pairing state. Examples are given of
unconventional pairing in hole- and electron-doped cuprates, organic and heavy
fermion superconductors. The ability to apply an external magnetic field adds a
new dimension to penetration depth measurements. We discuss how field dependent
measurements can be used to study surface Andreev bound states, nonlinear
Meissner effects, magnetic impurities, magnetic ordering, proximity effects and
vortex motion. We also discuss how penetration depth measurements as a function
of orientation can be used to explore superconductors with more than one gap
and with anisotropic gaps. Details relevant to the analysis of penetration
depth data in anisotropic samples are also discussed.Comment: topical review, 57 pages, 219 reference