Low temperature magnetic penetration depth in d-wave superconductors

We briefly review the experimental results of the low temperature magnetic penetration depth λ(T) of d-wave superconductors. In very clean high-T_c superconductors (HTSC) the low temperature in-plane penetration depth λ_‖(T) varies linearly with T. A weaker power law temperature dependence is found for the out-of-plane penetration depth λ_⊥(T) in most of HTSC. In the organic superconductors κ-(BEDT-TTF)₂X [X=Cu(NCS)₂, Cu[N(CN)₂]Br] and slightly dirty HTSC λ_‖∝bT²/(T*+T), where is deduced from an impurity scattering model. In clean CeCoIn₅ a crossover from linear to quadratic temperature behavior at low T was interpreted as the first evidence for nonlocal effects in a d-wave superconductor.     

Ultra-sensitive bolometers for atomic hydrogen detection

Two different types of bolometers have been developed to be used for spin-polarized atomic hydrogen detection. One of them uses a thin Cu shell as the absorber and a doped Ge chip as the thermometer element. The other uses a silver film as the absorber and a superconductor-insulator-normal metal junction to measure the temperature rise of the electrons in the absorber. These bolometers have a calculated noise equivalent power of 10^–15 WHz^–1/2 and 10^–17 WHz^–1/2, respectively, and can detect down to 6 × 10³ and 800 particles, respectively, at an operating temperature of 100 mK. If these detectors perform as predicted, the minimum number of detectable hydrogen atoms will be improved by several orders of magnitude.     

Spin-polarized Hydrogen in a High Field Trap: Towards a Two-Component Bose Gas

We have loaded spin-polarized hydrogen (SPH) into a magnetostatic Ioffe trap with central fields as high as 1 T and at two different temperatures, 0.25 and 0.4 K, on the way to create a gas of SPH with two distinguishable Bose component. We have measured the magnetic dipole decay rate constant of SPH at these high fields and found good agreement with theory. A measurement technique that allows determination of the absolute number of atoms was developed.