Directional heat flow has been used as a probe of the symmetry of a carefully modified barium iron arsenide, superconductor, revealing features that have eluded other experimental methods. Superconductivity occurs because electrons form pairs that are trapped by an energy gap (or gaps) that the electrons cannot occupy. Depending on the direction in which an electron pair is moving, these gaps can be large, small, or even not exist at all.
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We report a femtosecond midinfrared study of the broadband low-energy response of individually separated (6,5) and (7,5) single-walled carbon nanotubes. Strong photoinduced absorption is observed around 200 meV, whose transition energy, oscillator strength, resonant chirality enhancement, and dynamics manifest the observation of quasi-one-dimensional intraexcitonic transitions. A model of the nanotube 1s-2p cross section agrees well with the signal amplitudes.
Fig. 1. Inelastic neutron scattering study of superconducting Ba(Fe0.926Co0.074)2As2 reveals anisotropic and quasi-two-dimensional magnetic fluctuations as well as novel quasi-propagating excitations at higher energies.
Fig. 1. Interface energy between a normal and superconducting region at the coexistence magnetic field as function of the ratio of the penetration and coherence length. Positive (negative) values imply Type I (II) superconductivity.
Scientists have discovered a way to make strong materials that are also ductile.