Low-temperature superconductivity is warming up.
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Biomedical subjects
Paul C Canfield
Publications and source records attributed to Paul C Canfield.
A new look at bonding in trialuminides: reinvestigation of TaAl3.
Single crystals of TaAl3 were grown at high temperatures from an Al-rich, binary solution. TaAl3 adopts the D0(22) structure type, space group I4/mmm with a=3.8412(5) A, c=8.5402(17) A, and Z=2. The structure type, which is the preferred structure for all group 5 trialuminides and TiAl3 as well as the high-temperature form of HfAl3, is a binary coloring of the face-centered-cubic (fcc) arrangement. The distribution of Ta atoms creates a three-dimensional network of vertex and edge-sharing square pyramids of Al atoms. Temperature-dependent electrical resistivity and magnetic susceptibility measurements are consistent with TaAl3 being a metallic compound with a relatively low density of states at the Fermi surface. Furthermore, tight-binding electronic structure calculations are utilized to describe the bonding in these compounds and to compare their stability with respect to the alternative fcc-related, e.g., the D0(23) (ZrAl3-type) and the L1(2) (AuCu3-type), structures. A modified Wade's rule argument provides insights into the structural preferences.
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Hexagonal and square flux line lattices in CeCoIn5.
Using small-angle neutron scattering, we have imaged the magnetic flux line lattice (FLL) in the d-wave heavy-fermion superconductor CeCoIn5. At low fields we find a hexagonal FLL. Around 0.6 T this undergoes what is most likely a first-order transition to square symmetry, with the nearest neighbors oriented along the gap node directions. This orientation of the square FLL is consistent with theoretical predictions based on the d-wave order parameter symmetry.
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