Co-doping of lanthanum and phosphorus in CaFe2As2 induces superconductivity at 45 K. This superconducting transition temperature is higher than the 38 K transition in Ba1−xKxFe2As2, which is the maximum found thus far among the 122 phases. Superconductivity with a substantial shielding volume fraction was observed at 0.12 ≤ x ≤ 0.18 and y = 0.06 in Ca1−xLaxFe2(As1−yPy)2. The superconducting phase of the present system seems to be not adjacent to an antiferromagnetic phase.

No abstract

We report the unprecedented square-planar coordination of iridium in the iron iridium arsenide Ca 10 (Ir 4 As 8 )(Fe 2 As 2 ) 5 . This material experiences superconductivity at 16 K. X-ray photoemission spectroscopy and first-principles band calculation suggest Ir(II) oxidation state, which yields electrically conductive Ir 4 As 8 layers. Such metallic spacer layers are thought to enhance the interlayer coupling of Fe 2 As 2 , in which superconductivity emerges, thus offering a way to control the superconducting transition temperature.

Mineral calaverite AuTe 2 is a layered compound with an incommensurately modulated structure. The modulation is characterized by the formation of molecular-like Te 2 dimers. We have found that the breaking of Te 2 dimers that occurs in Au 1Àx Pt x Te 2 results in the emergence of superconductivity at T c ¼ 4:0 K.KEYWORDS: superconductivity, dimer breaking, telluride, CdI 2 typeThe breaking and making of chemical bonds are essential for designing materials. Hoffmann and Zheng developed a theory of bond manipulation in ThCr 2 Si 2 -type AT 2 X 2 (A = alkali, alkali-earth, or rare-earth element, T = transition element, X = group 14 or 15 element). 1) AT 2 X 2 is formed by stacking covalently bonded T 2 X 2 layers composed of edge-sharing TX 4 tetrahedra, and ionic A atoms. Interlayer X-X covalent bonds can be tuned by filling the d band in T elements.

The effects of phosphorus doping on the structural and superconducting phase transitions of BaNi2(As(1-x)P(x))2 were studied. The specific heat, resistivity, and magnetic susceptibility were measured. The results revealed an abrupt increase in the superconducting transition temperature (T(c)) from 0.6 K in the triclinic phase (space group P1¯) with less phosphorus (x≤0.067) to 3.3 K in the tetragonal phase (space group I4/mmm) with more phosphorus (x≥0.067). Our data analysis suggests that a doping-induced softening related to an in-plane Ni and As(P) phonon mode is responsible for the enhanced superconductivity in the tetragonal phase.