Serafim Teknowijoyo

Nodeless multiband superconductivity in stoichiometric single-crystalline CaKFe4As4

Measurements of the London penetration depth Δλ(T) and tunneling conductance in single crystals of the recently discovered stoichiometric iron-based superconductor CaKFe4As4 (CaK1144) show nodeless, two-effective-gap superconductivity with a larger gap of about 6–10 meV and a smaller gap of about 1–4 meV. Having a critical temperature Tc,onset ≈ 35.8 K, this material behaves similar to slightly overdoped (Ba1–xKx)Fe2As2 (e.g., x = 0.54,Tc ≈ 34 K), a known multigap s± superconductor. Here, we conclude that the superconducting behavior of stoichiometric CaK1144 demonstrates that two-gap s± superconductivity is an essential property of high-temperature superconductivity in iron-based superconductors, independent of the degree of substitutional disorder.

Enhancement of superconducting transition temperature by pointlike disorder and anisotropic energy gap in FeSe single crystals

S. Teknowijoyo, K. Cho, M. A. Tanatar, J. Gonzales, A. E. Böhmer, O. Cavani, V. Mishra, 4 P. J. Hirschfeld, S. L. Bud’ko, P. C. Canfield, and R. Prozorov ∗ Ames Laboratory and Department of Physics & Astronomy, Iowa State University, Ames, IA 50011, USA Laboratoire des Solides Irradís, École Polytechnique, CNRS, CEA, Universit Paris-Saclay, 91128 Palaiseau Cedex, France Joint Institute of Computational Sciences, University of Tennessee, Knoxville, TN-37996, USA Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN-37831, USA Department of Physics, University of Florida, Gainesville, Florida 32611, USA (Dated: 13 May 2016)

Complex superconductivity in the noncentrosymmetric compound Re6Zr

We report the electronic structure, synthesis, and measurements of the magnetic, transport, and thermal properties of the polycrystalline noncentrosymmetric compound Re

Comparative Study of the Effects of Electron Irradiation and Natural Disorder in Single Crystals of SrFe2(As1-xPx)2 Superconductor (x=0.35)

_{6}

Using electron irradiation to probe iron-based superconductors

Zr. We observed a bulk superconducting transition at temperature

Dependence of the absolute value of the penetration depth in (Ba1–xKx)Fe2As2 on doping

T_{c}

Comparative study of the effects of electron irradiation and natural disorder in single crystals of SrFe

\sim

_{2}

6.7 K, and measured the resistivity, heat capacity, thermal conductivity, and the London penetration depth below the transition, as well as performed doping and pressure studies. From these measurements we extracted the critical field, and the superconducting parameters of Re

(As

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