Qisheng Lin

Enhancement of the Superconducting Gap by Nesting in CaKFe4As4: A New High Temperature Superconductor

We use high resolution angle resolved photoemission spectroscopy and density functional theory with measured crystal structure parameters to study the electronic properties of CaKFe_{4}As_{4}. In contrast to the related CaFe_{2}As_{2} compounds, CaKFe_{4}As_{4} has a high T_{c} of 35xa0K at stochiometric composition. This presents a unique opportunity to study the properties of high temperature superconductivity in the iron arsenides in the absence of doping or substitution. The Fermi surface consists of several hole and electron pockets that have a range of diameters. We find that the values of the superconducting gap are nearly isotropic (within the explored portions of the Brillouin zone), but are significantly different for each of the Fermi surface (FS) sheets. Most importantly, we find that the momentum dependence of the gap magnitude plotted across the entire Brillouin zone displays a strong deviation from the simple cos(k_{x})cos(k_{y}) functional form of the gap function, proposed by the scenario of Cooper pairing driven by a short range antiferromagnetic exchange interaction. Instead, the maximum value of the gap is observed on FS sheets that are closest to the ideal nesting condition, in contrast to previous observations in other ferropnictides. These results provide strong support for the multiband character of superconductivity in CaKFe_{4}As_{4}, in which Cooper pairing forms on the electron and the hole bands interacting via a dominant interband repulsive interaction, enhanced by band nesting.

Tuning icosahedral quasicrystals and their approximants from the Mg2Zn11 structure

Electronic tuning of Sc−Mg−Zn icosahedral quasicrystal (i-QC) and approximant (AC) phases was achieved according to pseudogap predictions from an electronic band structure analysis of Mg2Zn11. The i-QC and two AC phases were obtained in the Mg2- x Sc x Zn11 system. The QC compositions are Sc10.8(6)Mg3.2(6)Zn86.0(2) and Sc14.6(4)Mg3.3(4)Zn82.1(2) by EDX for xu2009=u20091.0 and 1.5, respectively. X-ray structure determination reveals that the 1/1 AC, Sc3Mg0.18(1)Zn17.73(1), crystallizes in space group Im , with au2009=u200913.863(2)u2009Å. Electronic structure calculations on the 1/1 AC reveal that the Fermi level is located in the centre of the pseudogap, which appears to be greatly enhanced by Zn 4p and Sc 3d orbital mixing.

Ce3-xMgxCo9: Transformation of a Pauli Paramagnet into a Strong Permanent Magnet

We report on the synthesis of single crystalline and polycrystalline samples of Ce

Physical Properties of Single Crystalline R Mg 2 Cu 9 ( R = Y , Ce − Nd , Gd − Dy , Yb ) and the Search for In-Plane Magnetic Anisotropy in Hexagonal Systems

_{3-x}

Superconductivity versus structural phase transition in the closely related Bi2Rh3.5S2 and Bi2Rh3S2

Mg

Electron-Poor Polar Intermetallics: Complex Structures, Novel Clusters, and Intriguing Bonding with Pronounced Electron Delocalization

_x

Growth and characterization of BaZnGa

Co

Superconducting properties ofRh9In4S4single crystals

_9

Superconducting properties of Rh

solid solution (

_{9}

0leq x lesssim 1.4