H. Rosner

The quantum nature of skyrmions and half-skyrmions in Cu2OSeO3

The Skyrme-particle, the skyrmion, was introduced over half a century ago in the context of dense nuclear matter. But with skyrmions being mathematical objects--special types of topological solitons--they can emerge in much broader contexts. Recently skyrmions were observed in helimagnets, forming nanoscale spin-textures. Extending over length scales much larger than the interatomic spacing, they behave as large, classical objects, yet deep inside they are of quantum nature. Penetrating into their microscopic roots requires a multi-scale approach, spanning the full quantum to classical domain. Here, we achieve this for the first time in the skyrmionic Mott insulator Cu2OSeO3. We show that its magnetic building blocks are strongly fluctuating Cu4 tetrahedra, spawning a continuum theory that culminates in 51 nm large skyrmions, in striking agreement with experiment. One of the further predictions that ensues is the temperature-dependent decay of skyrmions into half-skyrmions.

Prediction of High Tc Superconductivity in Hole-Doped LiBC

The layered lithium borocarbide LiBC, isovalent with and structurally similar to the superconductor MgB2, is an insulator due to the modulation within the hexagonal layers (BC vs B2). We show that hole doping of LiBC results in Fermi surfaces of B-C p sigma character that couple very strongly to B-C bond stretching modes, precisely the features that lead to superconductivity at T(c) approximately equal to 40 K in MgB2. Comparison of Li(0.5)BC with MgB2 indicates the former to be a prime candidate for electron-phonon coupled superconductivity at substantially higher temperature than in MgB2.

Magnetic and structural transitions in layered iron arsenide systems: AFe2As2 versus RFeAsO

Resistivity, specific-heat, and magnetic-susceptibility measurements performed on

Superconducting state in SrFe2-xCoxAs2 by internal doping of the iron arsenide layers.

{\text{SrFe}}_{2}{\text{As}}_{2}

Evidence for a reentrant superconducting state in EuFe2AS2 under pressure

samples evidence a behavior very similar to that observed in LaFeAsO and

Strong coupling between magnetic and structural order parameters in SrFe2As2

{\text{BaFe}}_{2}{\text{As}}_{2}

AFe2As2 (A = Ca, Sr, Ba, Eu) and SrFe2-xTMxAs2 (TM = Mn, Co, Ni): crystal structure, charge doping, magnetism and superconductivity

, with the difference being that the formation of the spin-density wave and the lattice deformation occur in a pronounced first-order transition at

Superconductivity in the Platinum Germanides MPt4Ge12 (M = Rare-Earth or Alkaline-Earth Metal) with Filled Skutterudite Structure

{T}_{0}=205\text{ }\text{K}

Application of spark plasma sintering to the fabrication of binary and ternary skutterudites

. Comparing further data evidences that the Fe magnetism is stronger in

Heat and charge transport properties of MgB2

{\text{SrFe}}_{2}{\text{As}}_{2}