Imaging the real space structure of the spin fluctuations in an iron-based superconductor.

Spin fluctuations are a leading candidate for the pairing mechanism in high temperature superconductors, supported by the common appearance of a distinct resonance in the spin susceptibility across the cuprates, iron-based superconductors and many heavy fermion materials. The information we have about the spin resonance comes almost exclusively from neutron scattering. Here we demonstrate that by using low-temperature scanning tunnelling microscopy and spectroscopy we can characterize the spin resonance in real space.

Reorientation of the diagonal double-stripe spin structure at FeTe bulk and thin-film surfaces.

Establishing the relation between ubiquitous antiferromagnetism in the parent compounds of unconventional superconductors and their superconducting phase is important for understanding the complex physics in these materials. Going from bulk systems to thin films additionally affects their phase diagram. For FeTe, the parent compound of FeSeTe superconductors, bulk-sensitive neutron diffraction revealed an in-plane oriented diagonal double-stripe antiferromagnetic spin structure.

Structural and electronic properties of ultrathin FeSe films grown on BiSe(0 0 0 1) studied by STM/STS.

We report scanning tunnelling microscopy and spectroscopy (STM/STS) studies on one and two unit cell (UC) high FeSe thin films grown on BiSe(0 0 0 1). In our thin films, we find the tetragonal phase of FeSe and dumb-bell shaped defects oriented along Se-Se bond directions. In addition, we observe striped moiré patterns with a periodicity of (7.

Evidence for orbital order and its relation to superconductivity in FeSe0.4Te0.6.

The emergence of nematic electronic states accompanied by a structural phase transition is a recurring theme in many correlated electron materials, including the high-temperature copper oxide- and iron-based superconductors. We provide evidence for nematic electronic states in the iron-chalcogenide superconductor FeSe0.4Te0.

Magnetic microscopy. Real-space imaging of the atomic-scale magnetic structure of Fe(1+y)Te.

Spin-polarized scanning tunneling microscopy (SP-STM) has been used extensively to study magnetic properties of nanostructures. Using SP-STM to visualize magnetic order in strongly correlated materials on an atomic scale is highly desirable, but challenging. We achieved this goal in iron tellurium (Fe(1+ y)Te), the nonsuperconducting parent compound of the iron chalcogenides, by using a STM tip with a magnetic cluster at its apex.

Polaronic pseudogap in the metallic phase of La(0.625)Ca(0.375)MnO(3) thin films.

The electronic density of states (DOS) of La(0.625)Ca(0.375)MnO(3) (LCMO) strain-free epitaxial thin films with an insulator-metal transition temperature (T(IM)) of 250 K was probed using variable-temperature scanning tunneling microscopy and spectroscopy.