Dr. Charlie Steiner (PhD University of Illinois at Urbana-Champaign, currently at CEEALAR)

Two-dimensional and quasi-two-dimensional systems host some of the most interesting behavior of electrons, including high-temperature superconductivity. One outstanding probe of electronic structure that coincidentally works best at measuring two-dimensional things is scanning tunneling microscopy (STM). STM measures the amplitude of the electron wavefunction at a surface by measuring the tunneling current to an atomically sharp conductive probe. To prepare films as thin as a single molecule, we grow our samples with molecular beam epitaxy (MBE) and then carefully transfer them in vacuum to the STM. Here we want to present results about the electronic structure of two films, tin diselenide ( SnSe₂ ) and iron selenide - or more accurately, iron selenide alloyed with iron telluride ( Fe(Se_xTe_1-x) ). Tin diselenide is a relatively mundane detective story, where we believe the culprit is Moiré pattern physics. Fe(Se,Te) is an iron-based superconductor and a topological insulator, and we find evidence of unusual orbital correlations in the normal state.

Fig. caption: STM image of FeSe surface

STM image of FeSe surface