Fermi surface and superconducting gap of FeTe$_{1-x}$Se$_{x}$ superconductor studied by high-resolution ARPES

The origin of superconductivity in FeTe$_{1-x}$Se$_{x}$ superconductor is a subject of intensive debate, since the parent compound FeTe shows considerably different electronic and magnetic properties compared to FeAs-based families. To clarify the superconducting mechanism, an experimental investigation of the low-energy electronic structure is of particular importance. Here, we report our recent high-resolution ARPES results on FeTe$_{1-x}$Se$_{x}$ superconductor, and demonstrate several universalities in the electronic states between FeTe$_{1-x}$Se$_{x}$ and FeAs-based superconductors.