Using both scanning tunneling microscopy (STM) and angle-resolved photo-electron spectroscopy (ARPES) gives researchers a more complete understanding of high-temperature superconducting materials. STM can show actual atoms on the material's surface. ARPES uses the photoelectric effect by aiming a beam of light (photons) at the material's surface. The photons excite atoms in the material, causing them to eject electrons, which are then captured by a detector. The momentum (speed and direction) of the ejected electrons gives researchers information about the momentum of the electrons inside the material.

Credit: Nicolle Rager Fuller, National Science Foundation