Cooper pair spectroscopy (COPS)
High temperature superconductivity in copper-oxide based superconductors (cuprates) as well as other high temperature superconductors are central topics in contemporary physics. At the heart of superconductivity lie the pairs of electrons, Cooper pairs, that are formed and condense into a superconducting condensate below a critical temperature Tc. Here a novel technique, based on the photoemission of both electrons in a Cooper pair by a single photon, is proposed as a tool to directly study these pairs and superconductivity. Cooper-pair spectroscopy was theorized 20 years ago but has never been experimentally demonstrated and even deemed unachievable. Through numerical simulations we have shown that using the latest advances in light source technology and electron detection techniques together with software filtering based on the unique properties of Cooper pairs, Cooper-pair spectroscopy can become a reality. Cooper-pair spectroscopy would allow for the direct detection of the building blocks of superconductivity and would thus unequivocally demonstrate the presence of such pairs even in the absence of phase coherence, which is necessary for hall mark effects such as zero resistance or the Meissner effect. Cooper-pair spectroscopy would thus be able to confirm or rule out the existence of pairs above Tc in high-temperature superconductors or in the so called pseudogap phase. Cooper-pair spectroscopy will permit the measurement of the momentum of Cooper pairs thus allowing for the test of various theories for the superconducting and pseudogap phases of high-temperature superconductivity. Furthermore, Cooper-pair spectroscopy has unique properties that could also be used to determine the gap function as well as the phase transition between various paired states. Cooper-pair spectroscopy will open a new window into the world of superconductivity.
We gratefully acknowledge financial support for this project from the Knut and Alice Wallenberg foundation, the Olle Engkvist foundation and the Carl Trygger foundation.
