COPS · Cooper-pair spectroscopy: A new window into the world of superconductivity

High temperature superconductivity and other unconventional types of superconductivity, such as topological superconductivity, 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 superfluid state below a critical temperature Tc. An outstanding problem is the mechanism that underlies the electron-pairing in unconventional superconductors. Here this problem is addressed by developing a new experimental technique, based on the simultaneous photoemission of both electrons in a Cooper pair by a single photon. Cooper-pair spectroscopy was theorized 20 years ago but has so far never been achieved experimentally. Through numerical simulations it is shown, in this proposal, 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 will thus be able to confirm or rule out the existence of preformed pairs above Tc in high-temperature superconductors or in the so called pseudogap phase. Cooper-pair spectroscopy will also permit the measurement of the momentum of Cooper pairs thus allowing for the test of various theories for the superconducting and pseudogap phases of unconventional superconductors. Furthermore, Cooper-pair spectroscopy will allow for the characterization of topological superconductivity as well as the phase transition between topological and non-topological superconducting states. In short, Cooper-pair spectroscopy will open a new window into the world of superconductivity.