Abstract
We propose a measurement scheme to directly detect odd-frequency superconductivity via time- and angle-resolved photoelectron fluctuation spectroscopy. The scheme includes two consecutive, non-overlapping probe pulses applied to a superconducting sample. The photoemitted electrons are collected in a momentum-resolved fashion. Correlations between signals with opposite momenta are analyzed. Remarkably, these correlations are directly proportional to the absolute square of the time-ordered anomalous Green's function of the superconductor. This setup allows for the direct detection of the "hidden order parameter" of odd-frequency pairing. We illustrate this general scheme by analyzing the signal for the prototypical case of a two-band superconductor.
Highlights
Odd-frequency superconductivity is a genuinely dynamic state of matter
In Eqs. (6) and (7) and the related discussion in the main text, we present the above equation
In this Appendix, we present the way we perform the Fourier transformation of the anomalous Green’s functions, even and odd, for a model of a two-band superconductor described in Ref. [25]
Summary
Odd-frequency superconductivity is a genuinely dynamic state of matter. It is based on a pairing mechanism in which the two electrons that form a Cooper pair in the superconducting condensate have to correlate with each other at unequal times. Recent theoretical proposals to detect odd-frequency pairing are, for instance, based on measurements of a supercurrent running from a Majorana scanning tunneling microscope tip to a superconducting substrate [18], transport properties through a quantum spin Hall system in proximity to a s-wave superconductor [19], the Josephson current on the surface of Weyl nodal loop semimetals [20], or the Josephson junction current noise [21]. This feature is the mathematical working principle behind our detection scheme, which is physically based on time- and angle-resolved photoelectron fluctuation spectroscopy
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