Direct evidence of pairing up to pseudogap energy in cuprate high-temperature superconductors: part I

In the cuprate high-temperature superconductors, the pseudogap phase connects the Mott insulator and superconductivity phases. Despite extensive research, the origin of the pseudogap remains elusive. A key question, debated for decades, is whether the pseudogap is associated with electron pairing, or if it corresponds to a local ordered state. Shot noise experiments, which can directly detect electron pairing, have the potential to resolve this long-standing debate. First, I will present data from mesoscopic junctions, which demonstrate that shot noise does not generally detect pairing [1], and I will explain why our shot noise microscope is a better choice [2]. I will then present how our new shot noise microscope allows us to detect pairing in a d-wave superconductor [3].

[1] J. Niu et al. Why shot noise does not generally detect pairing in mesoscopic superconducting tunnel junctions, Phys. Rev. Lett. 132, 076001 (2024).
[2] K. Bastianns et. al., Amplifier for scanning tunneling microscopy at MHz frequencies, Rev. Sci. Instrum. 89, 093709 (2018)
[3] J. Niu* & M. Ortego Larrazabal* et. al., Equivalence of pseudogap and pairing energy in a cuprate high-temperature superconductor, arXiv:2409.15928.