Oliver E. Buckley Condensed Matter Physics Prize: Scanned Josephson and Andreev Tunneling Microscopy: Visualizing Electron-Pair Fluids and Density Waves

Superconductors are quantum fluids and pair density waves (PDW) are quantum crystals. Both are macroscopic quantum states of coherently condensed electron pairs. To visualize and explore these states directly at atomic scale, scanned Josephson tunneling microscopes^1-5 (SJTM) are now used. Such instruments can image both the single-electron quasiparticles and, in a different mode, the quantum condensate of electron-pairs. Moreover, these instruments can, in the Andreev quasiparticle retroreflection regime, be operated as scanned Andreev tunneling microscopes (SATM). Emerging research areas include:  visualization of PDW states in conventional spin-singlet superconductors¹; in cuprate d-wave  high-temperature superconductors using d-wave scan tips^2,3,4; and in putative spin-triplet topological superconductors⁵.  PDW studies using SJTM and SATM thus open a rich new vein of macroscopic quantum physics, with great potential for discovery.

 

References

[1] Science 372, 1447 (2021)

[2] Nature 532, 343 (2016)

[3] Science 364, 976 (2019)

[4] Nature 580, 6570 (2020)

[5] Nature (2023) arXiv:2209.10859