Title: Imaging Unconventional Superconducting Order with STM via Particle-Hole Interference

 

Abstract: It remains challenging to experimentally determine the symmetry and topology of order parameters in unconventional superconductors. While scanning tunneling microscopy (STM) offers atomic-scale spatial resolution, conventional quasiparticle interference near a single impurity is largely insensitive to the complex phase structure of the superconducting gap. 

 

In this talk, I will present a theoretical proposal for a new STM-based experiment that uses particle-hole interference of Bogoliubov quasiparticles near a pair of impurities to image superconducting order parameters. I will show how under controlled rotation of impurities, the changes in the impurity-induced interference patterns can be studied to infer angular structure, nodal directions, and phase winding of the superconducting gap function. I will discuss how the effect can be applied to distinguish between several theoretically proposed order parameter candidates in the unconventional superconductor Strontium Ruthenate. 

 

I will then discuss a boundary-assisted realization, in which a single impurity interferes with its mirror-reflected "ghost" image near a step edge or domain boundary. This geometry produces the same interference physics at first order in the impurity potential, making the effect substantially stronger and more experimentally accessible. Together, these results establish particle-hole interference as a theoretical blueprint for a new STM probe of unconventional and topological superconductivity. 

 

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