The Physics & Astronomy Colloquium Series presents Ilija Zeljkovic of Boston College, discussing STM - at the cutting edge: "Nanoscale Imaging of Unusual Density Waves in Kagome Superconductors" on Nov. 17.

Absract : The kagome lattice of transition metal atoms provides an exciting platform to study the interplay of electronic correlations and band topology. Recently discovered kagome superconductors A V ₃ Sb ₅  ( A =K, Rb, Cs) set off an avalanche of theoretical and experimental work for unusual superconductivity and charge density waves believed to be connected with exotic orbital loop currents.

In this talk, I will present our experiments on A V ₃ Sb ₅  where we uncovered a cascade of symmetry-broken electronic states emerging as a function of temperature. Using variable-temperature spectroscopic imaging scanning tunneling microscopy, we imaged a series of density waves, with different morphologies and dimensionality, all co-existing with superconductivity. We observe distinct signatures of spontaneous rotation symmetry breaking in the electronic structure, demonstrating the tendency of this family of materials towards electronic unidirectionality. Our experiments reveal a complex landscape of electronic states that can co-exist on a kagome lattice, and provide intriguing parallels to high- T _c  superconductors and twisted bilayer graphene.