Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 16: Superconductivity: Properties and Electronic Structure II

TT 16.4: Talk

Tuesday, March 18, 2025, 10:15–10:30, H32

Observation of saddle point nesting driven charge order on the surface of a 122-type iron-based superconductors — •Yu Zheng — Tsung Dao Lee Institute, Shanghai Jiao Tong University, 1 Lisuo Road, Shanghai, 201210

Unconventional superconductivity is known for intertwining with other correlated states, making the exploration for new intertwined orders highly important for understanding the mechanism of unconventional superconductivity. Spin and nematic orders are widely observed in the iron-based superconductors (FeSCs). However, evidence for charge order in the phase diagrams of FeSCs is rarely found. Employing STM and DFT, here we demonstrate,through expanding the phase diagram of Ba_1−xK_xFe₂As₂ to the heavily hole doped regime by surface doping, the formation of a CDW order on the As-terminated surface of Ba_0.23K_0.77Fe₂As₂, whose emergence suppresses superconductivity completely, indicating direct competition between the two. Notably, the wavevector of the charge order matches with the nesting vector between the near-EF saddle points, suggesting saddle-point nesting as its driving mechanism.

Keywords: charge density wave; scanning tunneling microsopy