Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 12: Nanostructures at Surfaces I

O 12.1: Talk

Monday, March 17, 2025, 15:00–15:15, H6

Imaging standing phonons within topological defect in strong coupling superconductor by scanning tunneling microscopy — •Qili Li, Thomas Gozlinski, Rolf Heid, Jörg Schmalian, and Wulf Wulfhekel — Karlsruhe Institute of Technology, Karlsruhe, Germany

Electron-phonon coupling plays an important role in conventional superconductors. Understanding the behavior of phonons will promote the applications of conventional superconductors. However, it is difficult to observe the spatial behavior of phonons. Here, we utilize inelastic scanning tunneling microscopy (ISTS) at 45 mK to investigate phonons within topological defect, i.e. stacking fault tetrahedron (SFT), in the strong coupling superconductor Pb(111) [1]. We find that the local Eliashberg function [2,3] is significantly enhanced by SFTs. Moreover, lateral standing waves of phonon are also observed on SFTs. Compared with phonon bandstructure, we find that the SFTs have strong confinement on transverse acoustic phonons, while the longitudinal acoustic phonons are less confined. Our findings pave the way to phonon engineering in strong coupling superconductors. [1] PRL 14, 108 (1965). [2] Sov. Phys. JETP 11, 696 (1960). [3] PRL 114, 047002 (2015).

Keywords: Phonons; Topological defects; Strong coupling superconductor; Scanning tunneling microscopy