SKM 2023 – scientific programme

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O: Fachverband Oberflächenphysik

O 97: Focus Session: Scanning Probe Microscopy with Quartz Sensors IV

O 97.6: Talk

Friday, March 31, 2023, 12:00–12:15, TRE Ma

Revelation of an inhomogeneous broadening effect in artificial quantum structures caused by electron-adsorbate scattering — •Marco Weiß, Fabian Stilp, and Franz Giessibl — Institute of Experimental and Applied Physics, University of Regensburg, Universitätsstraße 31, 93053 Regensburg

In 1993 Crommie et al. [1] arranged 48 Fe adatoms on a Cu(111) surface in a circle with a diameter of 14.26 nm. This quantum corral confines surface electrons in a circular potential well. Past investigations with scanning tunneling microscopy revealed energetically discrete eigenstates with radial Bessel functions. These studies on the Fe quantum corral showed unwanted movement of the corral walls during spectroscopic measurements because of the weak bonding of Fe on Cu(111) [1].

We used CO molecules to provide the corral with more stable walls. This permitted us to access a larger voltage window and allowed for a detailed line shape analysis of the corrals eigenenergy levels. Surprisingly, we discovered a dominant Gaussian broadening of the eigenstates.

We find that the spectral width is dependent on the size of the quantum structure. The introduction of a simple model linking the energy dependence of this inhomogeneous broadening with the single particle movement of surface state electrons has shown that the observed behaviour is compatible with an electronic lifetime limitation by interaction with the corral wall.

[1] M. F. Crommie et al., Science 262, 218-220 (1993).