Vibration-assisted tunneling through single Au adatoms on two-dimensional WSe2

Abstract

Scanning tunneling microscopy (STM) at 5 K was used to study individual Au atoms adsorbed on the surface of a WSe2 layer grown on epitaxial graphene. In line with theoretical predictions, scanning tunneling spectroscopy measurements reveal that the weakly bound adatom gives rise to an electronic state within the energy band gap of the WSe2 layer. Adatoms in different surface locations show different gap-state energy values that follow a random distribution around the Fermi level of the sample with a standard deviation of ~50 meV. The location-dependent shift is attributed to spatial variations in disorder potential. Tunneling via the gap state is accompanied by vibrational excitations as apparent from pronounced sideband peaks in the conductance spectra with Poisson-distributed intensities indicating significant electron-phonon coupling with a Huang-Rhys factor of S=2.8. STM tunneling through single Au adatoms on two-dimensional WSe2 constitutes a model case of resonant double-barrier tunneling accompanied by strong coupling to vibrational degrees of freedom.

Main text: 19 pages plus 7 figures; Supplemental Material: 3 pages plus 2 figures

References in corpus (6)

• Weak antilocalization in epitaxial graphene: evidence for chiral electrons
• Franck-Condon blockade in suspended carbon nanotube quantum dots
• Vibrational sidebands and dissipative tunneling in molecular transistors
• Engineering and probing atomic quantum defects in 2D semiconductors: A perspective
• Moiré tuning of spin excitations: Individual Fe atoms on MoS${}_2$/Au(111)
• Tuning a two-impurity Kondo system by a moiré superstructure