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O: Fachverband Oberflächenphysik

O 5: Scanning Probe Microscopy: Light-Matter Interactions at the Atomic Scale I

O 5.6: Talk

Monday, March 17, 2025, 11:45–12:00, H6

Ultrafast Coulomb blockade in an atomic-scale quantum dot — Jonas Allerbeck¹, •Laric Bobzien¹, Nils Krane¹, S. Eve Ammerman¹, Daniel E. Cintron Figueroa², Joshua Robinson^2,3, and Bruno Schuler¹ — ¹Empa - nanotech@surfaces Laboratory, 8600 Dübendorf, Switzerland — ²Department of Chemistry, The Pennsylvania State University, University Park, 16802, PA, USA — ³Department of Physics and Department of Materials Science and Engineering, The Pennsylvania State University, University Park, 16802, PA, USA.

Controlling electron dynamics at optical clock rates is a fundamental challenge in lightwave-driven nanoelectronics. At the example of individual selenium vacancies (Vac_Se) in few-layer tungsten diselenide (WSe₂), which are prototypical atomic-scale quantum dots with localized defect states, I present ultrafast charge transfer in the time domain using lightwave-driven scanning tunneling microscopy (LW-STM). Layer-dependent decoupling of Vac_Se in WSe₂ varies the average charge-state lifetime of defect states from 1.2 ps (1L) to 3 ns (4L), showing an unexpected sub-exponential. Picosecond terahertz (THz) source pulses, focused onto the picocavity of the STM, control and read the charge state of individual Vac_Se quantum dots. THz pump-THz probe time-domain sampling of the defect charge population captures atomic-scale snapshots of the transient Coulomb blockade, a signature of charge transport via quantized defect states. These results open new avenues for exploring charge dynamics and lightwave-driven electronics at the space-time limit.

Keywords: ultrafast scanning probe microscopy; THz-STM; field-driven tunneling; atomic defects; 2D semiconductors