double quantum dot*

 

The scanning tip of an atomic force microscope was coupled to electrons confined in a gate-defined double quantum dot (DQD) fabricated on a Si/SiGe heterostructure. Even though the electrons in the accumulation-mode heterostructure are confined beneath the metallic gates, the lever arm of the tip is large enough to change the DQD charge occupation by moving the tip around or changing the tip bias voltage [1, 2]. We map resonance lines of the tip-interaction potential by measuring the currents through the DQD and a proximal charge sensor dot. By applying a microwave tone to the tip we are able to perform excited state spectroscopy via photon-assisted tunneling [3].

[1] Pioda et al., PRL 93, 216801 (2004)

[2] Fallahi et al., Nano Lett. 5, 223 (2004)

[3] Wang et al., PRL 111, 046801 (2013)