A two-atom electron pump : non-adiabatic regime and Landau-Zener-Stückelberg interferences
Shrinking down the dimensions of field-effect transistors has opened opportunities to probe transport through a single donor atom in silicon nanostructures [1, 2]. We demonstrate the next degree of complexity in donor-based electronics, namely a system of two coupled donors. Our ultrasmall 3-gate silicon nanostructures allow controlling independently the energy levels of two phosphorus or arsenic donors, in series between source and drain electrodes. This device was recently used to measure the separation between the two first states of a donor . Beyond this
new spectroscopy technique, this coupled atom transistor provides unprecedented functionalities since we are able to manipulate a single electron over two donor states. In this talk I will present electron pumping through two donors in series . We investigate both the adiabatic and non-adiabatic regimes by changing the driving frequency. While quantized pumping is achieved in the low frequency adiabatic regime, we observe remarkable features at higher frequency when the charge transfer is limited by the different tunneling rates. We reproduce in details the characteristic signatures observed in the non-adiabatic regime by using a master equation, including the tunnel couplings. The transitions between quantum states are modeled with a Landau-Zener transition. Driving such a system at higher frequency, above 3 GHz, the coherence of the coupling between the two dopants is revealed. Indeed multiple Landau-Zener events interfere with each other and the so-called Landau-Zener-Stückelberg interference pattern is obtained .
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