Control of inter-dot electrostatic coupling by a side gate in a silicon double quantum dot operating at 4.5 K

We report on electron transport measurements of a lithographically-defined silicon double quantum dot (DQD) coupled in series with a top gate and side gates. The structure of the top gate coupled uniformly to the DQD is suitable for realizing a few-electron regime. The obtained small DQD enables us to observe a clear honeycomb-like charge stability diagram at a temperature of 4.5 K. The validity of the DQD structure is confirmed by theoretical calculations. Furthermore, we demonstrate successful modulation of the inter-dot electrostatic coupling by the side gate. Externally tunable coupling is essential for practical implementation of spin-based quantum information devices.