Probing a single acceptor in a silicon nanotransistor

We have demonstrated single hole transport through a silicon nano-transistor using an individual boron atom. Holes bound to acceptor atoms in silicon experience a much stronger spin-orbit interaction than electrons bound to donor atoms. This makes them interesting candidates for electric-field controllable qubits. The energy spectrum of the observed single boron atom in the transistor is 4-fold degenerate, which is expected for acceptor atoms in bulk silicon. This offers a unique two-level system of a heavy and light hole state in an already gated structure. The effect of the nanostructure is observed in a change of Landé g-factor compared to ensembles of boron atoms in bulk silicon.