Colloquium: Read-out of Phosphorus Donor Spin States
Tue Oct 14 12:00pm - 1:00pm
Location: Hercus Theatre, University of Melbourne
Presented by Professor Martin Brandt, Walter Schottky Institut, Technische Universität München, Germany
Via electronic transport measurements, paramagnetic centers such as defects can be detected very sensitively in semiconductor devices. We have recently demonstrated that also the actual spin state can be determined via time-resolved spin-dependent transport measurements. These experiments rely on the Pauli principle, which governs the transitions of electrons between paramagnetic states. As the detection system, we use the capture of on electron from a Phosphorus donor by a Si/SiO2-interface state. Since the final state is doubly occupied, the Pauli principle demands that state to be a spin singlet. Only Phosphorus/interface state pairs in the same singlet state can undergo the capture process while pairs in a triplet state cannot, providing the selection rule required for our experiments.
In pulsed electrically detected magnetic resonance (pEDMR), we can make use of this selection rule in a variety of ways which will be discussed in the talk. Most importantly, we can perform experiments as a function of the microwave pulse duration, and observe Rabi flops which allow to determine the spin state of either partner. Furthermore, using a double resonance scheme, we can show that the Phosphorus/interface state pairs constitute the dominant spin-dependent recombination process. The double resonance technique also allows the quantitative determination of the singlet recombination time. Finally, using so-called echo tomography, we can observe spin echos in the electronic transport, and use those to further study the kinetics of the spin-dependent transition as well as to determine spin-spin coupling strengths. In an outlook, the talk will address how this spin-readout scheme could be used in the context of quantum information processing.
This work was supported by Deutsche Forschungsgemeinschaft through Sonderforschungsbereich 631 "Solid-State Quantum Information Processing: Physical Concepts and Materials Aspects".