Quantum devices: engineering electronic coherence in nanostructures

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Our group builds and measures nanoscale electronic devices whose geometries are designed to yield new physics from a transport (resistance) measurement. Our experiments are performed at low temperature--typically less than 1 Kelvin--where electronic properties are dominated by coherent quantum mechanical effects. In this limit, signals sent from laboratory equipment to the device under test provide in situ control over quantum mechanical degrees of freedom. We propose a three-pronged approach to our research in the coming 5 years. The first builds off of our most successful set of experiments from the past 5 years; the second continues our group's expansion into one of the hottest new fields in condensed matter physics; the third takes advantage of our group's unique position to move into a new direction with great potential payoff: 1. We recently discovered a new phenomenon called ballistic spin resonance, in which spin-orbit interaction couples to geometric resonances to give fast spin rotations in a semiconductor (GaAs) device. Until now these spin rotations were detected only by a fast effective spin relaxation rate, but here we propose to exploit this this phenomenon for fast and tunable spin rotations as well. 2. Despite widespread predictions for long spin coherence times in single atomic layers of carbon known as graphene, very little is known from an experimental point of view about the behaviour of electron and hole spins in a practical sample. Our group made inroads into this area, demonstrating the first interference-based spin current measurement in graphene. We will greatly expand this area of research, applying our existing expertise in GaAs spin measurements to study spin coherence in graphene. 3. Groups around the world are only within the last year recognizing the influence that surface atoms can have on graphene's electronic properties. Here we propose to dramatically change graphene's properties in an intentional way by depositing particular atoms into and onto the graphene.