A Spin Interference Device

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A Spin Interference DeviceAbstract Spintronics is an emerging area in solid state science and engineering. Its broad goal is to utilize carriers' spin in metals and semiconductors to realize novel electronic devices. In such devices, of key importance are the creation, manipulation, and detection of spin and spin-currents. An example is the spin-FET (field-effect transistor), a switching device whose operation is based on the injection of spin-polarized carriers into the channel, manipulation (rotation via precession) of their spin via an external electric field (gate bias), and the spin-sensitive detection of the carriers at the drain. If successful, such manipulation of spins can also have impact on another emerging, and perhaps even more exotic, field of quantum computing, as spin is the leading candidate for the quantum bit of information in the proposed quantum computers. The goal of this project is demonstrate the realization of a spin device which is somewhat similar to the spin-FET but has the simplifying advantage that it does not require the injection or detection of spin-polarized carriers. The device is essentially an Aharanov-Bohm ring made of a two-dimensional (2D) carrier system with a strong and tunable spin-orbit interaction. Its operation relies on the interference between the clockwise and counter-clockwise travelling spin wave functions. The interference, and therefore the conductance of the ring, can be modulated by a gate electrode which tunes the spin-orbit interaction. The project combines state-of-the art nanotechnology and careful transport measurements. It also requires a high-quality 2D carrier system with tunable spin-orbit interaction. The 2D holes in modulation-doped GaAs/AlGaAs heterostructures provide a nearly ideal system for this project; they have very high low-temperature mobility, of the order of 106 cm2/Vs, and the tunability of their spin-orbit interaction has recently been demonstrated.