Charge and Spin Transport in Nanostructures
L. L. Bonilla (Universidad Carlos III de Madrid, Spain) and M. Carretero (Universidad Carlos III de Madrid, Spain)
Electronic transport is the basis of many nanotechnology applications. Spin transport and spintronics are used to create better computer memories, basic science and many interesting applications are being actively pursued. In this minisymposium, different models of quantum charge and spin transport in low-dimensional nanostructures will be discussed.
Romano derives quantum hydrodynamic equations from kinetic equations by using the maximum entropy principle to close the hierarchy of moment equations. Barletti discusses superlattices (SL) with Rashba spin-orbit effects. A semiconductor SL is an artificial one-dimensional crystal. In materials with spin-orbit effects, electrons with different spin have different energies and can transport spin. Barletti presents a simple quantum kinetic equation for the SL. Using singular perturbations he derives spatially nonlocal equations for electric field and electron populations, and solves them to show that this SL may behave as a spin oscillator. A different spin oscillator can be achieved by applying a static magnetic field to a weakly coupled SL if at least one period contains magnetic impurities. Carretero analyzes a spatially discrete model of this system demonstrating its behavior as an injector of spin polarized time-periodic current. Platero discusses the use of double quantum dots as spin-current rectifiers. Quantum dots (QD) are artificial atoms, two QD separated by a barrier (double quantum dots, DQD) are artificial molecules. Attaching contacts to a DQD, electrons with a precise value of spin can tunnel through the barrier from one QD if there is an available state in the other dot and appropriate voltage bias is held between the contacts. Otherwise the Pauli principle precludes tunneling (spin-Coulomb blockade). Thus the DQD acts as a nanoscale spin rectifier, blocking current in one bias direction and allowing it in the other. Platero analyzes a simple transport model for this system and compares it to available experiments.
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