Research

1. Materials Computation Center, University of Illinois Duane D. Johnson and Richard Martin, NSF DMR-03-25939Spintronics in Quantum Dots J.P. Leburton (ECE) and R.M. Martin (Physics) Research Objectives: Understand many-body effects in semiconductor quantum dots (QDs) for applications in quantum information processing. Approach: We concentrate on material and design parameters that influence the exchange interaction between conduction electrons in realistic double QDs. For this purpose, we use a combined approach based on density functional theory (DFT) to model the QD potential, and diffusion quantum Monte Carlo to simulate accurately exchange and correlation of electrons in the QD. Significant Results: We investigate quantum structures designed for three linearly coupled vertical QDs made by lithography techniques (artificial “molecules” in analogy with CO2 or NH2 linear molecules). DFT calculations show the design of gates is critical for electron confinement and could result in more than three dots depending of the surface covered by metal gates. Broader Impact: Controlled device design through science, and cross-disciplinary trained students for industry. Left: STM image of three linearly coupled QDs device. Right: Contour plot of the first 8 wave functions in a double dot. Localization is shown in the first four states in the center of the structure, while the fifth and sixth are localized at structure’s edge indicating presence of two other dots. R. Ravishankar. P. Matagne, J.P. Leburton, R.M Martin and S. Tarucha, Phys. Rev. B 69,035326 (2004)