Strongly Correlated Nonequilibrium Transport Simulation in Complex Quantum Dot and Bulk Systems

TECHNICAL SUMMARY This award supports computational and theoretical research and education on quantum nonequilibrium effects in mesoscopic and nanosystems. Based on the PI?s recent imaginary-time formulation of steady-state nonequilibrium transport, complex quantum dot systems will be studied via quantum Monte Carlo technique and other numerical many-body tools through the Matsubara voltage method. The PI will apply this formalism to nonlinear transport problems of complex quantum models which are currently difficult to study through computation. Recent experiments on several molecular junctions show a Kondo zero-bias anomaly accompanied by conductance oscillations at the source-drain bias comparable to the Kondo energy scale. The oscillation has been speculated to be from molecular vibrations. The PI will pursue an Anderson-Holstein model to investigate the roles of non-Jahn-Teller and Jahn-Teller electron-phonon coupling, and the on-site Coulomb interaction. The PI will study strong correlation effects in spin-injection proposed for spintronics devices. The nonequilibrium theory will be extended to the bulk limit using two different implementations of the dynamical mean-field theory: effect of multiple-chemical potentials in Fermi lattice and electric field driven transport of charged particles using the Bloch oscillation basis. The PI is actively involved in interdisciplinary research with the Electric Engineering and Mechanical Engineering Departments, and also in outreach effort of artistic representation of physics ideas in collaboration with the department of visual studies. NONTECHNICAL SUMMARY This award supports theoretical research and education to study mesoscopic systems and nanostructures, such as large molecules or interconnected systems of large molecules, that are out of balance with their surroundings due to, for example, the application of an electric field, and for which quantum mechanics dominates. This research builds on methods developed by the PI that will enable him to calculate how well these structures conduct electricity and to explore new phenomena. Motivated by experiments, the PI will apply his approach to determine how strong interactions among electrons, and electrons and phonons affect the transport of electrons through the structures. This research contributes to the broad fundamental understanding of the phenomena that arise in the world around us. Conventional theories used to develop semiconductor devices become increasingly inadequate to describe devices now approaching the size molecules where the notion of a device and material become increasingly blurred. This effort contributes to the intellectual foundations for future technologies that would utilize molecules and nanoscale structures to construct electronic devices as a strategy to sustain the tremendous growth of the electronics industry encapsulated in ?Moore?s Law.? This research project contributes to the general understanding of quantum mechanical nonequilibrium behavior of mesoscale and nanoscale structures coupled to open systems. The general problem of how quantum information is transported and lost through coupling to the environment has impact on the emerging area of quantum computing. The PI is actively involved in interdisciplinary research with the Electric Engineering and Mechanical Engineering Departments, and also in outreach effort of artistic representation of physics ideas in collaboration with the department of visual studies.