Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session X7: Computational Nonequilibrium Many-body Physics: From Classical to Quantum Simulation |
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Sponsoring Units: DCOMP Chair: David Langreth, Rutgers University Room: Colorado Convention Center Korbel 4A-4B |
Friday, March 9, 2007 8:00AM - 8:36AM |
X7.00001: Short-time dynamics of correlated quantum Coulomb systems Invited Speaker: Strong correlations in dense Coulomb systems are attracting increasing interest in many fields ranging from dense astrophysical plasmas, dusty plasmas and semiconductors to metal clusters and ultracold trapped ions [1]. Examples are bound states in dense plasmas (atoms, molecules, clusters) and semiconductors (excitons, trions, biexcitons) and many-particle correlations such as Coulomb and Yukawa liquids and crystals. Of particular current interest is the response of these systems to short excitations generated e.g. by femtosecond laser pulses and giving rise to ultrafast relaxation processes and build up of binary correlations. The proper theoretical tool are non-Markovian quantum kinetic equations [1,2] which can be derived from Nonequilibrium Green's Functions (NEGF) and are now successfully solved numerically for dense plasmas and semiconductors [3], correlated electrons [4] and other many-body systems with moderate correlations [5]. This method is well suited to compute the nonlinear response to strong fields selfconsistently including many-body effects [6]. Finally, we discuss recent extensions of the NEGF-computations to the dynamics of strongly correlated Coulomb systems, such as single atoms and molecules [7] and electron and exciton Wigner crystals in quantum dots [8,9]. \newline \newline [1] H. Haug and A.-P. Jauho, {\em Quantum Kinetics in Transport and Optics of Semiconductors}, Springer 1996; M. Bonitz {\em Quantum Kinetic Theory}, Teubner, Stuttgart/Leipzig 1998; \newline [2] {\em Progress in Nonequilibrium Green's Functions III}, M. Bonitz and A. Filinov (Eds.), J. Phys. Conf. Ser. vol. 35 (2006); \newline [3] M. Bonitz et al. Journal of Physics: Condensed Matter {\bf 8}, 6057 (1996); R. Binder, H.S. K\"ohler, and M. Bonitz, Phys. Rev. B 55, 5110 (1997); \newline [4] N.H. Kwong, and M.~Bonitz, Phys. Rev. Lett. {\bf 84}, 1768 (2000); \newline [5] {\em Introduction to Computational Methods for Many-Body Systems}, M. Bonitz and D. Semkat (eds.), Rinton Press, Princeton (2006); \newline [6] H. Haberland, M. Bonitz, and D. Kremp, Phys. Rev. E {\bf 64}, 026405 (2001); \newline [7] N.E. Dahlen, A. Stan and R. van Leeuwen, p. 324 in Ref. 2.; \newline [8] A. Filinov, M. Bonitz, and Yu. Lozovik, Phys. Rev. Lett. {\bf 86}, 3851 (2001); \newline [9] K. Balzer, N.E. Dahlen, R. van Leeuwen, and M. Bonitz, to be published [Preview Abstract] |
Friday, March 9, 2007 8:36AM - 9:12AM |
X7.00002: Simulation of the Interaction of Intense Laser Pulses with Dense Plasma Invited Speaker: For some time now the interaction of intense laser beams with dense plasma has generated interest not only because of its relevance for the Fast Ignition concept in the field of Inertial Confinement Fusion (ICF) [1], but also due to the many fundamental physics problems related to it like laser energy deposition in plasma, the transport of the deposited energy via fast electrons or the propagation of ultra-high electric currents through plasma and many more. Of great interest at present are the details of the deposition and the transport of the energy of intense laser pulses in plasma. Of great importance in this context are collisions and collective effects. The proper equations are a set of classical relativistic Maxwell-Vlasov-Boltzmann equations. They are solved numerically with a Monte-Carlo Particle-In-Cell (MCPIC) [2] approach in three spatial dimensions. This quasi-particle method is capable of calculating effects as diverse as the degree of laser absorption in plasma, the generation of fast electrons, the relaxation of laser-generated non-Maxwellian electron and ion distribution functions due to collective effects and binary collisions, the propagation of electron driven heat waves into the plasma, or the generation of vast quasi-steady electric and magnetic fields. Details of the MCPIC-method applicable to systems of intense laser radiation interacting with plasma are presented. The application of the method to the acceleration of protons with intense lasers featuring collisional transport of fast electrons through solid density plasma and the excitation of teravolt electric fields is demonstrated [3]. \newline \newline [1] M. Tabak, J. Hammer, M. E. Glinski, W. L. Kruer, S. C. Wilks, and R. J. Mason, ``Ignition and high gain with ultrapowerful lasers,'' Phys. PLasmas \textbf{1}, 1626 (1994). \newline [2] ``Introduction to Computational Methods for Many-Body Systems,'' M. Bonitz and D. Semkat (eds.), Rinton Press, Princeton (2006) \newline [3] B. M. Hegelich, B. J. Albright, J. Cobble, K. Flippo, S. Letzring, M. Paffett, H. Ruhl, J. Schreiber, R. K. Schulze and J. C. Fern\'andez, ``Laser acceleration of quasi-monoenergetic MeV ion beams,'' Nature \textbf{439}, 441 (2006). [Preview Abstract] |
Friday, March 9, 2007 9:12AM - 9:48AM |
X7.00003: Nonequilibrium dynamical mean-field theory Invited Speaker: Dynamical mean-field theory (DMFT) is establishing itself as one of the most powerful approaches to the quantum many-body problem in strongly correlated electron materials. Recently, the formalism has been generalized to study nonequilibrium problems [1,2], such as the evolution of Bloch oscillations in a material that changes from a diffusive metal to a Mott insulator [2,3]. Using a real-time formalism on the Kadanoff-Baym-Keldysh contour, the DMFT algorithm can be generalized to the case of systems that are not time-translation invariant. The computational algorithm has a parallel implementation with essentially a linear scale up when running on thousands of processors. Results on the decay of Bloch oscillations, their change of character within the Mott insulator, and movies on how electrons redistribute themselves due to their response to an external electrical field will be presented. In addition to solid-state applications, this work also applies to the behavior of mixtures of light and heavy cold atoms in optical lattices. \newline \newline [1] V. M. Turkowski and J. K. Freericks, Spectral moment sum rules for strongly correlated electrons in time-dependent electric fields, Phys. Rev. B {\bf } 075108 (2006); Erratum, Phys. Rev. B {\bf 73}, 209902(E) (2006). \newline [2] J. K. Freericks, V. M. Turkowski , and V. Zlati\'c, Nonlinear response of strongly correlated materials to large electric fields, in {\it Proceedings of the HPCMP Users Group Conference 2006, Denver, CO, June 26--29, 2006} edited by D. E. Post (IEEE Computer Society, Los Alamitos, CA, 2006), to appear. \newline [3] J. K. Freericks, V. M. Turkowski, and V. Zlati\'c, Nonequilibrium dynamical mean-field theory, {\it submitted to Phys. Rev. Lett.} cond-mat//0607053. [Preview Abstract] |
Friday, March 9, 2007 9:48AM - 10:24AM |
X7.00004: Signal transport and finite bias conductance in and through correlated nanostructures Invited Speaker: The problem of calculating the finite bias conductance through an interacting system has been formally solved by Meir and Wingreen using non-equilibrium Green function techniques [1]. In practice, the evaluation of these formulas for interacting systems is generally based on approximative schemes. Time dependent density matrix renormalization group methods (t-DMRG) [2] allow for an exact solution of the time-dependent evolution of many-body wavefunctions. We apply this technique to the problem of calculating the differential conductance of a strongly correlated nanostructure attached to one-dimensional noninteracting leads. By carefully monitoring the finite-size effects and the time-dependent dynamics, the differential conductance can be extracted from the t-DMRG results [3]. This talk will give an introduction to t-DMRG and its application to the calculation of transport properties. We present examples of signal propagation through interacting systems and how the linear and differential conductance varies for interacting systems tuned from weak to strong coupling. Refs: [1] Y. Meir and N. S. Wingreen, Phys. Rev. Lett. 68, 2512 (1992). [2] K. A. Hallberg, Adv. Phys. 55,, 477 (2006) and references therein. [3] G. Schneider and P. Schmitteckert, Conductance in strongly correlated 1D systems: Real-Time Dynamics in DMRG, condmat/0601389. [Preview Abstract] |
Friday, March 9, 2007 10:24AM - 11:00AM |
X7.00005: Calculations of molecular electronics with the DFT/NEGF method Invited Speaker: |
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