Conserving approximations for correlated inhomogeneous systems; from molecules to quantum transport
DIPC Seminars
- Speaker
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Adrian Stan, École Polytechnique, Saclay, France
- When
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2013/11/19
13:00 - Place
- Donostia International Physics Center (DIPC). Paseo Manuel de Lardizabal, 4 (nearby the Facultad de Quimica), Donostia
- Add to calendar
-
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**Conserving approximations for correlated inhomogeneous systems; from
molecules to quantum transport
**
Adrian Stan
Laboratoire des Solides Irradi_x0013_es, Ecole Polytechnique, Palaiseau, France, and
European Theoretical Spectroscopy Facility (ETSF)
Abstract
The study of electron dynamics and energy transfer fi nds its natural
framework in the nonequilibrium Green function method. A relatively simple
object – depending on only two coordinates G(x,t;x0,t0) – the Green
function contains a wealth of information: electron density and current, total
energy, or excitation energies. When conserving self-energy approximations are
used to calculate it, i.e., Hartree-Fock, Second Born, GW or T-matrix, the
resulting observables satisfy the underlying conservation laws.
I will start by introducing a unifying framework to solve the Dyson and the
Kadanoff -Baym equations within four di fferent conserving approximations.
Before moving forward, I will explore the di fferent levels of self-
consistency, in the case of the GW approximation, and investigate their e
ffects on total energies, ionization potentials, and particle number. Drawing
on the unifi ed formalism, I will move the many-body approach in the time
domain to study the short-time dynamics of correlated electrons in isolated
molecules and systems connected to metallic leads. This approach fully
accounts for electron correlations in the presence of time-dependent external
fields, and extends the Meir-Wingreen formula to the time domain.
Incorporating many-body e ffects beyond Hartree-Fock leads to a bias-dependent
gap closing, quasiparticle broadening, shortening of the transient times and
smoothening of the steps in the current-voltage curves. Aside from these
immediate e ffects, I will discuss the possibility of fi nding multistability
in the density and current of an interacting nanoscale junction coupled to
semi-in finite leads. These results are compared with the counterpart
observables calculated from time-dependent density functional theory (TDDFT)
and the exact method of time-dependent density matrix renormalization group
(tDMRG).
Host at DIPC: Peter Koval 8770