https://doi.org/10.1140/epjb/e2009-00143-2
Projection operator approach to transport in complex single-particle quantum systems
1
Fachbereich Physik, Universität Osnabrück, Barbarastrasse 7, 49069 Osnabrück, Germany
2
Physikalisches Institut, Universität Freiburg, Hermann-Herder-Strasse 3, 79104 Freiburg, Germany
3
Hanse-Wissenschaftskolleg, Institute for Advanced Study, 27753 Delmenhorst, Germany
Corresponding author: a rsteinig@uos.de
Received:
9
January
2009
Revised:
27
March
2009
Published online:
25
April
2009
We discuss the time-convolutionless (TCL) projection operator approach to transport in closed quantum systems. The projection onto local densities of quantities such as energy, magnetization, particle number, etc. yields the reduced dynamics of the respective quantities in terms of a systematic perturbation expansion. In particular, the lowest order contribution of this expansion is used as a strategy for the analysis of transport in “modular” quantum systems corresponding to quasi one-dimensional structures which consist of identical or similar many-level subunits. Such modular quantum systems are demonstrated to represent many physical situations and several examples of complex single-particle models are analyzed in detail. For these quantum systems lowest order TCL is shown to represent an efficient tool which also allows to investigate the dependence of transport on the considered length scale. To estimate the range of validity of the obtained equations of motion we extend the standard projection to include additional degrees of freedom which model non-Markovian effects of higher orders.
PACS: 05.60.Gg – Quantum transport / 05.30.-d – Quantum statistical mechanics / 05.70.Ln – Nonequilibrium and irreversible thermodynamics
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2009