Thomas Dittrich

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We present a comprehensive account of directed transport in one-dimensional Hamiltonian systems with spatial and temporal periodicity. They can be considered as Hamiltonian ratchets in the sense that ensembles of particles can show directed ballistic transport in the absence of an average force. We discuss general conditions for such directed transport like(More)
The influence of periodic driving on coherent tunneling is investigated, using a quartic double-well potential in a monochromatic external field as a working example. Extensive numerical studies of the long-time behaviour of this system are combined with an analytical description on basis of the quasienergy formalism. Approximate solutions of the dynamics(More)
The electron diffusion coefficient at varying porosity has been determined in a series of nanostructured TiO(2) films of different initial thicknesses. The porosity was changed by applying different pressures prior to sintering, thereby modifying the internal morphology of the films though not their chemical and surface conditions. A systematic increase of(More)
We have investigated the electrostatic potential distribution in compact and nanoporous TiO2 films, deposited on conducting F-doped SnO2 substrate (FTO), which are used in dye-sensitized solar cells. The TiO2 films were immersed into aqueous electrolyte and excited from the FTO side by light pulses of a N2 laser while the current response was measured as a(More)
We make use of the numerical simulation random walk (RWNS) method to compute the "jump" diffusion coefficient of electrons in nanostructured materials via mean-square displacement. First, a summary of analytical results is given that relates the diffusion coefficient obtained from RWNS to those in the multiple-trapping (MT) and hopping models. Simulations(More)
Using the parametrically driven harmonic oscillator as a working example, we study two different Markov-ian approaches to the quantum dynamics of a periodically driven system with dissipation. In the simpler approach, the driving enters the master equation for the reduced density operator only in the Hamiltonian term. An improved master equation is achieved(More)
The hydrophilic drug ampicillin (AP) was comprehensively studied in vitro with focus on an ion pair approach of AP. The influence of the counter ions in comparison with AP derivatives was studied on the water solubility, lipid partition, and transport across artificial lipid membranes as well as using an in vitro absorption model system. It was found that(More)
Non-rechargeable batteries with a life of 20 years and more are required today for many smart metering and AMR applications in the US. Tadiran's non-rechargeable lithium thionyl chloride batteries offer a proven life of 25 years. Kohler's new touchless commercial faucet was designed to run even 30 years on a hybrid lithium battery. Similar requirements(More)
Chaotic tunneling in a driven double-well system is investigated in absence as well as in the presence of dissipation. As the constitutive mechanism of chaos-assisted tunneling, we focus on the dynamics in the vicinity of three-level crossings in the quasienergy spectrum. They are formed when a tunnel doublet, located on a pair of symmetry-related tori in(More)
Here we report the preparation of high performance Quantum Dot Sensitized Solar Cells (QDSCs) based on PbS-CdS co-sensitized nanoporous TiO2 electrodes. QDs were directly grown on the TiO2 mesostructure by the Successive Ionic Layer Absorption and Reaction (SILAR) technique. This method is characterized by a fast deposition rate which involves random(More)