Conductance Distribution of a Quantum Dot with Non-Ideal Single-Channel Leads

We have computed the probability distribution of the conductance of a ballistic and chaotic cavity which is connected to two electron reservoirs by leads with a single propagating mode, for arbitrary values of the transmission probability Gamma of the mode, and for all three values of the symmetry index beta. The theory bridges the gap between previous work on ballistic leads (Gamma = 1) and on tunneling point contacts (Gamma << 1). We find that the beta-dependence of the distribution changes drastically in the crossover from the tunneling to the ballistic regime. This is relevant for experiments, which are usually in this crossover regime. ***Submitted to Physical Review B.***Comment: 7 pages, REVTeX-3.0, 4 postscript figures appended as self-extracting archive, INLO-PUB-940607

Concept for a resource-efficient process chain for hybrid bulk components with optimized energy utilization

A significant percentage of energy in hot forming is used to heat the components. Especially in manufacturing hybrid components, workpieces are heated in the preceding hot-joining process in addition to the heating cycles. Nevertheless, previous processing steps require longer times than the following hot forming processes leading to long downtimes. With the pre-production of workpieces, the machine's capacity is fully utilized but prevents the reuse of the residual heat. Consequently, an immense amount of energy is wasted due to additionally required heating cycles. Our approach is to develop a flexible and resource-efficient process chain. We combine two hot forming processes with different cycle times in a single process chain. Therefore, we consider the process of a hybrid bevel gear with heat and time-consuming preparation and a hybrid shaft with moderate preparation effort. To compensate for the bevel gear's high cycle times, the shaft is hot-formed during the downtimes. In order to reuse the residual heat of the bevel gear, their hot-forming process run is prioritized: Whenever the bevel gear's workpiece is manufactured, it will be hot-formed immediately. Combining these process chains allows the forming machine's capacity to be fully utilized and energy utilization optimized

Correlations and pair emission in the escape dynamics of ions from one-dimensional traps

We explore the non-equilibrium escape dynamics of long-range interacting ions in one-dimensional traps. The phase space of the few ion setup and its impact on the escape properties are studied. As a main result we show that an instantaneous reduction of the trap's potential depth leads to the synchronized emission of a sequence of ion pairs if the initial configurations are close to the crystalline ionic configuration. The corresponding time-intervals of the consecutive pair emission as well as the number of emitted pairs can be tuned by changing the final trap depth. Correlations between the escape times and kinetic energies of the ions are observed and analyzed.Comment: 17 pages, 9 figure

Variational Principle for Mixed Classical-Quantum Systems

An extended variational principle providing the equations of motion for a system consisting of interacting classical, quasiclassical and quantum components is presented, and applied to the model of bilinear coupling. The relevant dynamical variables are expressed in the form of a quantum state vector which includes the action of the classical subsystem in its phase factor. It is shown that the statistical ensemble of Brownian state vectors for a quantum particle in a classical thermal environment can be described by a density matrix evolving according to a nonlinear quantum Fokker-Planck equation. Exact solutions of this equation are obtained for a two-level system in the limit of high temperatures, considering both stationary and nonstationary initial states. A treatment of the common time shared by the quantum system and its classical environment, as a collective variable rather than as a parameter, is presented in the Appendix.Comment: 16 pages, LaTex; added Figure 2 and Figure

How Phase-Breaking Affects Quantum Transport Through Chaotic Cavities

We investigate the effects of phase-breaking events on electronic transport through ballistic chaotic cavities. We simulate phase-breaking by a fictitious lead connecting the cavity to a phase-randomizing reservoir and introduce a statistical description for the total scattering matrix, including the additional lead. For strong phase-breaking, the average and variance of the conductance are calculated analytically. Combining these results with those in the absence of phase-breaking, we propose an interpolation formula, show that it is an excellent description of random-matrix numerical calculations, and obtain good agreement with several recent experiments.Comment: 4 pages, revtex, 3 figures: uuencoded tar-compressed postscrip

Reflection Symmetric Ballistic Microstructures: Quantum Transport Properties

We show that reflection symmetry has a strong influence on quantum transport properties. Using a random S-matrix theory approach, we derive the weak-localization correction, the magnitude of the conductance fluctuations, and the distribution of the conductance for three classes of reflection symmetry relevant for experimental ballistic microstructures. The S-matrix ensembles used fall within the general classification scheme introduced by Dyson, but because the conductance couples blocks of the S-matrix of different parity, the resulting conductance properties are highly non-trivial.Comment: 4 pages, includes 3 postscript figs, uses revte

Mesoscopic Transport Through Ballistic Cavities: A Random S-Matrix Theory Approach

We deduce the effects of quantum interference on the conductance of chaotic cavities by using a statistical ansatz for the S matrix. Assuming that the circular ensembles describe the S matrix of a chaotic cavity, we find that the conductance fluctuation and weak-localization magnitudes are universal: they are independent of the size and shape of the cavity if the number of incoming modes, N, is large. The limit of small N is more relevant experimentally; here we calculate the full distribution of the conductance and find striking differences as N changes or a magnetic field is applied.Comment: 4 pages revtex 3.0 (2-column) plus 2 postscript figures (appended), hub.pam.94.

Mechanism of delayed double ionization in a strong laser field

When intense laser pulses release correlated electrons, the time delay between the ionizations may last more than one laser cycle. We show that this "Recollision-Excitation with Subsequent Ionization" pathway originates from the inner electron being promoted to a sticky region by a recollision where it is trapped for a long time before ionizing. We identify the mechanism which regulates this region, and predict oscillations in the double ionization yield with laser intensity

Driven Morse Oscillator: Model for Multi-photon Dissociation of Nitrogen Oxide

Within a one-dimensional semi-classical model with a Morse potential the possibility of infrared multi-photon dissociation of vibrationally excited nitrogen oxide was studied. The dissociation thresholds of typical driving forces and couplings were found to be similar, which indicates that the results were robust to variations of the potential and of the definition of dissociation rate. PACS: 42.50.Hz, 33.80.WzComment: old paper, 8 pages 6 eps file