Waiting Times and Noise in Single Particle Transport

The waiting time distribution $w(\tau)$, i.e. the probability for a delay $\tau$ between two subsequent transition (`jumps') of particles, is a statistical tool in (quantum) transport. Using generalized Master equations for systems coupled to external particle reservoirs, one can establish relations between $w(\tau)$ and other statistical transport quantities such as the noise spectrum and the Full Counting Statistics. It turns out that $w(\tau)$ usually contains additional information on system parameters and properties such as quantum coherence, the number of internal states, or the entropy of the current channels that participate in transport

Time delayed control of excited state quantum phase transitions in the Lipkin-Meshkov-Glick model

We investigate the role of dissipation in excited state quantum phase transitions (ESQPT) within the Lipkin-Meshkov-Glick model. Signatures of the ESQPT are directly visible in the complex spectrum of an effective Hamiltonian, whereas they get smeared out in the time-dependence of system observables. In the latter case, we show how delayed feedback control can be used to restore the visibility of the ESQPT signals

IMF's assistance: Devil's kiss or guardian angel?

This paper contributes to the debate on the efficacy of IMF's catalytic finance in preventing financial crises. Extending Morris and Shin (2006), we consider that the IMF's intervention policy usually exerts a signaling effect on private creditors and that several interventions in sequence may be necessary to avert an impending crisis. Absent of the IMF's signaling ability, our results state that repeated intervention is required to bail out a country, where by additional assistance may induce moral hazard on the debtor side. Contrarily, if the IMF exerts a strong signaling effect, one single intervention suffices to avoid liquidity crises. --catalytic finance,debtor moral hazard,global games

Dicke Superradiance in a magnetoplasma

We present theoretical results for superradiance, i.e. the collective coherent decay of a radiating system, in a semiconductor heterostructure under a strong quantizing magnetic field. We predict a strong peak (`Dicke-peak') in the emission intensity as a function of time, which should be observable after a short initial excitation of electrons into the conduction band. This peak has a characteristic dependence on the magnetic field and should be observable on sub-picosecond time scales. Furthermore, pumping of electrons and holes into the systems at a rate T leads to a novel kind of oscillations with frequency $\sim \sqrt{T}$ in the limit of the lowest Landau level.Comment: Proc. of HCIS-11, Kyoto(Japan), July 19-23 1999. To appear in Physica

Lasing and antibunching of optical phonons in semiconductor double quantum dots

We theoretically propose optical phonon lasing in a double quantum dot (DQD) fabricated on a semiconductor substrate. No additional cavity or resonator is required. An electron in the DQD is found to be coupled to only two longitudinal optical phonon modes that act as a natural cavity. When the energy level spacing in the DQD is tuned to the phonon energy, the electron transfer is accompanied by the emission of the phonon modes. The resulting non-equilibrium motion of electrons and phonons is analyzed by the rate equation approach based on the Born-Markov-Secular approximation. We show that the lasing occurs for pumping the DQD via electron tunneling at rate much larger than the phonon decay rate, whereas a phonon antibunching is observed in the opposite regime of slow tunneling. Both effects disappear by an effective thermalization induced by the Franck-Condon effect in a DQD fabricated in a suspended carbon nanotube with strong electron-phonon coupling.Comment: 27 pages, 8 figure