arXiv subjects

T. Brandes

Publications and source records attributed to T. Brandes.

60 records · Page 4Linked to original sources

arXiv2001

Decay rate and renormalized frequency shift of a quantum wire Wannier exciton in a planar microcavity

The superradiant decay rate and frequency shift of a Wannier exciton in a one-dimensional quantum wire are studied. It is shown that the dark mode exciton can be examined experimentally when the quantum wire is embedded in a planar microcavity. It is also found that the decay rate is greatly enhanced as the cavity length $L_{c}$ is equal to the multiple wavelength of the emitted photon. Similar to its decay rate counterpart, the frequency shift also shows discontinuities at resonant modes.

cond-mat.mes-hall↗

arXiv2001

Adiabatic steering and determination of dephasing rates in double dot qubits

We propose a scheme to prepare arbitrary superpositions of quantum states in double quantum--dots irradiated by coherent microwave pulses. Solving the equations of motion for the dot density matrix, we find that dephasing rates for such superpositions can be quantitatively infered from additional electron current pulses that appear due to a controllable breakdown of coherent population trapping in the dots.

cond-mat.mes-hall↗

arXiv2000

Phonons and Phonon Confinement in Transport through Double Quantum Dots

We calculate the electron-phonon interaction coefficients for surface acoustic waves and for phonons in free standing quantum wells. These are used to derive the inelastic current through a double quantum dot caused by spontaneous emission of phonons. For the case of the free standing structure (phonon cavity), we predict a staircase-like inelastic current superimposed by van Hove singularities. Therefore, the phonon confinement can be detected by electron transport measurements.

cond-mat.mes-hall↗

arXiv2000

Current Switch by Coherent Trapping of Electrons in Quantum Dots

We propose a new transport mechanism through tunnel-coupled quantum dots based on the coherent population trapping effect. Coupling to an excited level by the coherent radiation of two microwaves can lead to an extremely narrow current antiresonance. The effect can be used to determine interdot dephasing rates and is a mechanism for a very sensitive, optically controlled current switch.

cond-mat.mes-hall↗

arXiv1999

Dicke-superradiance in electronic systems coupled to reservoirs

We present theoretical results for superradiance, i.e. the collective coherent decay of a radiating system, in semiconductor structures. An optically active region can become superradiant if a strong magnetic field is applied. Pumping of electrons and holes at a rate T through coupling to external `reservoirs' leads to a novel kind of oscillations with frequency $\sim \sqrt{T}$.}

cond-mat.mes-hall↗

arXiv1998

Oscillatory behavior of a superradiating system coupled to electron reservoirs

We investigate a superradiating system coupled to external reservoirs. Under conditions where electrons tunneling at a rate $T$ act like an electron pump, we predict a novel phenomenon in the form of oscillations with a frequency $ω\simeq \sqrt{2ΓT}$ that appear in the (photon) emission intensity, where $Γ$ is the spontaneous decay rate of a single two-level system. The effect, together with a strong enhancement of the superradiant peak, should be observable in semiconductor quantum wells in strong magnetic fields, or in quantum dot arrays.

cond-mat.mes-hall↗