77 research outputs found
Band gap renormalization in photoexcited semiconductor quantum wire structures in the GW approximation
We investigate the dynamical self-energy corrections of the electron-hole
plasma due to electron-electron and electron-phonon interactions at the band
edges of a quasi-one dimensional (1D) photoexcited electron-hole plasma. The
leading-order dynamical screening approximation is used in the calculation
by treating electron-electron Coulomb interaction and electron-optical phonon
Fr\"{o}hlich interaction on an equal footing. We calculate the
exchange-correlation induced band gap renormalization (BGR) as a function of
the electron-hole plasma density and the quantum wire width. The calculated BGR
shows good agreement with existing experimental results, and the BGR normalized
by the effective quasi-1D excitonic Rydberg exhibits an approximate
one-parameter universality.Comment: 11 pages, 3 figure
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Origin of a-plane (Al,Ga)N formation on patterned c-plane AIN/sapphire templates
a-plane (Al,Ga)N layers can be grown on patterned c-plane AlN/sapphire templates with a ridge direction along [1bar 100]Al2O3. Scanning nanobeam diffraction reveals that the formation of a-plane layers can be explained by nucleation of c-plane (Al,Ga)N with [11bar 20](Al,Ga)N[0001]Al2O3 at the ridge sidewalls. Faster growth of the top (11bar 20)(Al,Ga)N facet in the vertical direction leads to the overgrowth of c-plane (Al,Ga)N nucleated on the horizontal ridge and trench surfaces. Phase separation into binary GaN and AlN takes place during the first growth stages. However, this fades out and does not influence the composition of the final thick a-plane (Al,Ga)N layer
Precision determination of band offsets in strained InGaAs/GaAs quantum wells by C-V-profiling and Schroedinger-Poisson self-consistent simulation
The results of measurements and numerical simulation of charge carrier
distribution and energy states in strained quantum wells In_xGa_{1-x}As/GaAs
(0.06 < x < 0.29) by C-V-profiling are presented. Precise values of conduction
band offsets for these pseudomorphic QWs have been obtained by means of
self-consistent solution of Schroedinger and Poisson equations and following
fitting to experimental data. For the conduction band offsets in strained
In_xGa_{1-x}As/GaAs - QWs the expression DE_C(x) = 0.814x - 0.21x^2 has been
obtained.Comment: 9 pages, 12 figures, RevTeX
Shifted Excitation Raman Difference Spectroscopy Applied to Extraterrestrial Particles Returned from the Asteroid Itokawa
Two extraterrestrial particles from the asteroid Itokawa are investigated applying Shifted Excitation Raman Difference Spectroscopy (SERDS). These particles were returned by the Hayabusa mission of the Japanese Space Agency JAXA. For SERDS a diode laser based microsystem light source at 488 nm is used for excitation. It has been found that fluorescence signals masking the Raman spectral features of interest can be substantially separated by applying SERDS. Therefore, SERDS improves the information obtained from the Raman spectra and enables a reliable analysis for investigations on extraterrestrial samples
Extraordinary carrier multiplication gated by a picosecond electric field pulse
The study of carrier multiplication has become an essential part of many-body physics and materials science as this multiplication directly affects nonlinear transport phenomena, and has a key role in designing efficient solar cells and electroluminescent emitters and highly sensitive photon detectors. Here we show that a 1-MVcmâ1 electric field of a terahertz pulse, unlike a DC bias, can generate a substantial number of electronâhole pairs, forming excitons that emit near-infrared luminescence. The bright luminescence associated with carrier multiplication suggests that carriers coherently driven by a strong electric field can efficiently gain enough kinetic energy to induce a series of impact ionizations that can increase the number of carriers by about three orders of magnitude on the picosecond time scale
Im Schatten des Strafrechts : Eine Untersuchung der Mediation in Strafsachen am Beispiel des deutschen TÀter-Opfer-Ausgleichs und der französischen médiation pénale auf der Grundlage von Interaktions- und Kontextanalysen
Mediation in Strafsachen als eine AusprĂ€gungsform der "Restorative Justice" stellt den Versuch dar, einen alternativen, "dritten" Weg zu gehen zwischen Verfahrenseinstellung und Strafverfolgung, bleibt aber gleichwohl eingebunden in strafrechtliche Strukturen und damit der Dominanz des Rechts unterworfen. So muss sie sich mit dem juristischen Rahmen arrangieren und versuchen, dennoch die ihr eigene Verfahrenslogik zu entfalten. Ausgehend von dieser paradoxen Art und Weise der Institutionalisierung wird die Frage aufgeworfen, wie es um die Realisierungschancen der Mediationsidee unter den Bedingungen eines Strafverfahrens bestellt ist. Dazu werden zwei Institutionalisierungsvarianten empirisch untersucht, der deutsche TĂ€ter-Opfer-Ausgleich und die französische "mĂ©diation en matiĂšre pĂ©nale". Auf der Basis authentischer Mitschnitte von deutschen und französischen GesprĂ€chen zwischen TĂ€tern, Opfern und Mediatoren liefern Interaktionsanalysen Erkenntnisse darĂŒber, wie die Akteure unter diesen spezifischen Bedingungen mit der Handlungsaufgabe "Mediation" umgehen
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