Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userRing-shaped luminescence patterns in a locally photoexcited electron-hole bilayer
496
0
0.0
(
0
)
Added by
Alexander Paraskevov
Publication date
2009
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We report the results of molecular dynamics simulation of a spatiotemporal evolution of the locally photoexcited electrons and holes localized in two separate layers. It is shown that the ring-shaped spatial pattern of luminescence forms due to the strong in-layer Coulomb interaction at high photoexcitation power. In addition, the results predict (i) stationary spatial oscillations of the electron density in quasi one-dimensional case and (ii) dynamical phase transition in the expansion of two-dimensional electron cloud when threshold electron concentration is reached. A possible reason of the oscillations and a theoretical interpretation of the transition are suggested.
rate research
Read More
A consistent explanation of the formation of a ring-shaped pattern of exciton luminescence in GaAs/AlGaAs double quantum wells is suggested. The pattern consists of two concentric rings around the laser excitation spot. It is shown that the luminescence rings appear due to the in-layer transport of hot charge carriers at high photoexcitation intensity. Interestingly, one of two causes of this transport might involve self-organized criticality (SOC) that would be the first case of the SOC observation in semiconductor physics. We test this cause in a many-body numerical model by performing extensive molecular dynamics simulations. The results show good agreement with experiments. Moreover, the simulations have enabled us to identify the particular kinetic processes underlying the formation of each of these two luminescence rings.
We consider a semiconductor quantum-well placed in a wave guide microcavity and interacting with the broadband squeezed vacuum radiation, which fills one mode of the wave guide with a large average occupation. The wave guide modifies the optical density of states so that the quantum well interacts mostly with the squeezed vacuum. The vacuum is squeezed around the externally controlled central frequency $om_0$, which is tuned above the electron-hole gap $E_g$, and induces fluctuations in the interband polarization of the quantum-well. The power spectrum of scattered light exhibits a peak around $om_0$, which is moreover non-Lorentzian and is a result of both the squeezing and the particle-hole continuum. The squeezing spectrum is qualitatively different from the atomic case. We discuss the possibility to observe the above phenomena in the presence of additional non-radiative (e-e, phonon) dephasing.
Band structure determines the motion of electrons in a solid, giving rise to exotic phenomena when properly engineered. Drawing an analogy between electrons and photons, artificially designed optical lattices indicate the possibility of a similar band modulation effect in graphene systems. Yet due to the fermionic nature of electrons, modulated electronic systems promise far richer categories of behaviors than those found in optical lattices. Here, we uncovered a strong modulation of electronic states in bilayer graphene subject to periodic potentials. We observed for the first time the hybridization of electron and hole sub-bands, resulting in local band gaps at both primary and secondary charge neutrality points. Such hybridization leads to the formation of flat bands, enabling the study of correlated effects in graphene systems. This work may also offer a viable platform to form and continuously tune Majorana zero modes, which is important to the realization of topological quantum computation.
We consider ground state of electron-hole graphene bilayer composed of two independently doped graphene layers when a condensate of spatially separated electron-hole pairs is formed. In the weak coupling regime the pairing affects only conduction band of electron-doped layer and valence band of hole-doped layer, thus the ground state is similar to ordinary BCS condensate. At strong coupling, an ultrarelativistic character of electron dynamics reveals and the bands which are remote from Fermi surfaces (valence band of electron-doped layer and conduction band of hole-doped layer) are also affected by the pairing. The analysis of instability of unpaired state shows that s-wave pairing with band-diagonal condensate structure, described by two gaps, is preferable. A relative phase of the gaps is fixed, however at weak coupling this fixation diminishes allowing gapped and soliton-like excitations. The coupled self-consistent gap equations for these two gaps are solved at zero temperature in the constant-gap approximation and in the approximation of separable potential. It is shown that, if characteristic width of the pairing region is of the order of magnitude of chemical potential, then the value of the gap in the spectrum is not much different from the BCS estimation. However, if the pairing region is wider, then the gap value can be much larger and depends exponentially on its energy width.
Electron optics in the solid state promises new functionality in electronics through the possibility of realizing micrometer-sized interferometers, lenses, collimators and beam splitters that manipulate electrons instead of light. Until now, however, such functionality has been demonstrated exclusively in one-dimensional devices, such as in nanotubes, and in graphene-based devices operating with p-n junctions. In this work, we describe a novel mechanism for realizing electron optics in two dimensions. By studying a two-dimensional Fabry-P{e}rot interferometer based on a resonant cavity formed in an InAs/GaSb double quantum well using p-n junctions, we establish that electron-hole hybridization in band-inverted systems can facilitate coherent interference. With this discovery, we expand the field of electron optics to encompass materials that exhibit band inversion and hybridization, with the promise to surpass the performance of current state-of-the-art devices.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
