Multi-stack InAs/InGaAs sub-monolayer quantum dots infrared photodetectors Appl. Phys. Lett. 102, 011131 (2013) Optimization of thickness and doping of heterojunction unipolar barrier layer for dark current suppression in long wavelength strain layer superlattice infrared detectors Appl. Phys. Lett. 102, 013509 (2013) Demonstration of high performance bias-selectable dual-band short-/mid-wavelength infrared photodetectors based on type-II InAs/GaSb/AlSb superlattices Appl. Phys. Lett. 102, 011108 (2013) Calculation of interface roughness scattering-limited vertical and horizontal mobilities in InAs/GaSb superlattices as a function of temperatureWe present a theoretical investigation of a double-barrier quantum-well infrared photodetector (QWIP) having two-color selectivity. The quantum well is placed between a pair of potential barriers in order to increase selectivity through modulation of the continuum states. This also leads to a potential decrease in the dark current. Calculations are carried in the effective-mass approximation using a single-electron hamiltonian. The approach used to obtain the photocurrent yields the observation of single as well as many-photon transitions in a unified manner, by naturally accounting for real and virtual processes through intermediate states that take part in the generation of photocurrent. The two-color selectivity of the calculated photocurrent spectra comes from both one-and two-photon transitions. The performance of the system studied is compared to the results for the isolated quantum well and the advantages of the double barrier are pointed out.

The authors present results for the energy spectrum and the dynamical behavior of excitons in an asymmetric quantum dot molecule. Two main resonances are found by using parameters from GaAs-based systems. Excitonic and binding energies are calculated as functions of an external electric field. They fully explore the dynamics of the exciton, showing the time evolution of both the electron and hole components. The effect of the Coulomb interaction is found to be quite dramatic and responsible for considerably large resonance fields as well as for some underlying beatings found in the main oscillation pattern.

We report the existence of regimes of the two-dimensional Fermi liquid that show unusual conservation of the spin current and may be tuned by varying some parameter such as the density of fermions. We show that for reasonable models of the effective interaction the spin current may be conserved in general in 2D, not only for a particular regime. Low-temperature spin waves propagate distinctively in these regimes and entirely new "spin-acoustic" modes are predicted for scatteringdominated temperature ranges. These new high-temperature propagating spin waves provide a clear signature for the experimental search of such regimes. [S0031-9007(99)09124-3] PACS numbers: 71.10. Ay, 75.40.Gb Fermi-liquid theory (FLT) was first introduced by Landau [1] and further developed to include spin waves a long time ago [2]. The progress of FLT in 3D revealed that it is one of the broader theories in condensed matter physics, explaining the experimental results of a wide range of different systems. Recently, interest in FLT regained momentum, driven in part by the discovery of high-temperature superconductors and also by the refinement of experimental techniques in low-dimensional physics. While many results on the (ab)normal phases of the former allow one interpretation that casts doubts on the validity of FLT in 2D [3], the latter has been consolidating a source of examples of practical 2D systems that behave as predicted by 2D FLT, as can be appreciated in the experiments reported in 3 He films [4,5]. This also seems to be the case for doped semiconductors, where thickness and doping can be controlled. Experiments on these charged systems have directly observed expected 2D Fermi-liquid behavior in GaAs heterostructures [6]. This comes from extracting the quasiparticle lifetimes from the tunneling peaks in the current-voltage profile of two biased 2D doped semiconductor contacts with a quantum well between them. The result is the one predicted by 2D FLT [7].Spin waves were observed in bulk alkali metals some three decades ago by conduction-electron spin resonance (CESR) techniques [8], confirming the predictions of FLT [9]. Later, using nuclear magnetic resonance (NMR) in bulk 3 He, Ref.[10] confirmed the existence of the Leggett-Rice effect formerly predicted [11]. The suppression of the Leggett-Rice effect was also indirectly observed for a particular region of the parameter space in bulk 3 He-4 He mixtures [12][13][14], which was pointed out in Ref. [15]. All of these results agree with the known fact that spin current is not conserved in 3D [16]. The majority of these experiments were not repeated for 2D systems up to this date.The central purpose of this Letter is to present exact results indicating that spin current may be a conserved quantity in 2D Fermi liquids, at least for some regions of the parameter space. We will see that for microscopic models that assume short range potentials for the effective interaction spin-current conservation holds for the entire parameter space, so that such models validate the bold stat...

Using ferromagnetic Fermi liquid theory, Bedell and Blagoev derived the collective low-energy excitations of a weak ferromagnet. They obtained the well-known magnon (NambuGoldstone) mode and found a new gapped mode that was never studied in weak ferromagnetic metals. In this article we have identied this mode as the Higgs boson (amplitude mode) of a ferromagnetic metal. This is identied as the Higgs since it can be shown that it corresponds to a uctuation of the amplitude of the order parameter. We use this model to describe the itinerant-electron ferromagnetic material MnSi. By tting the model with the existing experimental results, we calculate the dynamical structure function and see well-dened peaks contributed from the magnon and the Higgs. Our estimates of the relative intensity of the Higgs amplitude mode suggest that it can be seen in neutron scattering experiments on MnSi.