Market Power and Collusion on Interconnection Phone Market in Tunisia : What Lessons from International Experiences

We try in this paper to characterize the state of mobile phone market in Tunisia. Our study is based on a survey of foreign experience (Europe) in detecting collusive behavior and a comparison of the critical threshold of collusion between operators in developing countries like Tunisia. The market power is estimated based on the work of Parker Roller (1997) and the assumption of "Balanced Calling Pattern". We use then the model of Friedman (1971) to compare the critical threshold of collusion. We show that the "conduct parameter" measuring the intensity of competition is not null during the period 1993-2011. Results show also that collusion is easier on the Tunisian market that on the Algerian, Jordanian, or Moroccan one

Phonon-driven spin-Floquet magneto-valleytronics in MoS2

Two-dimensional materials equipped with strong spin-orbit coupling can display novel electronic, spintronic, and topological properties originating from the breaking of time or inversion symmetry. A lot of interest has focused on the valley degrees of freedom that can be used to encode binary information. By performing ab initio time-dependent density functional simulation on MoS2, here we show that the spin is not only locked to the valley momenta but strongly coupled to the optical E '' phonon that lifts the lattice mirror symmetry. Once the phonon is pumped so as to break time-reversal symmetry, the resulting Floquet spectra of the phonon-dressed spins carry a net out-of-plane magnetization (approximate to 0.024 mu(B) for single-phonon quantum) even though the original system is non-magnetic. This dichroic magnetic response of the valley states is general for all 2H semiconducting transition-metal dichalcogenides and can be probed and controlled by infrared coherent laser excitation

Controlling the Stability and the Electronic Structure of Transition Metal Dichalcogenide Single Layer under Chemical Doping

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Tuning the Magnetic and Electronic Properties of Monolayer Chromium Tritelluride through Strain Engineering

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Electronic structure of two-dimensional transition metal dichalcogenide bilayers from ab initio theory

International audienceBy means of first-principles GW calculations, we have studied the electronic structure properties of MX2 (M = Mo, W; X = S, Se, Te) bilayers, including hybrid structures of MX2 building blocks. The effect of spin-orbit coupling on the electronic structure and the effect of van der Waals interaction on the geometry were taken into account. All the homogeneous bilayers are identified as indirect band-gap materials, with an increase of the band gap when Mo is changed to W, and a decrease of the band gap when the atomic number of X is increased. The same behavior is also observed for hybrid bilayers with common chalcogen atoms, while bilayers with common metal atoms have a direct band gap. Finally, it is shown that due to their particular band alignment, some heterobilayers enable electron-hole separation, which is of interest for solar cell applications

A theoretical study of band structure properties for III-V nitrides quantum wells

Reliable and precise knowledge about the strain and composition effects on the band structure properties is crucial for the optimization of InGaN based heterostructures for electronic and optoelectronic device applications. AlInGaN as quaternary barrier material permits to control the band gap and the lattice constant independently. Using the model solid theory and the multi-band k.p interaction model, we investigate the composition effects on band offsets and band structure for pseudomorphic Ga1−xInxN/AlzInyGa1−y−zN (001) heterointerfaces having zinc-blende structure. The results show that both conduction and valence band states are strongly modified while varying In and Al contents in the well and barrier materials. Furthermore, it is found that using AlInGaN as the barrier material allows the design of heterostructures including InGaN wells with tensile, zero or compressive strain. Such results give new insights for III-nitride compounds based applications and especially may guide the design of white-light emission diodes

Vibrational Properties of CuO and Cu₄O₃ from First-Principles Calculations, and Raman and Infrared Spectroscopy

A combined experimental and theoretical study is reported on the vibrational properties of tenorite CuO and paramelaconite Cu₄O₃. The optically active modes have been measured by Raman scattering and infrared absorption spectroscopy. First-principles calculations have been carried out with the LDA+U approach to account for strong electron correlation in the copper oxides. The vibrational properties have been computed ab initio using the so-called direct method. Excellent agreement is found between the measured Raman and infrared peak positions and the calculated phonon frequencies at the Brillouin zone center, which allows the assignment of all prominent peaks of the Cu₄O₃ spectra. Through a detailed analysis of the displacement eigenvectors, it is shown that a close relationship exists between the Raman modes of CuO and Cu₄O₃