Description: This article discusses the coherent control of refraction index in far-detuned Λ systems. Abstract: Enhancement and control of the index of refraction in a mixture of two three-level atomic species that form a pair of far-detuned Λ schemes under two-photon resonance and has been studied. We employ the density-matrix approach to properly take population relaxation into account and to describe the interaction of each Λ system with the electromagnetic fields. Both Λ systems are driven by a corresponding far-detuned coherent field at one atomic transition and are probed by the same weak field. In the dressed-state basis, it represents a superposition of effective two-level subsystems with the positions, widths, and amplitudes of the resonances controlled by the driving fields and allows for efficient control of the susceptibility of the total system; leading to refractive index (RI) enhancement with vanishing absorption in the absence of amplification. We analyze the experimental implementation of such a system in a cell of Rb atoms with a natural abundance of isotopes. An upper limit estimate of the RI enhancement is obtained.

Description: This article discusses electron transport properties of bilayer graphene. Abstract: Electron transport in bilayer graphene is studied by using a first-principles analysis and the Monte Carlo simulation under conditions relevant to potential applications. While the intrinsic properties are found to be much less desirable in bilayer than in monolayer graphene, with significantly reduced mobilities and saturation velocities, the calculation also reveals a dominant influence of extrinsic factors such as the substrate and impurities. Accordingly, the difference between two graphene forms is more muted in realistic settings, although the velocity-field characteristics remain substantially lower in the bilayer. When bilayer graphene is subject to an interlayer bias, the resulting changes in the energy dispersion lead to stronger electron scattering at the bottom of the conduction band. The mobility decreases significantly with the size of the generated band gap, whereas the saturation velocity remains largely unaffected.

Description: This article discusses experimental observation of carrier-envelope-phase effects by multicycle pulses. Abstract: We present an experimental and theoretical study of carrier-envelope-phase (CEP) effects on the population transfer between two bound atomic states interacting with pulses consisting of many cycles. Using intense radio-frequency pulse with Rabi frequency of the order of the atomic transition frequency, the authors investigate the influence of the CEP on the control of phase-dependent multiphoton transitions between the Zeeman sublevels of the ground state of ⁸⁷Rb. Our scheme has no limitation on the duration of the pulses. Extending the CEP control to longer pulses creates interesting possibilities to generate pulses with accuracy that is better than the period of optical oscillations.

Description: In this article, the authors discuss the propagation of symmetric and antisymmetric Josephson plasma waves in a slab of layered superconductor clad between two identical dielectrics. The authors predict two branches of surface waves in the terahertz frequency range, one above and another below the Josephson plasma frequency. Apart from this, there exists a discrete set of waveguide modes with electromagnetic fields oscillating across the slab thickness and decaying exponentially away from the slab. The authors consider the excitation of the predicted waves by means of the attenuated-total-reflection method. It is shown that for a specific set of the parameters of the structure, the excitation of the waveguide modes is accompanied by the total suppression of specular reflection.

Description: In this article, the authors study the transport of information between two complex systems with similar properties. Both systems generate non-Poisson renewal fluctuations with a power-law spectrum 1/f 3-μ, the case μ=2 corresponding to ideal 1/f noise. The authors denote by μs and μp the power-law indexes of the system of interest S and the perturbing system P, respectively. By adopting a generalized fluctuation-dissipation theorem (FDT) the authors show that the ideal condition of 1/f noise for both systems corresponds to maximal information transport. The authors prove that to make the system S respond when μs < 2 the authors have to set the condition μp < 2. In the latter case, if μp < μs, the system S inherits the relaxation properties of the perturbing system. In the case where μp > 2, no response and no information transmission occurs in the long-time limit. The authors consider two possible generalizations of the fluctuation dissipation theorem and show that both lead to maximal information transport in the condition of 1/f noise.