Ashutosh Singh

Molecular self-assembly: 4-formylcoumarins as versatile skeletons for complementary multipoint association via weak (C–H⋯O, C–H⋯F and C–X⋯OC) interactions

The substituted 4-formylcoumarins feature remarkable skeletons for molecular edge-to-edge self-assembly via complementary multipoint weak C–H⋯O, C–H⋯F and C–X⋯OC interactions, as revealed by the X-ray crystal structure analyses of 1–6. It is shown that the formylcoumarins 1–6 can exploit as many as 6–10 weak interactions despite being structurally so simple. The edge-to-edge association via6 complementary hydrogen bonds in 1, 2, and 4 leads to 1-dimensional molecular arrays (tapes/strands), which get interconnected by C–H⋯O/C–X⋯OC noncovalent hydrogen/halogen bonds to form 2-dimensional sheets. The substitution of a hydrogen by fluoro group as in 5 and 6 leads to a dramatic change in the crystal packing, thereby implying the preponderant influence of C–H⋯F interactions over C–H⋯O interactions in at least the cases studied herein.

Nonlinear optical conductivity of a generic two-band system with application to doped and gapped graphene

We present a general formulation to calculate the dynamic optical conductivity, beyond the linear response regime, of any electronic system whose quasiparticle dispersion is described by a two band model. Our phenomenological model is based on the optical Bloch equations. In the steady state regime it yields an analytic solution for the population inversion and the interband coherence, which are nonlinear in the optical field intensity, including finite doping and temperature effects. We explicitly show that the optical nonlinearities are controlled by a single dimensionless parameter which is directly proportional to the incident field strength and inversely proportional to the optical frequency. This identification leads to a unified way to study the dynamical conductivity and the differential transmission spectrum across a wide range of optical frequencies, and optical field strength. We use our formalism to analytically calculate the nonlinear optical conductivity of doped and gapped graphene, deriving the well known universal ac conductivity of

Wave packet dynamics in monolayer MoS 2 with and without a magnetic field

\sigma_0={e^2}/4\hbar

Nonlinear, anisotropic, and giant photoconductivity in intrinsic and doped graphene

in the linear response regime of low optical intensities (or equivalently high frequencies) and non-linear deviations from it which appear at high laser intensities (or low frequencies) including the impact of finite doping and band-gap opening.

Algorithms for faster overlay creation under high growth rate in query network based overlaid multicasting

Abstract We study the dynamics of electrons in monolayer molybdenum disulfide (MoS2), in the absence as well as presence of a transverse magnetic field. Considering the initial electronic wave function to be a minimum uncertainty Gaussian wave packet, we calculate the time dependent expectation value of position and velocity operators analytically. In the absence of the magnetic field, the time dependent average values of position and velocity show damped oscillations dependent on the width of the wave packet. In the presence of a transverse magnetic field, the wave packet amplitude shows oscillatory behaviour over short timescales associated with classical cyclotron orbit, followed by the phenomena of spontaneous collapse and revival over larger timescales. We relate the timescales of these effects based on general arguments. Our results may also be useful, for the interpretation of experiments with trapped ions, as in [R. Gerritsma, G. Kirchmair, F. Zahringer, E. Solano, R. Blatt, C.F. Roos, Nature 463, 68 (2010)], which performs a proof-of-principle quantum simulation of the one-dimensional Dirac equation.

Binding of HgCl2 by tripodal ligands controlled by AgPF6: receptors for the PF6− anion

We present a framework to calculate the anisotropic and non-linear photoconductivity for two band systems with application to graphene. In contrast to the usual perturbative (second order in the optical field strength) techniques, we calculate photoconductivity to all orders in the optical field strength. In particular, for graphene, we find the photoresponse to be giant (at large optical field strengths) and anisotropic. The anisotropic photoresponse in graphene is correlated with polarization of the incident field, with the response being similar to that of a half-wave plate. We predict that the anisotropy in the simultaneous measurement of longitudinal (

Wave packet dynamics in various two-dimensional systems: A unified description

\sigma_{xx}

Multipath Approach for Reliability in Query Network based Overlaid Multicasting.

) and transverse

Nonlinear and anisotropic polarization rotation in two-dimensional Dirac materials

(\sigma_{yx})

Approaches toward Maintaining Bi-connectivity for Resilience in Overlaid Multicasting.

photoconductivity, with four probes, offers a unique experimental signature of the photo-voltaic response, distinguishing it from the thermal-Seebeck and bolometric effects in photoresponse.