Nanocarbons And Quantum Dots Formation In New Hybrid Materials

We present technique of obtaining complex hybrid structures combining the multi-walled carbon nanotubes or multi-layer graphene and luminescent hydrophobic semiconductor core/shell quantum dots CdSe/ZnS. As a result, a formation of quantum dot decorated carbon nanotubes and graphene films is evidenced by 2D microluminescence and micro-Raman mapping of quantum dots and nanocarbons, respectively, where a spatial correlation between the luminescence and Raman signals is found. © 2014 SPIE.912612-02-00938; RFBR; Russian Foundation for Basic Research; 12-02-01263; RFBR; Russian Foundation for Basic ResearchKalantar-Zadeh, K., (2008) Nanotechnology-Enabled Sensors, p. 490. , K. Kalantar-zadeh, B. Fry. New York.: Springer Science & Business Media(1955) Springer Handbook of Nanotechnology, , Ed. B. Bhusha.-New York.: Springer Science & Business Media, 2010, ISBN: 978-3-642-02524-2Cattanach, K., Kulkarni, R.D., Kozlov, M., Manohar, S.K., Flexible carbon nanotube sensors for nerve agent simulants (2006) Nanotechnology, 17, pp. 4123-4128Peng, S., O'Keeffe, J., Wei, C., Cho, K., Kong, J., Chen, R., Franklin, N., Dai, H., Carbon nanotube chemical and mechanical sensors (2001) Proceedings of the 3rd International Workshop on Structural Health Monitoring, pp. 1-8. , USA, September 17-19, 2001, Stanford University, StanfordSnow, E.S., Perkins, F.K., Houser, E.H., Badescu, S.C., Reinecke, T.L., (2005) Science, 307, pp. 1942-1945. , Chemical detection with a single-walled carbon nanotube capacitorStar, A., Joshi, V., Skarupo, S., Thomas, D., Gabriel, J.-C.P., Gas sensor array based on metal-decorated carbon nanotubes (2006) J. Phys. Chem. B, 110, pp. 21014-21020Xu, Z., Gao, H., Guoxin, H., Solution-based synthesis and characterization of a silver nanoparticle-graphene hybrid film Carbon, 49 (14), pp. 4731-4738Cao, A., Liu, Z., Chu, S., Wu, M., Ye, Z., Cai, Z., Chang, Y., Liu, Y., A facile one-step method to produce graphene-cds quantum dot nanocomposites as promising optoelectronic materials (2010) Adv. Mater, 22, pp. 103-106Yang, Y.-K., He, Ch.-E., He, W.-J., Yu, L.-J., Peng, R.-G., Xie, X.-L., Wang, X.-B., Mai, Y.-W., Reduction of silver nanoparticles onto graphene oxide nanosheets with N,Ndimethylformamide and SERS activities of GO/Ag composites (2011) J Nanopart. Res, 13, pp. 5571-5581Lightcap, V., Kamat, P.V., Fortification of cdse quantum dots with graphene oxide. Excited state interactions and light energy conversion (2012) J. Am. Chem. Soc, 134, pp. 7109-7116Ghosh, A., Rao, K.V., Voggu, R., George, S.J., Non-covalent functionalization, solubilization of graphene and single-walled carbon nanotubes with aromatic donor and acceptor molecules (2010) Chemical Physics Letters, 488, pp. 198-201Kim, Y.-T., Han, J.H., Hong, B.H., Kwon, Y.-U., Electrochemical synthesis of cdse quantum-dot arrays on a graphene basal plane using mesoporous silica thin-film templates (2010) Adv. Mater, 22, pp. 515-518Konstantatos, G., Badioli, M., Gaudreau, L., Osmond, J., Bernechea, M., Arquer De Garcia, F.P., Gatti, F., Koppens, L.F.H., Hybrid graphene-quantum dot phototransistors with ultrahigh gain (2012) Nature Nanotechnology, 7, pp. 363-368Wang, Y., Yao, H.-B., Wang, X.-H., Yu, Sh.-H., One-pot facile decoration of CdSe quantum dots on graphene nanosheets: Novel graphene-CdSe nanocomposites with tunable fluorescent properties (2011) J. Mater. Chem, 21, pp. 562-566Murray, C.B., Gaschler, W., Sun, S., Doyle, H., Betley, T.A., Kagan, C.R., Colloidal synthesis of nanocrystals and nanocrystal superlattices IBM J. Res. & Dev., 45 (1), pp. 47-56Ermakov, V.A., Alaferdov, A.V., Vaz, A.R., Baranov, A.V., Moshkalev, S.A., Nonlocal laser annealing to improve thermal contacts between multi-layer graphene and metals (2013) Nanotechnology, 24 (15), p. 15530110Bogdanov, K., Fedorov, A., Osipov, V., Enoki, T., Takai, K., Hayashi, T., Ermakov, V., Moshkalev A, S., Annealing-induced structural changes of carbon onions: High-resolution transmission electron microscopy and Raman studies Baranov Carbon, , 02/201

Field-linked States of Ultracold Polar Molecules

We explore the character of a novel set of ``field-linked'' states that were predicted in [A. V. Avdeenkov and J. L. Bohn, Phys. Rev. Lett. 90, 043006 (2003)]. These states exist at ultralow temperatures in the presence of an electrostatic field, and their properties are strongly dependent on the field's strength. We clarify the nature of these quasi-bound states by constructing their wave functions and determining their approximate quantum numbers. As the properties of field-linked states are strongly defined by anisotropic dipolar and Stark interactions, we construct adiabatic surfaces as functions of both the intermolecular distance and the angle that the intermolecular axis makes with the electric field. Within an adiabatic approximation we solve the 2-D Schrodinger equation to find bound states, whose energies correlate well with resonance features found in fully-converged multichannel scattering calculations

Superfluidity of flexible chains of polar molecules

We study properties of quantum chains in a gas of polar bosonic molecules confined in a stack of N identical one- and two- dimensional optical lattice layers, with molecular dipole moments aligned perpendicularly to the layers. Quantum Monte Carlo simulations of a single chain (formed by a single molecule on each layer) reveal its quantum roughening transition. The case of finite in-layer density of molecules is studied within the framework of the J-current model approximation, and it is found that N-independent molecular superfluid phase can undergo a quantum phase transition to a rough chain superfluid. A theorem is proven that no superfluidity of chains with length shorter than N is possible. The scheme for detecting chain formation is proposed.Comment: Submitted to Proceedings of the QFS2010 satellite conference "Cold Gases meet Many-Body Theory", Grenoble, August 7, 2010. This is the expanded version of V.

Mean-field Phase Diagram of Two-Dimensional Electrons with Disorder in a Weak Magnetic Field

We study two-dimensional interacting electrons in a weak perpendicular magnetic field with the filling factor $\nu \gg 1$ and in the presence of a quenched disorder. In the framework of the Hartree-Fock approximation, we obtain the mean-field phase diagram for the partially filled highest Landau level. We find that the CDW state can exist if the Landau level broadening $1/2\tau$ does not exceed the critical value $1/2\tau_{c}=0.038\omega_{H}$. Our analysis of weak crystallization corrections to the mean-field results shows that these corrections are of the order of $(1/\nu)^{2/3}\ll 1$ and therefore can be neglected

Emergence of quasi-metallic state in disordered 2D electron gas due to strong interactions

The interrelation between disorder and interactions in two dimensional electron liquid is studied beyond weak coupling perturbation theory. Strong repulsion significantly reduces the electronic density of states on the Fermi level. This makes the electron liquid more rigid and strongly suppresses elastic scattering off impurities. As a result the weak localization, although ultimately present at zero temperature and infinite sample size, is unobservable at experimentally accessible temperature at high enough densities. Therefore practically there exists a well defined metallic state. We study diffusion of electrons in this state and find that the diffusion pole is significantly modified due to "mixture" with static photons similar to the Anderson - Higgs mechanism in superconductivity. As a result several effects stemming from the long range nature of diffusion like the Aronov - Altshuler logarithmic corrections to conductivity are less pronounced.Comment: to appear in Phys. Rev.

Pairing in two-dimensional boson-fermion mixtures

The possibilities of pairing in two-dimensional boson-fermion mixtures are carefully analyzed. It is shown that the boson-induced attraction between two identical fermions dominates the p-wave pairing at low density. For a given fermion density, the pairing gap becomes maximal at a certain optimal boson concentration. The conditions for observing pairing in current experiments are discussedComment: 10 pages, 5 figs, revtex

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters