Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session Z22: Focus Session: Carbon Nanotubes, Graphene, & Related Materials |
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Sponsoring Units: DMP Chair: Stephen Cronin, University of Southern California Room: 202A |
Friday, March 6, 2015 11:15AM - 11:51AM |
Z22.00001: Atomtronics: The Application of Organometallic Bis-Hexahapto Bonding to the Electrical Interconnection and Electronic Conjugation of the Graphitic Surfaces of Carbon Nanotubes and Graphene Invited Speaker: Robert Haddon We have demonstrated the functionalization of epitaxial graphene with nitrophenyl groups and by the application of the Kobe reaction. The chemical formation of covalent carbon-carbon bonds involving the basal plane carbon atoms offers an alternative approach to the control of the electronic properties of graphene; the transformation of the carbon centers from sp$^{2}$ to sp$^{3}$ introduces a barrier to electron flow by saturating the carbon atoms and opening a band gap which potentially allows the generation of insulating, semiconducting and magnetic regions in graphene wafers.$^{1}$ This raises the question of the role of covalent bonding in the interconnection of graphitic surfaces and the prospects for the use of such bonds in electronically conjugating neighboring carbon nanotube and graphene surfaces without saturating and destructively rehybridizing the carbon atoms at the point of attachment while simultaneously maintaining the band structures of the intact benzenoid nanostructures. In this talk I will discuss our recent results on the covalent modification of the electronic structure and properties of graphene, and the application of organometallic chemistry to facilitate the interconnection of single-walled carbon nanotubes and to increase the dimensionality of graphitic surfaces. 1. Bekyarova, E.; Sarkar, S.; Wang, F.; Itkis, M. E.; Kalinina, I.; Tian, X.; Haddon, R. C., Effect of Covalent Chemistry on the Electronic Structure and Properties of Carbon Nanotubes and Graphene. Acc. Chem. Res. 2013, 46. [Preview Abstract] |
Friday, March 6, 2015 11:51AM - 12:03PM |
Z22.00002: ABSTRACT WITHDRAWN |
Friday, March 6, 2015 12:03PM - 12:15PM |
Z22.00003: Theory of Chiral Transport in Chiral Carbon Nanotubes Masaki Noro, Jyunya Tanaka, Shuichi Murakami, Takehito Yokoyama In a chiral carbon nanotube, lower crystallographic symmetry allows chiral transport. Namely, when carriers exist by doping, an electric current along the tube axis induces a current around the tube. We calculate the chiral conductivity in carbon nanotubes induced by an electric field along the nanotube axis. We use a tight-binding model for various carbon nanotubes with different chiralities, and apply a constant relaxation time in Boltzmann transport equation. Because the band structure is different for each chiral carbon nanotube, we set electron concentration to be constant to compare quantitatively the chiral conductivity for each nanotube. We find that the chiral conductivity in chiral nanotube is in general non zero, and have either signs depending on their chiralities. We discuss the dependence on the chirality in comparison with the band structure in single-layer graphene, and attribute the chiral transport to the warping of the Fermi surface around the K and K' point in graphene. [Preview Abstract] |
Friday, March 6, 2015 12:15PM - 12:27PM |
Z22.00004: Electron and Optical Spectroscopies of Graphene Nanoribbons on Au(111): Insights from Ab-Initio Calculations Andrea Ferretti, Shudong Wang, Deborah Prezzi, Alice Ruini, Elisa Molinari Narrow graphene nanoribbons (GNRs) exhibit substantial electronic band gaps and optical properties expected to be fundamentally different from the ones of their parent material graphene. Unlike graphene the optical response of GNRs may be tuned by the ribbon width and the directly related electronic band gap. In this work we perform ab initio calculations and compute quasiparticle energies and optical properties of GNRs within the so-called GW-BSE scheme. We focus on a specific armchair nanoribbon (7-AGNR). The presence of the substrate is accounted for by means of a classical image charge model for the screened Coulomb interaction. Our findings show that the metallic substrate induces a significant reduction of the energy gap as compared to the isolated 7-AGNR, bringing the GW gap from 3.7$\pm$0.1 eV to 2.3-2.7 eV on Au(111). On the contrary, the position of the optical peaks remains unaltered. Our results are in very good agreement with the experimental values obtained by STS, ARPES, and differential reflectance data, indicating that this scheme can provide quantitative predictions for electron and optical spectroscopies of nanoribbons on weakly coupled substrates such as Au. [Preview Abstract] |
Friday, March 6, 2015 12:27PM - 12:39PM |
Z22.00005: First-principles calculations of the phonon transport in carbon atomic chain systems based on atomistic Green's function formalism Hu Sung Kim, Yong-Hoon Kim We report on the phonon transport in carbon chain systems, and cumulene. We utilized first-principles calculation with localized atomic basis sets to calculate interatomic forces. Calculated phonon dispersion of polyyne and cumulene were well-matched with theoretical expectations. In addition, we considered the strain effect on the phonon properties of the carbon chain systems. The applied strain affected bond-length alternation (BLA) and force interaction range. Finally, even and odd carbon atomic chains bridging two zigzag graphene nanoribbons were investigated. Increase in the phonon contribution on thermal conductivity was found in case of even carbon chains with proper amount of strain. [Preview Abstract] |
Friday, March 6, 2015 12:39PM - 12:51PM |
Z22.00006: Anomalous transport in nanotubes with resonant adsorbates Didier Mayou, Petruta Anghel-Vasilescu, Guy Trambly de Laissardi\`ere We analyze the quantum diffusion in metallic nanotubes with resonant adsorbates distributed at random with a finite concentration. We show that these nanotubes present a reinforced density of states at the charge neutrality point in a similar way to what is found in grapheme. For wave-packets with various energies the quantum diffusion shows a tendency to localization with a localization length that depends strongly on the energy of the wave-packet. For energies in the peak of the density of state, that is close to the charge neutrality point, the quantum diffusion behaves differently and follows a power law of the time. This suggest that states near the neutrality point are not exponentially localized but are somehow less localized. This behavior is reminiscent of the divergence of the localization length predicted for 2D graphem [1]. Consequences for transport in nanotubes and nanoribbons are briefly discussed [2]. \\[4pt] [1] G.Trambly de Laissardi\`{e}re and D. Mayou Phys. Rev. Lett. 111, 166601 (2013)\\[0pt] [2] Baringhaus et al. , Nature 506, 349 (2014) [Preview Abstract] |
Friday, March 6, 2015 12:51PM - 1:03PM |
Z22.00007: Exploring SAMO states of fullerenes with angle-resolved fs photoelectron spectroscopy Eleanor Campbell, Elvira Bohl, Olof Johansson, Benoit Mignolet, Francois Remacle Femtosecond photoelectron spectroscopy of fullerenes provides a powerful means to study excited Rydberg-like states that cannot be probed via conventional spectroscopy. The photoelectron spectra (PES) show a thermal electron background with a superimposed peak structure for photoelectron kinetic energies that lie below the laser photon energy. The peak structure has been assigned to one-photon ionisation of diffuse low-angular momenta states, so-called superatom molecular orbitals (SAMOs) centred on the hollow fullerene core, based on photoelectron angular distributions (PADs) and TD-DFT calculations. The relative photoionisation probabilities of the s-SAMO to p-SAMO were analysed for photon energies from 2-3.5 eV and showed good agreement with theoretical calculations. Here we look at the photoionisation probabilities and photoelectron angular distributions as a function of laser wavelength and, in particular directly probe the influence of an endohedrally-trapped atom on the photoelectron spectra by directly comparing C60 and Li@C60. We also provide preliminary measurements to probe the timescale for thermal emission prior to coupling to vibrational degrees of freedom. [Preview Abstract] |
Friday, March 6, 2015 1:03PM - 1:15PM |
Z22.00008: Relative stability of excitonic complexes in quasi-one-dimensional semiconductors Igor Bondarev A configuration space approach first implemented in Ref.[1] to evaluate biexciton binding energies in carbon nanotubes (CNs), is developed to obtain the universal asymptotic relations for the lowest energy trion and biexciton binding energies in quasi-1D semiconductors. Trions are shown to be generally more stable (have greater binding energy) than biexcitons in strongly confined quasi-1D structures with small reduced electron-hole masses, while biexcitons are more stable than trions in less confined quasi-1D structures with large reduced electron-hole masses. As such, there is a crossover behavior whereby trions get less stable than biexcitons as the nanostructure transverse size increases $-$ an interesting, quite a general effect which could likely be observed through comparative measurements on semiconducting CNs of increasing diameter. For a specific case of CNs with diameters $\le $ 1 nm, the model predicts the trion binding energy greater than that of the biexciton by a factor $\approx $1.4, decreasing with the CN diameter, thus revealing the general physical principles that underlie recent experimental observations [2,3].\\[4pt] [1] I.V.Bondarev, PRB 83, 153409;\\[0pt] [2] B.Yuma et al., PRB 87, 205412;\\[0pt] [3] L.Colombier et al., PRL 109, 197402. [Preview Abstract] |
Friday, March 6, 2015 1:15PM - 1:27PM |
Z22.00009: Optical detection of highly delocalized superorbitals in fullerenes Guoping Zhang, Yihua Bai, Thomas F. George Superatom molecular orbitals (SAMOs) in $\rm C_{60}$ are a group of highly delocalized orbitals, extending several nanometers outside the carbon cage, but unfortunately they are hard to detect optically. Here we employ three independent first-principles methods to show that the optical detection of SAMOs is possible for the multiphoton excitation, where successive absorptions of photons boost the optical cross section. In the case of the $1f$ orbital, we find that our theoretical photoelectron angular distribution matches the unpublished experimental one quantitatively. Experimental confirmation of our prediction will help explain why the mysterious 4-nm separation between $\rm C_{60}$ and organic compounds is essential to the efficiency of all the fullerene-based organic solar cells. [Preview Abstract] |
Friday, March 6, 2015 1:27PM - 1:39PM |
Z22.00010: Understanding Faceting in Boron-Nitride and Carbon Nanotubes Roberto Guerra, Itai Leven, Andrea Vanossi, Erio Tosatti, Oded Hod Graphite and hexagonal boron nitride (h-BN) are known to share many structural characteristics such as interlayer spacing and bond length, in spite of their completely different atomic bond types, nonpolar homonuclear and strongly polar, respectively. Only recently, a connection of static polarizability and bond polarity with the interlayer spacing and stacking energetics in the two materials has been elucidated [1]. Yet, in the case of curved sheets forming a nanotube (NT), the presence of angular strain and non-uniform stacking between the layers give rise to complex force patterns that subtly differ in the two cases. , by means of classical MD simulations of h-BN and carbon NTs we reveal how the interplay between angular strain and lateral interlayer forces enable the formation of facets in the two materials. The role of the curvature (NT size) and of chirality is discussed along with the important consequences of faceting in the static and frictional properties of multiwall NTs. [1] O. Hod, J. Chem. Theory Comput. 2012, 8, 1360$-$1369 [Preview Abstract] |
Friday, March 6, 2015 1:39PM - 1:51PM |
Z22.00011: The Origin of Negative Thermal Expansion in $sp$-$sp^2$ Hybridized Carbon Systems: Rigid Unit Modes Cheol-Woon Kim, Seoung-Hun Kang, Young-Kyun Kwon Based on first-principles density functional theory, we investigate the thermal expansion behaviors of three kinds ($\alpha$, $\beta$, and $\gamma$) of graphyne, which is two-dimensional carbon allotrope composed of $sp$- and $sp^2$-hybridized bonds. Using quasi-harmonic approximation, their Gibbs free energies are calculated as a function of 2D area and temperature to evaluate their temperature-dependent area variations. We find that all three kinds of graphyne exhibit negative thermal expansion behaviors up to quite high temperature as similarly seen in graphene. Their thermal contraction can be explained partially by the ripple effect as observed in graphene, which seems, however, somewhat insufficient for their much larger thermal contraction than that of graphene. Their anomalously huge thermal contraction behaviors are attributed mainly to unusual phonon modes with a frequency of a few hundreds of cm$^{-1}$, which do not exist in graphene. These modes are identified to ``rigid unit modes (RUMs)'', the librational modes of ``rigid units'' composed only of $sp^2$-bonds. RUMs are unusual in 2D materials, but known to be resposible for the negative thermal expasion in various metal oxides composed of rigid polyhedra, such as MO$_6$, where M is a metal cation. [Preview Abstract] |
Friday, March 6, 2015 1:51PM - 2:03PM |
Z22.00012: Spectroscopy and microscopy of coronene-carbon nanotube hybrid structures Katalin Kamaras, Beata Nagy, Hajnalka Tohati, Bea Botka, Rudi Hackl, Thomas Chamberlain, Andrei Khlobystov The flat, disc-shaped polyaromatic hydrocarbon coronene and its derivatives can form various hybrid structures with carbon nanotubes: its size makes encapsulation possible inside the most abundant carbon nanotubes, and its conjugated $\pi$-electron structure enables $\pi-\pi$ bonding on the surface of the nanotubes. Depending on synthesis conditions, adsorption, encapsulation and polymerization reactions are all possible, resulting in coronene-based polymers, graphene nanoribbons or double-walled carbon nanotubes. Synthesis and characterization of such hybrid structures will be reported. Synthesis variations included sublimation temperature and exchanging the hydrogen atoms on the perimeter of the molecule for other atoms. Characterization was performed by transmission electron microscopy, as well as infrared, Raman and photoluminescence spectroscopy. We will present how synthesis conditions affect the reaction of the molecular species to form polymers or nanoribbons. We find that the nanotube surface catalyses the polymerization of coronene, and that non-carbon atoms other than hydrogen on the perimeter facilitate nanoribbon formation. [Preview Abstract] |
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