Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session B27: Focus Session: Carbon Nanotubes: Optical Properties II |
Hide Abstracts |
Sponsoring Units: DMP Chair: Vasili Perebeinos, IBM Room: LACC 501C |
Monday, March 21, 2005 11:15AM - 11:27AM |
B27.00001: Photoconductivity of Single-Walled Nanotubes on Quartz Substrates O.M. Castellini, Matthew S. Marcus, J.M. Simmons, M.A. Eriksson Photoconductivity measurements are used to study the electrical properties of carbon nanotubes on quartz substrates. Fabricating nanotube devices on quartz allows a measurement of the intrinsic photocurrent without any contribution from the substrate. We measure photocurrents of order nanoamps and a lower limit for the rise time of a SWNT diode device. Various measured rise times range from fast ($<$ 5 $\mu $s) to slow (800 $\mu $s), indicating that nanotube devices may be useful for high speed applications, but that the device configuration may play a critical role in the minimum achievable rise time. The special considerations for fabricating single nantoube devices on quartz will also be discussed. [Preview Abstract] |
Monday, March 21, 2005 11:27AM - 11:39AM |
B27.00002: Interband Magneto-Optics in Carbon Nanotubes in Pulsed High Magnetic Fields S. Zaric, G.N. Ostojic, J. Kono, O. Portugall, P. Frings, G. Rikken, S.A. Crooker, M. Furis, X. Wei, H.U. Mueller, M. Von Ortenberg, V.C. Moore, J. Shaver, R.H. Hauge, R.E. Smalley To extend our earlier work\footnote{S.~Zaric {\it et al}., Science {\bf 304}, 1129 (2004).} on the Aharonov-Bohm effect in carbon nanotubes to higher fields, we have performed interband magneto-absorption and magneto-photoluminescence experiments in micelle-suspended single-walled carbon nanotubes in pulsed high magnetic fields up to 71 T. Because of their anisotropic magnetic susceptibilities, the nanotubes dynamically align in response to the pulsed magnetic fields, exhibiting time- dependent optical anisotropy. At fields above $\sim$60 T, we observe clear splittings of absorption peaks, a signature of the Aharonov-Bohm effect. The amount of splitting as a function of magnetic field will be discussed by taking into account the time-dependent angular distribution of the nanotubes. Furthermore, the relative intensities of the split peaks will be examined in light of recent theories predicting field-dependent oscillator strengths. [Preview Abstract] |
Monday, March 21, 2005 11:39AM - 11:51AM |
B27.00003: Carbon Nanotube- Polyvinylalcohol Composite Film as Nonlinear Optical Device: Application to Femtosecond Mode-Locked Fiber Laser Madoka Tokumoto, Aleksey Rozhin, Youichi Sakakibara, Yohji Achiba, Hiromichi Kataura Saturable absorption of single-wall carbon nanotubes (SWNTs) in near-infrared region [1] is very promising as a passive mode-locker for pico- or subpicosecond pulsed Er-doped fiber lasers [2]. In this work, we fabricated SWNT/polyvinylalcohol (PVA) nanocomposite self-standing films [3] for saturable absorption devices, and used as a mode-locker for Er-doped fiber short pulse lasers. We integrated a 35-$\mu $m-thick SWNT/PVA composite film into a conventional FC/PC fiber connection adaptor, where the film is sandwiched by a pair of fiber ferrules. A ring cavity fiber laser inserted with the SWNT/PVA saturable absorber operated very easily in mode-locked short pulse mode with a pulse width as short as 210 fs, which, to our knowledge, is the shortest in this class of lasers using carbon nanotube saturable absorbers. This result demonstrates that the SWNT/PVA composite film is very promising as a passive mode-locker for femtosecond Er-doped fiber lasers. [1] Y. Sakakibara et al.: Jpn. J. Appl. Phys. 42 (2003) L494. [2] S. Y. Set et al.: OSA Trends in Optics and Photonics Vol.86, Optical Fiber Commun. Conf., Tech. Dig., Postconf. Ed., pd44. [3] A. G. Rozhin et al.: Thin Solid Films 464-465 (2004) 368. [Preview Abstract] |
Monday, March 21, 2005 11:51AM - 12:27PM |
B27.00004: Chiral Dependent Optical Properties of Carbon Nanotubes Invited Speaker: We have carried out both empirical tight-binding (TB) and first-principles local-density functional (LDF) results for the electronic structure and predicted optical spectra of semiconducting single-walled carbon nanotubes (SWNT) for a range of diameters and chiralities. We have also carried out explicit calculations of the optical cross-sections for polarizations parallel and transverse to the nanotube axis. Recent photoluminescence experiments on these materials have been used to make assignments of the SWNT conformations based on tight-binding models for the excitation gap, E$_{11}$, between the van Hove singularities nearest the Fermi level, and the excitation gap, E$_{22}$, between the next set of van Hove singularities. Our results for the E$_{11}$ and E$_{22}$ gaps using these approaches show a strong dependence of the excitation spectra on the radius with a weak dependence on the chirality.. Although the TB and LDF results share similar dependence on the radius, the chirality dependence of the ratio E$_{22}$/E$_{11}$ versus E$_{22}$ differs substantially. We discuss and compare these results in light of other theoretical and experimental work on the optical properties of carbon nanotubes. This work was supported by the US Office of Naval Research, the DoD HPCMO CHSSI program through the Naval Research Laboratory, and Oklahoma State University. [Preview Abstract] |
Monday, March 21, 2005 12:27PM - 12:39PM |
B27.00005: Many-electron effects in the optical properties of single-walled carbon nanotubes Catalin D. Spataru, Sohrab Ismail-Beigi, Rodrigo B. Capaz, Steven G. Louie Recent optical measurements on single-wall carbon nanotubes (SWCNT) showed anomalous behaviors that are indicative of strong many-electron effects. To understand these data, we performed ab initio calculation of self-energy and electron-hole interaction (excitonic) effects on the optical spectra of several SWCNTs. We employed a many-electron Green's function approach that determines both the quasiparticle and optical excitations from first principles. We found important many-electron effects that explain many of the puzzling experimental findings in the optical spectrum of these quasi-one dimensional systems, and are in excellent quantitative agreement with measurements. We have also calculated the radiative lifetime of the bright excitons in these tubes. Taking into account temperature effects and the existence of dark excitons, our results explain the radiative lifetime of excited nanotubes measured in time- resolved fluorescence experiments. This work was supported by the NSF under Grant No. DMR04-39768, and the U.S. DOE under Contract No. DE-AC03-76SF00098. Computational resources have been provided by NERSC and NPACI. RBC acknowledges financial support from the Guggenheim Foundation and Brazilian funding agencies CNPq, CAPES, FAPERJ, Instituto de Nanoci{\^e}ncias, FUJB-UFRJ and PRONEX-MCT. [Preview Abstract] |
Monday, March 21, 2005 12:39PM - 12:51PM |
B27.00006: Optical Spectra and Excitonic Effect of Nanostructured Materials Young-Kyun Kwon, Catalin D. Spataru, James R. Chelikowsky, Marvin L. Cohen, Steven G. Louie To investigate the optical spectra and excitonic effect of various nanostructured materials, we solve the Bethe-Salpeter equation (BSE) of the two-particle Green's function employing one-particle input from either GW approximation (GWA) calculations or the empirical pseudopotential method (EPM). We will present a comparative study of results from these two approaches. We will discuss the absorption spectra and excitonic effects of various structures of silicon and carbon materials including nanowires and nanotubes. [Preview Abstract] |
Monday, March 21, 2005 12:51PM - 1:03PM |
B27.00007: Electron-electron interaction effects on the optical excitations of single-walled carbon nanotubes Sumit Mazumdar, Hongbo Zhao We report correlated-electron calculations of optically excited states in ten semiconducting single-walled carbon nanotubes (SWCNTs) with a wide range of diameters.\footnote{Hongbo Zhao and Sumit Mazumdar, Phys. Rev. Lett. {\bf 93}, 157402 (2004)} First, we show that optical excitation in SWCNTs occurs to excitons whose binding energies decrease with the increasing nanotube diameter, and are smaller than the binding energy of an isolated strand of poly-(paraphenylenevinylene), (PPV). Second, electron-electron interactions split the degeneracies characteristic of cylindrical geometries, and in all cases there occur forbidden excitons below the optical exciton. We ascribe the experimentally observed low quantum efficiency of the photoluminescence of SWCNTs to the presence of these forbidden states. Third, while within one-electron theory the transverse photo-excitations occur exactly halfway between the two lowest longitudinally polarized absorptions, they are shifted to considerably above the central region for nonzero electron-electron interactions. Finally, the ratio of the threshold energy of the second longitudinally polarized optical absorption to that of the lowest such transition in the widest SWCNTs is less than 2 within correlated-electron theory, in agreement with experiments. [Preview Abstract] |
Monday, March 21, 2005 1:03PM - 1:15PM |
B27.00008: Coulomb effect and nonlinear optical properties of single-walled carbon nanotubes Hongbo Zhao, Sumit Mazumdar We investigated theoretically nonlinear optical properties of ten single-walled carbon nanotubes (SWCNTs) with a wide range of diameters, within a semiempirical Pariser-Parr-Pople model with a long- range Coulomb interaction. The excited states are calculated within Single Configuration Interaction (SCI) scheme. In our previous work \footnote{Hongbo Zhao and Sumit Mazumdar, Phys. Rev. Lett. {\bf 93}, 157402 (2004)} we have shown that there occur dark exciton states below the first optically allowed exciton, and that this is the reason for low photoluminescence quantum efficiency. In the present work we report calculations of photoinduced absorption (PA) from both dark and optically allowed lowest excitons for a mixture of SWCNTs, and compare our result with experimental ultrafast PA spectra. As with $\pi$-conjugated polymers, the lowest PA energies give lower bounds to the exciton binding energies. Our SCI calculations do not take into account double excitations, and hence we are unable to describe the high energy PA in SWCNTs. We speculate that the origin of the high energy PA is the same as in PPV. \footnote{A. Shukla, H. Ghosh and S. Mazumdar, Phys. Rev. B {\bf 67}, 245203 (2003)} [Preview Abstract] |
Monday, March 21, 2005 1:15PM - 1:27PM |
B27.00009: Temperature Dependence of the Band Gap of Semiconducting Carbon Nanotubes Rodrigo B. Capaz, Paul Tangney, Catalin D. Spataru, Marvin L. Cohen, Steven G. Louie The temperature dependence of the band gap of semiconducting single-wall carbon nanotubes (SWNTs) is calculated by direct evaluation of electron-phonon couplings within a ``frozen-phonon'' scheme. An interesting diameter and chirality dependence of $E_g(T)$ is obtained, including non-monotonic behavior for certain tubes and distinct ``family'' behavior. These results are traced to a strong and complex coupling between band-edge states and the lowest-energy optical phonon modes in SWNTs. The $E_g(T)$ curves are modeled by an analytic function with diameter and chirality dependent parameters; these provide a valuable guide for systematic estimates of $E_g(T)$ for any given SWNT. Magnitudes of the temperature shifts at 300 K are smaller than 12 meV and should not affect $(n,m)$ assignments based on optical measurements. RBC acknowledges financial support from the John Simon Guggenheim Memorial Foundation and Brazilian funding agencies CNPq, FAPERJ, Instituto de Nanoci{\^e}ncias, FUJB-UFRJ and PRONEX-MCT. Work partially supported by NSF Grant No. DMR00-87088 and DOE Contract No. DE-AC03-76SF00098. Computer resources were provided by NERSC and NPACI. [Preview Abstract] |
Monday, March 21, 2005 1:27PM - 1:39PM |
B27.00010: The physics behind the family behavior of optical transition energies in single-wall carbon nanotubes Georgii Samsonidze, Riichiro Saito, Jie Jiang, Alexander Gr\"{u}neis, Ado Jorio, Shin Grace Chou, Gene Dresselhaus, Mildred Dresselhaus Experimental optical spectroscopy studies of single-wall carbon nanotubes (SWNTs) revealed $2n{+}m{=}$constant family patterns in the electronic transition energies. Meanwhile, the family behavior remained unexplained within the simple tight-binding approximation that has been commonly used for calculations of the SWNT band structure. We here present calculations for the optical transition energies in SWNTs using an extended tight- binding approximation which allows optimization of C-C bond lengths and bond angles along with the many-body corrections reported in the literature. Our calculations closely reproduce the experimentally observed family behavior, and find that the family behavior can be attributed to the collective effect of curvature-induced rehybridization, long-range atomic interactions, geometrical structure relaxation, and many-body interactions. Our calculations clarify controversial results concerning the magnitude of quasiparticle corrections and exciton binding energies in SWNTs. [Preview Abstract] |
|
B27.00011: Exciton Phonon Coupling and G-Band Resonance Observed by Photoluminescence Spectroscopy in Single Walled Carbon Nanotubes Flavio Plentz, Henrique Ribeiro, Cristiano Fantine, Marcos Pimenta, Ado Jorio, Michael Strano One dimensional systems, such as Single Walled Carbon nanotubes (SWNT), show very interesting optical properties. For certain values of energies, the gradient of $E(\vec {k})$vanishes and the density of states (DOS) diverges. These are known as van Hove Singularities (VHS). In the case of SWNT's that are semiconductors, efficient photoluminescence (PL) can be observed when they are isolated in stable suspensions by the use of surfactants or wrapped by macromolecules such as DNA. In semiconducting SWNT's excitonic effects are very strong and binding exciton energies up to 1eV are expected. For that reason it is expected that excitonic effects dominate the processes of absorption and emission of light. In this case resonant behavior of the PL is observed when the excitation energy matches the excitonic bound states associated with each vHS. In SWNT's strong exciton-phonon coupling is also expected due to de 1D character of the system. In this work we performed PLE measurements in surfactant-suspended SWNT's using laser energy from 1.20eV to 1.75eV and measuring emission from 0.8eV to 1.45eV. Several already observed resonances were measured and allowed us determine which tubes are in the sample. Phonon-assisted PL were also observed crossing all over the map and are identified as originating from exciton-phonon coupling SWNT's. The brazilian authors acknowledge CNPq, FINEP and FAPEMIG [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700