Bulletin of the American Physical Society
2011 Annual Meeting of the Four Corners Section of the APS
Volume 56, Number 11
Friday–Saturday, October 21–22, 2011; Tuscon, Arizona
Session D1: Optical Studies of Nanomaterials and Correlated Systems |
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Chair: Rolf Binder, University of Arizona Room: UA Student Union South Ballroom |
Friday, October 21, 2011 2:00PM - 2:12PM |
D1.00001: Exciton Spectroscopy of Mechanically Deformed GaAs Nanomembranes Baijie Gu, Rolf Binder In recent years, the technology to fabricate inorganic nanostructures with curved geometries has made remarkable progress. These low-dimensional nanostructures include cylindrically and spherically bent membranes as well as wrinkled and rolled-up structures. These systems exhibit novel physical properties in terms of their electronic and optical characteristics. Our research focuses on excitonic optical properties of deformed GaAs membranes. We are developing a theoretical framework where the theory of Wannier excitons in thin layers is merged with the theory of elasticity. In our presentation, we present the basic ingredients of our theory and show results that highlight the connection between linear excitonic optical properties and the membrane's deformation-induced strain profile. [Preview Abstract] |
Friday, October 21, 2011 2:12PM - 2:24PM |
D1.00002: Ultrafast carrier dynamics in graphene Adam Roberts, John Foreman, Henry Everitt, Arvinder Sandhu Prior investigation of carrier dynamics in graphene has been limited to the linear regime in graphene's band structure. In this regime the electrons are strongly coupled to phonons and relaxation takes place in the 100s of femtoseconds. We have investigated electronic relaxation from the saddle point in graphene, which shows a remarkably different behavior. At the saddle point, electronic relaxation takes place in the 100s of picoseconds. This timescale is on the order of coupling between the acoustic phonon modes in graphene with the underlying substrate, which supports the graphene sample. We compare the dynamics between the two different regimes in graphene and discuss the role played between the electron phonon interaction in these limits. [Preview Abstract] |
Friday, October 21, 2011 2:24PM - 2:36PM |
D1.00003: Graphene, a material for superfast electronics? Robert Courtney, Shyam Kattel, Boris Kiefer Physics Department, New Mexico State University: The performance of electronic devices has tremendously increased over the last few decades mainly due to miniaturization of electronic components. However, Moore's law suggests that a limiting minimal feature size of microprocessors may be reached as early as 2020. Thus, it is important to search for new technologies that allow overcoming this limitation. One possibility is to explore the feasibility of near speed of light electronics. Traditional metals have Fermi velocity on the order of 2000 km/s while the Fermi velocity of semiconductors is significantly lower. In contrast, the particular electronic structure of graphene may permit much faster electron transport than semiconductors and metals. This effect is due to the linear segments of the electronic dispersion in graphene below the Fermi energy, as opposed to the quadratic dispersion found in other materials. Here we have used density-functional-theory (DFT) to explore the effect of nitrogen doping on the electronic band structure of graphene, and especially its effect on the linear dispersion that is critical for near speed of light electronics. [Preview Abstract] |
Friday, October 21, 2011 2:36PM - 2:48PM |
D1.00004: Analysis of Faraday rotation and magneto-optical transmission in monolayer graphene Xinyang Wang, Igor Shovkovy Graphene, a single atomic layer of graphite, was isolated in 2004. To understand the properties of this two dimensional material is one of the most popular and important research areas in condensed matter and materials physics. The study of optical conductivity in a strong magnetic field provides an interesting response that sheds light on the nature of spontaneous symmetry breaking of an approximate favor symmetry and causes the anomalous quantum Hall effect. We will discuss the possibility of different types of order parameters, associated with the quantum Hall ferromagnetism and magnetic catalysis. We use the results for the optical conductivity to calculate the magneto-optical absorption and the Faraday rotation angle, and compare the results with recent experiments. Also, we present a theoretical prediction for these properties in the regimes not yet explored in experiments. [Preview Abstract] |
Friday, October 21, 2011 2:48PM - 3:00PM |
D1.00005: Electron screening and disorder-induced heating in ultracold neutral plasmas Mary Lyon, Scott Bergeson We report measurements of the influence of electron screening on plasma evolution at early times in ultracold neutral plasmas. Due to their large electrical potential energies and comparatively small kinetic energies, ultracold plasmas occupy a regime of plasma systems which are called ``strongly coupled.'' Ion motion at early times in these ultracold plasmas is dominated by nearest-neighbor Coulomb interactions. The spatial disorder in the initial plasma state gives rise to rapid ion heating. This relaxation, called disorder-induced heating (DIH), limits the strong coupling of the system to order unity. Using laser-induced fluorescence on the ions we map out the time evolution of the velocity distribution by changing the frequency of the laser beam we use to probe the ions. This allows us to study DIH with ns time resolution and to observe and characterize effects due to electron screening on ion equilibration over a wide range of plasma conditions. [Preview Abstract] |
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