City College of New York, Physics Department - Colloquia and Seminars ********************************************************************** ************************************************************************* The City College of New York Physics Department Seminars and Colloquia Fall Semester 2009 ************************************************************************* Week of Aug. 24, 2009 Fri., Aug 28 2009 First Day of Classes Week of Aug. 31, 2009 Wed. Sep. 2, 2009 Week of Sep. 7, 2009 Wed. Sep. 9, 2009 4:00 pm MR418N Colloquium [JB] Harry Lipkin, Weiszman Institute "Why do neutrinos oscillate? They can't if energy and momentum are conserved!" Abstract: Textbooks consider oscillations arising from a mixed coherent state containing with different masses. They do not consider how such a mixed coherent state can be created. Oscillations cannot arise from decay of an isolated one particle state if four-momentum is conserved. The transition matrix element is generally squared and summed over all final states with no interference between orthogonal final states. Oscillations can exist only if energy conservation is violated! Energy violation by time-uncertainty principle is needed! An initial state containing two components with different energies decay into two orthogonal states with different masses. Although these are completely separated at long times with no interference, interference can arise at times much shorter than decay lifetime when their widths are much broader than their natural line width. Broadened energy spectra of two amplitudes overlap and interfere. The "Darmstadt oscillation" experiment measures the momentum difference between two contributing coherent initial states and obtains mass information without detecting. A simple very approximate calculation gives a value for the squared mass difference differing by less than a factor of three from values calculated from the KAMLAND experiment. This treatment holds only in the laboratory frame with values of energy, time and momentum determined by the experimental environment at rest in the laboratory. Lorentz transformations including the environment are not feasible. Lorentz covariant descriptions based on relativistic quantum field theory cannot describe interference between orthogonal states with different masses producing oscillations. Week of Sep. 14, 2009 Wed. Sep. 16, 2009 12:15pm MR418N Solid State Seminar [MPS] Professor Yuhang Ren, Hunter College "Femtomagnetism: Spin Dynamics in Magnetic Nanostructures" Abstract: Magnetic recording is rapidly approaching the nanometer scale as storage densities are projected to increase to a terabit per square inch. High volume of data requires higher data transfer rates. These present new challenges and opportunities in nanometer scale materials engineering and in understanding the magnetic properties of nanometer scale magnetic materials. We use ultrafast optical techniques to study the surface/interface magnetism and spin wave precessions in magnetic nanostructures. We show that time-resolved optical spectroscopy is an extremely powerful probe of the rich spin dynamics of magnetic nanostructures, as it is capable of revealing key details concerning dynamical responses. The concepts and principles forming the results will be presented in the talk. Wed. Sep. 16, 2009 4:00pm MR418N Colloquium Prof. Daniel Greenberger, CCNY "Exactly What Did Max Planck Do?" Abstract: In Dec. 1900, Max Planck introduced the quantum of action. Most physicists believe that he also quantized the Harmonic Oscillator and introduced the idea of energy levels into physics. But in fact, his relationship to the quantization of anything was very strange, and remained so for the next 13 years. Reading the actual papers and books of this very reluctant revolutionary leads to the inescapable conclusion that he was very innovative, but that he never quantized anything physical. That was left to Einstein, for both waves and particles. Week of Sep. 21, 2009 Wed. Sep. 23, 2009 12:15 pm, MR418N Solid State Seminar [MPS] Prof. Sergey A. Vitkalov, City College of New York "TRANSPORT OF 2D ELECTRONS IN QUANTIZING MAGNETIC FIELDS" Abstract: Nonlinear resistance of highly mobile two-dimensional electrons placed in crossed electric and strong magnetic fields attracts considerable contemporary interest. The resistance shows unusually strong and nontrivial dependence on the electric field E both in microwave and in dc responses. At small electric fields the resistance demonstrates impressive decrease by several times with the electric field, which is unusual for degenerate electron systems. A higher electric field induces appreciable oscillations of the resistance both with the electric and the magnetic fields. Zero resistance and zero differential resistance states of the 2D electrons are observed in these strongly nonlinear systems. In the talk I will discuss current state in this field. In addition I will present our recent results on low-temperature magnetotransport of two-dimensional electrons occupying two subbands in GaAs single quantum well. Two series of Shubnikov-de Haas oscillations are found to be accompanied by magneto-intersubband oscillations, periodic in the inverse magnetic field. We show that strong temperature suppression of the oscillations comes from electron-electron interactions. Our results indicate that the sensitivity to electron-electron scattering is the fundamental property of magnetoresistance oscillations originating from second-order Dingle factor. Wed. Sep. 23, 2009 Colloquium 4:00 p.m., Rm. 418N (RK) Eric R. Dufresne Departments of Mechanical Engineering, Chemical Engineering, Physics and Cell Biology, Yale University "Electrostatics meets entropy" Abstract: Electrostatic forces drive systems with free charges toward charge neutrality. However, entropy can drive persistent charge separation over nanometer and micrometer length scales. This is typically manifested as charged molecules or interfaces dressed with a diffuse layer of counterions. Such charge separation underlies the structure of polymers and proteins, the stability of suspensions and even our nervous system’s ability to process information. We study electrostatic interactions over short length scales, deep inside the diffuse counterion cloud. Our model system consists of micron-sized plastic particles floating in oil. The surfaces of these particles spontaneously charge at room temperature under appropriate solvent conditions. We exploit optical forces and thermal fluctuations to measure femtoNewton scale repulsive electrostatic forces between the particles. Interestingly, the repulsion between any pair of particles can be strongly reduced when other particles are nearby. This many-body effect is not accounted for by the usual suspects: nonlinearity in the Poisson-Boltzmann equation or counter-ion correlations. Instead, we can quantitatively predict interparticle forces in a variety of geometries by simply assuming that the surface charge densities adjust to keep the surface electrostatic potentials at a fixed value. Finally, I will describe the curious balance of electrostatic, chemical and entropic forces that leads to constant surface potentials and discuss implications for the structure and stability of systems with large numbers of particles. Week of Sep. 28, 2009 Wed. Sep. 30, 2009 4:00pm MR418N Colloquium [CM] Prof. Chandrasekhar Ramanathan, Massachusetts Institute of Technology Quantum control and simulation with solid state magnetic resonance techniques Abstract: Quantum Computing has attracted considerable attention recently. While a truly scalable quantum computer will probably not be realized for many years, there are a number of promising near-term applications that could benefit from recent advances in quantum control. Special purpose quantum sensors, for example, promise to attain the highest performance permitted by the laws of physics, while not requiring the capabilities of a general purpose quantum computer. The simulation of many-body quantum systems is another area where a limited degree of control could enable new experiments that yield insight into long-standing theoretical problems. Solid state magnetic resonance is a unique experimental platform for us to pursue these ideas. I will describe our efforts to experimentally probe quantum dynamics in large Hilbert spaces, combining recent advances in quantum control with the rich history of NMR and ESR techniques developed over the last 60 years. Week of Oct. 5, 2009 ----------------------------------------- Tues. Oct. 6, 2009 October is for Physics Majors 12:15 in Room MR417 Lunch 1:00 in Room MR417 Prof. Sergey Vitkalov, Physics Department, CCNY "Violation of Ohm's Law in transport of electrons with quantized spectrum" followed by laboratory tour. ------------------------------------------ Wed. Oct. 7, 2009 IUSL Speaker Series, 2:00 pm, Rm MR418N Prof. Enrique Galvez, Colgate University "The Helical Mode of Single Photons: Baby Steps Twoard Quantum Imaging" Abstract: I will present recent experiments that we have done that showed the helical mode of single photons. We do this via an interference experiment. Experiments are under way to study the correlations of two identical photons, or biphotons, in helical modes. Since images are made of fundamental modes a photon can carry the information of an entire image, a superposition of modes. We investigate the case where the image is carried by the two photons but not any one individually. The image also contains quantum-optical singularities, optical singularities that are non-classical. Dr. Enrique Galvez is currently a Professor of Physics at Colgate University in Hamilton New York. Professor Galvez is an atomic and optical physics experimentalist. Recently his studies have focused on optics and quantum optics. These include fundamental studies of the geometric phase in optics, optical beams in high-order modes, singular optics, photon entanglement and studies of quantum interference with correlated photons. Prof. Galvez is also interested in physics education and in the development of new physics laboratories for undergraduates. ------------------------------------------------ Wed. Oct. 7, 2009 Colloquium 4:00 pm Rm MR418N [DG] Noel Goddard, Hunter College, CUNY "Safety in Numbers" Abstract: Microbes utilize population strategies to manage error and acquire competitive advantage. I will discuss ongoing efforts to measure the error spectrum of the protein pool in bacteria, and its implications about the structure of the genetic code. Also I will discuss the measurement and modeling of the dynamics of genetic elements which enable phenotypic novelty. These elements are known to persist at abnormally high rates in natural microbial populations. We study this persistence and its relation to selection. ------------------------------------------ Thurs. Oct. 8, 2009 October is for Physics Majors 12:15 in Room MR417 Prof. Frederick Smith, Physics Department CCNY "Majoring in Physics: Opportunities" 1:00 in Room MR417 Prof. Richard Steinberg, School of Education and Physics Department, CCNY "Physics Education Research at CCNY" followed by laboratory tour. ------------------------------------------ Week of Oct. 12, 2009 Mon. Oct. 12, 2009 Columbus Day Holiday, College Closed ------------------------------------------ Tues. Oct. 13, 2009 October is for Physics Majors 12:15 in MR417 Prof. Daniel Greenberger "Causality, Bell's Theorem, and Entangled States in quantum theory" 1:00 in MR010 Mr. Jose Pinto, MA Student Planetarium Show "The Night Sky" (30 minute show, repeated on Thursday, October 15.) See the apparent motion of the celestial bodies from different points on earth. The Planetarium is in room MR010, in the basement. Take the south stairs from the Street Level. ------------------------------------------ Wed. Oct. 14, 2009 Monday Schedule Week of Oct. 19, 2009 ------------------------------------------ Tues. Oct. 20, 2009 October is for Physics Majors 12:15 in MR418N Poster presentations by Physics Majors and High School students from Academic and Summer 2009 Research. Followed by laboratory tours. ------------------------------------------ Wed. Oct. 21, 2009 4:00pm MR418N Colloquium [MPS] Professor Pallab Bhattacharya, University of Michigan "Spin-Polarized Quantum Dot Lasers and Single Photon Sources" For abstract and biographical information, please go to: http://mail.sci.ccny.cuny.edu/~physdept/Fall2009/102109Bhattacharya.pdf ----------------------------------------- Thurs. Oct. 22, 2009 October is for Physics Majors 12:15 in MR417 Prof. Mark Shattuck "Granular Equilibrium: Shaken not stirred" 1:00 in MR417 Prof. Ronald Koder "Protein design, synthetic biology and hybrid metamaterials at CCNY" Followed by laboratory tour. ----------------------------------------- Week of Oct. 26, 2009 ----------------------------------------- Tues. Oct. 27, 2009 October is for Physics Majors 12:15 in MR418N Prof. V. Parameswaran Nair "Quarks and Gluons: The surprise of a perfect liquid" 1:00 in MR418N Prof. Joel Gersten "Maxwell's Equations in a Suburban Setting" ----------------------------------------- Wed. Oct. 28, 2009 4:00pm MR418N Colloquium [DG] Ben Oppenheimer, American Museum of Natural History "Comparative exoplanetary science" Abstract: The study of planets orbiting other stars has been a hot topic in astronomy for some time now. The scientific questions that must be answered by this field are profound and simply fascinating, spanning astronomy, geology, atmospheric physics and perhaps eventually biology. Yet, we know so little about these planets because they are difficult to study spectroscopically. However, the limits on our abilities to study these "exoplanets" in detail are steadily being broken as several centers around the world work toward the highest contrast images ever made in any field of inquiry. I will describe our efforts at AMNH in exoplanet imaging and spectroscopy, while highlighting two of our main projects: an active search ongoing at Palomar, called Project 1640, and construction of the starlight suppression system for the Gemini Planet Imager. ------------------------------------------- Thurs. Oct. 29, 2009 October is for Physics Majors 12:15 in MR418N Dist. Prof. Myriam Sarachik "Research on Molecular Nanomagnets" Followed by laboratory tour. 1:00 in MR418N Mr. Ronald Schneider, B. S. Student and Physics Major "Investigating the Influence of Micro-structure on the Thermoelectric Efficiency of Bi0.52Sb1.48Te3". ------------------------------------------- Week of Nov. 2, 2009 Tues. Nov. 3, 2009 October is for Physics Majors 12:15 p.m. NAC Faculty Dining Room, 3rd Floor Due to a change in schedule, attendees are advised to proceed to the NAC Faculty Dining Room, 3rd Floor for the annual Student and Faculty Lunch. Presentations originally scheduled for today have been rescheduled: Prof. Marilyn Gunner: Tuesday, November 10 at 12:15 (see below) Dist. Prof. Robert Alfano: Tuesday, November 17 at 12:15 (see below) ------------------------------------------- Wed. Nov. 4, 2009 4:00pm MR418N Colloquium [DG] Greg Boutis, Brooklyn College, CUNY ""Average Hamiltonian theory and its applications to quadrupolar echo spectroscopy" Abstract: Average Hamiltonian theory, developed by J. S. Waugh, is a generalized control scheme for manipulating the coherent dynamics of quantum system. The method has been applied with great success in various facets of magnetic resonance including solid state NMR spectroscopy, solid state imaging and quantum computing. In this talk, I will give a very brief overview of some the advances average Hamiltonian theory has allowed for, and then describe some work we have performed in applying this control scheme to the NMR spectroscopy of quadrupolar spins in the solid state. Week of Nov. 9, 2009 Tues. Nov. 10, 2009 Presentation for Physics Majors 12:15 in MR418N Prof. Marilyn Gunner, CCNY Physics "Physics, Photosynthesis and the Sun" Followed by laboratory tour. -------------------------------------------- Wed. Nov. 11, 2009 4:00 pm MR418N Colloquium [MPS] (tentative) Vinod M. Menon,Laboratory for Nano and Micro Photonics, Department of Physics, City University of New York - Queens College & Graduate Center, New York, USA (Prof. Menon will be staying for dinner.) "DESIGNER PHOTONIC MATERIALS - FROM RESONANT PHOTONIC CRYSTALS TO FLEXIBLE PHOTONICS" Abstract: Coherent interaction of an ensemble of dipole active atoms or excitons with a vacuum electromagnetic field has been studied extensively since its initial conception by Dicke in 1954 [1]. However, when the emitters are not only periodically arranged, but are also placed in a periodically modulated dielectric environment, the interaction between them is carried by the electromagnetic Bloch waves of the photonic crystal. In this talk we will discuss our recent work on active photonic crystals where the excitonic absorption/emission is in resonance with the photonic crystal Bloch modes [2]. The formation of coherently coupled photonic-crystal-excitonic-lattice polaritons manifests in our experiments through enhanced reflectivity and reconstruction of the photonic bandgap. Tuning of these polariton states using electric field and its application for switching and slow light enhanced nonlinear optics will also be discussed. The collective nature of the hybrid excitations demonstrated here opens up the possibility of observing macroscopic coherence phenomena in solid-state systems. Following this we will briefly discuss our work on light emitters and photonic circuits realized using colloidal quantum dot composites. Specifically we will report our recent work on flexible microcavity lasers, active Fibonacci photonic quasicrystals, microdisk emitters and integrated active - passive waveguides. The effect of host matrix on the optical properties of the quantum dots will also be discussed using results of steady-state and time-resolved luminescence measurements. In addition to their specific functionalities, these novel device demonstrations and their development present a low cost alternative to the traditional photonic device fabrication techniques. Week of Nov. 16, 2009 Tues., Nov. 17, 2009 12:15 pm MR418N Presentation for Physics Majors Dist. Prof. Robert Alfano "Key to Ultrafast Physics" Wed. Nov. 18, 2009 4:00pm MR418N Colloquium [RK] Steve Greenbaum, Department of Physics & Astronomy, Hunter College of CUNY and CUNY Graduate Center Ph.D. Program in Physics "Multinuclear Solid State NMR Studies of Materials Related to Energy Conversion and Storage" (Prof. Greenbaum will be staying for dinner.) Abstract: Fundamental materials research is needed to move present-day energy storage technologies to the scale needed to develop all-electric vehicles and to manage intermittent sources such as wind and solar. Structural studies of materials utilized in lithium battery and fuel cell technology are often hampered by the lack of long-range order found only in well-defined crystalline phases. Powder x-ray diffraction yields only structural parameters that have been averaged over hundreds of lattice sites, and is unable to provide structural information about amorphous compounds. Our laboratory utilizes solid state nuclear magnetic resonance (NMR) methods to investigate structural and chemical aspects of lithium ion cathodes, anodes, electrolytes, interfaces and interphases. NMR is element- (nuclear-) specific and sensitive to small variations in the immediate environment of the ions being probed, for example Li+. NMR is also a powerful tool for probing ion and molecular motion in polymer electrolytes for lithium batteries and fuel cells (both hydrogen and direct methanol), with a dynamic range spanning some ten orders of magnitude through spin-lattice relaxation and self-diffusion measurements. A survey of brief summaries of several recent NMR investigations will be presented, including water and proton transport in nanocomposite PEM fuel cells membranes, single crystal studies of LiMPO4 (M = Fe, Co, Ni) cathodes, electrode passivation in lithium ion batteries, charge storage mechanism in carbon/MnO2 nanofoam electrodes, structural aspects of CFx primary lithium battery cathodes, and structural disorder in silicon alloy thermoelectric materials. Week of Nov. 23, 2009 Wed. Nov. 25 2009 4:00pm MR418N Colloquium Thu. Nov. 26 2009 Thanksgiving Holiday, College Closed Fri. Nov. 27 2009 Thanksgiving Holiday, College Closed Week of Nov. 30, 2009 Wed. Dec. 2, 2009 12:15 pm, MR418N Solid State Seminar [JLB] Prof. Vadim Oganesyan, Physics Dept., College of Staten Island, CUNY "Nernst effects" Abstract: After an overview of the recent renaissance of magnetothermoelectric (Ettingausen-Nernst) effect in high temperature superconductors and other correlated materials, I will compare and contrast three different theoretical approaches to this phenomenon: Boltzman kinetics, hydrodynamics and some very recent and exact results in "high" magnetic field. The latter applies to recent experiments in 3D semimetals, graphene and some semiconductors (e.g. HgTe:Fe). Wed. Dec. 2, 2009 4:00 pm MR418N Colloquium [MPS] Dr. Robert Willett, Alcatel-Lucent Title TBA Week of Dec. 7, 2009 Wed. Dec. 9, 2009 12:15 pm MR418N Solid State Seminar [JB, JFT] Dr. Alfred Q. R. Baron, Materials Dynamics Laboratory, SPring-8, RIKEN & High Resolution Inelastic X-Ray Scattering, Hyogo, Japan "Phonon Dispersion in Superconductors via Inelastic X-Ray Scattering:The Iron-Pnictide Materials." Abstract: High-resolution, non-resonant, inelastic x-ray scattering (IXS) is the modern method of probing phonon dispersion with meV resolution from ~microgram single crystals. We apply this technique to the new family of iron-pnictide high-temperature superconductors recently discovered by Hosono and coworkers [1], focusing on the “1111” family of materials, especially PrFeAsO1-y. This family has the highest Tc of the iron-pnictides, and we have measured samples having Tc 45K and <4K due to different oxygen concentations. Our measurements show significant discrepancies from ab-initio calculations, but do not show clear hallmarks of strong electron-phonon coupling, such as those present, for example, in the phonon spectra of MgB2. Detailed comparison of these results with several different ab-inito calculations shows the best fit to the measured data is for a model where magnetism has been included, despite the fact that the superconducting material does not show evidence of static magnetism. However, even then there are significant discrepancies between the calculation and the experimental results. The best agreement, so far, is obtained by making a drastic modification to the ab-inito magnetic model, which, interestingly, mirrors some aspects of recent spin-wave measurements. The talk will introduce high resolution IXS, discuss its application to superconductors, and then focus on the iron-pnictides. We will also mention some other applications and describe the new, next-generation, instrument, which will be constructed at SPring-8 and is expected to be the world-leading facility for these measurements. References for the work on the pnictides include [2,3] and a recent review of IXS can be found in [4]. [1] Y. Kamihara, T. Watanabe, M. Hirano, and H. Hosono, J. Am. Chem. Soc. 130, 3296 (2008). [2] T. Fukuda, A. Q. R. Baron, S. Shamoto, M. Ishikado, H. Nakamura, M. Machida, H. Uchiyama, S. Tsutsui, A. Iyo, H. Kito, J. Mizuki, M. Arai, H. Eisaki, and H. Hosono, Journal of the Physical Society of Japan (Letter) 77, 103715 (2008). [3] T. Fukuda, A. Q. R. Baron, H. Nakamura, M. Machida, H. Uchiyama, S. Shamoto, M. Ishikado, M. Arai, J. Mizuki, H. Eisaki, et al., To be published. [4] A.Q.R. Baron, Journal of The Spectroscopical Society of Japan, Vol. 58, #5 (2009), pp 205-214 (In Japanese) / arXiv (In English) Wed. Dec. 9, 2009 4:00pm MR418N Colloquium [VPN] Paul Sorensen, Brookhaven National Laboratory Title TBA Fri. Dec. 11, 2009 Last Day of Classes Week of Dec. 14, 2009 Mon. Dec. 14, 2009 Reading Day (No Classes, College Open) Tue. Dec. 15 - Mon Dec. 21, 2009 Final Exams Wed. Dec. 16, 2009 4:00pm MR418N Colloquium Week of Dec. 21, 2009 Mon. Dec. 21, 2009 Last day of final exams Thurs. Dec. 24, 2009 Holiday, College closed Fri. Dec. 25, 2009 Holiday, College closed Week of Dec. 28, 2009 Thurs. Dec. 31, 2009 Holiday, College closed Fri. Jan 1., 2010 Holiday, College closed ********************************************************************* Physics Department events resume in February, 2010. *********************************************************************