College of Arts and Sciences

Continue reading… Michelson Postdoctoral Prize lecture – Adam Bolton

How to Efficiently Convert Electrical Energy into Light Using Organic Materials

Continue reading… How to Efficiently Convert Electrical Energy into Light Using Organic Materials – Zakya H. Kafafi

I shall describe what the field looked like when I entered it as a foot-soldier, i.e. research student, more than half a century ago: what was known, who knew it and looked for more, how they did it. I shall illustrate with examples from my experience and observation. To see where we were then is to realize how far we have come and how the community and its customs have changed.

Continue reading… Low Temperature Physics and Physicists Six Decades Ago – B. S. Chandrasekhar

In 1933 Dayton Miller published the results of his voluminous observations using his ether drift interferometer, and proclaimed that he had determined the “absolute motion of the earth”. This result is in direct conflict with the prediction of Special Relativity, and also with numerous related experiments that found no such signal or “absolute motion”. I will present a complete explanation for his anomalous result by: a) showing that his results are not statistically significant, b) describing in detail how flaws in his analysis procedure produced a false signal with precisely the properties he expected, and c) presenting a quantitative model of his systematic drift that shows there is no real signal in his data.

Continue reading… An Explanation for Dayton Miller’s Anomalous “Ether Drift” Result – Tom Roberts

All around us things seem to get jammed. Before breakfast, coffee grounds and cereal jam as they refuse to flow into our filters and bowls. On the way to work, we are caught in traffic jams. In factories, powders jam as they clog in the conduits that were designed to have them flow smoothly from one side of the factory floor to the other. Our recourse in all these situations is to pound on our containers, dashboards and conduits until the jam miraculously disappears. We are usually so irritated by the jam that we do not notice that the approach to jamming and the jammed state,

Continue reading… Jamming – Andrea Liu

A new window in astronomy will open once gravitational-wave interferometers detect “first light.” These detectors will give us a revolutionary view of the Universe, complementary to the electromagnetic perspective. The detection and characterization of gravitational waves is a formidable undertaking, requiring innovative engineering, powerful data analysis tools as well as careful theoretical and numerical modeling. Binary black holes are expected to be one of the primary sources of gravitational radiation. I will review the latest developments to numerically model binary black holes. I will also address the role that these simulations have of assisting us in exploring where and how gravitational wave observations can enhance our understanding of astronomical phenomena and gravity.

Continue reading… Binary black holes and their echoes in the Universe – Pablo Laguna

The recent observation that certain metallic nanoparticles possess plasmon resonances that depend very sensitively on the shape of the nanostructure has led us to a fundamentally new understanding of the plasmon resonances supported by metals of various geometries. This picture- “plasmon hybridization”, reveals that the collective electronic resonances in metallic nanostructures are mesoscopic analogs of the wave functions of simple atoms and molecules, interacting in a manner that is analogous to hybridization in molecular orbital theory. The plasmon hybridization picture can be applied to an entire family of plasmonic nanostructures of various geometries, such as spherical shells, or ÒnanoshellsÓ, offset shells,

Continue reading… Plasmons in metallic nanostructures – Peter Nordlander

Continue reading… 2007 Distinguished Lecture: Warped Passages: Unraveling the Mysteries of the Universe’s Hidden Dimensions

Producing nanometer-scale architectures on surfaces is a current technological and scientific challenge. A natural alternative to current fabrication methods is the self-assembly approach, which allows atomic and molecular building blocks to organize themselves into useful nanostructures and is a fundamental principle for growth in all living organisms. I will present our recent results of self-assembled supramolecular networks at surfaces, stabilized by non-covalent interactions. By selection of molecular building blocks with specific properties, we can “program” these systems to pattern a surface with homogenous networks of specific size, structure, and physical and chemical properties.

Continue reading… Self-assembled Molecular Nanostructures at Surfaces – Steven Tait

Molecular-scale devices hold the potential for a wide range of electronic applications requiring new fundamental scientific understanding.ÊOne of the biggest challenges in developing molecular-scale devices is to fabricate precisely and monitor the formation of the nanometer-scale electrodes.ÊWe have developed a technique that employs an applied current with feedback for controllably electromigrating a nano-scale electrode down to the quantum regime.ÊThe technique permits high-resolution imaging in a transmission electron microscope, which shouldhave far reaching applications in the design and study of these extremely small devices.

Continue reading… Controlled Fabrication and Imaging of Nano-Scale Devices – Douglas Strachan

Nanowire field effect transistors (NWFETs) are emerging as powerful sensors for bio-molecule detection. I will discuss the interplay of device parameters such as gate bias and NW diameter on the sensitivity of NWFET sensors. Based on a fundamental understanding of the device physics, we demonstrate greatly improved sensitivity in both pH and cancer marker protein detections by operating the NWFET in the subthreshold regime where carriers in nanowire have reduced screening ability.

Continue reading… The Sensitivity Limits of Nanowire Bio-Sensors – Xuan Gao

Junctions between p and n type semiconductors are the fundamental structure upon which nearly all semiconductor technology is based. The stabilization of such junctions within a solution-processed semiconductor has great potential in the continuing expansion of organic electronic and/or photonic devices. We describe a process for forming fixed polymer homojunctions that demonstrate stability and high rectification ratios. This method shows promise beyond light-emitting displays for a range of device architectures for rectification, amplification, and photovoltaic applications.

Continue reading… Optoelectronic devices based on a semiconducting polymer homojunction – Janelle Leger

Transition metal oxides constitute a prototype for complex electron systems in which electrons organize collectively and give raise to spectacular macroscopic properties, with the most prominent examples being high temperature superconductivity and colossal magnetoresistance. The study of these systems has to date unveil a common motif which is becoming a paradigm in condensed matter physics: the interplay and competition of multiple degrees of freedom like charge, lattice and spin. In this talk, I will provide a compelling example of this paradigm by discussing the results of some recent angle-resolved photoemission spectroscopy (ARPES) investigations in the prototypical colossal magnetoresistive compound La1.2Sr1.8Mn2O7.

Continue reading… Colossal magnetoresistive manganites and high temperature superconductors: so different, yet so similar – Norman Mannella

April 25th, 2003, marked the 50th anniversary of the publication, in Nature (171:737-738, 1953), of the paper by James D. Watson and Francis H. C. Crick describing the double-helical structure of DNA. While some would date the beginning of molecular biology to this paper, it is not difficult to find antecedent developments, experimental and conceptual, that point in the same direction. One such event that contributed to the origins of molecular biology is the lecture, “Light and Life,” delivered by Niels Bohr in Copenhagen on August 15, 1932. In this lecture, the text of which was later published in Nature (131:421-423,

Continue reading… Bohr’s Vision, Delbruck’s Quest, and the Ironic Origins of Molecular Biology – Neil Greenspan

We performed conductivity measurements of the 2D Wigner solid, which is an triangular array of electrons, on the surface of superfluid He-A and B phases under magnetic fields. The He-A phase has a nodal point of energy gap at North and South Poles of the Fermi sphere and is anisotropic. A unit vector directing from the South Pole to the North Pole is refered to as the L vector. Spatial orientational effect of the L vector is called a “texture”. The L vector preferentially aligns parallel to a surface normal. The conductivity of the Wigner solid is sensitive to the quasiparticle distribution,

Continue reading… Surface texture in the A and B phases of superfluid He-3 probed by surface state electrons – Kimitoshi Kono

I’ll talk about how music theorists encounter structures familiar from physics — symmetry groups, eigenvectors, gravitational fields, even — believe it or not — local U(1) gauge invariance.

Continue reading… Music Theory and Physics – Dmitri Tymoczko

All evidence for dark energy is indirect (as is the evidence for acceleration of the universe). In this colloquium I will discuss different approaches for interpreting the data usually said to be evidence for dark energy.

Continue reading… Dark Energy: Taking Sides on the Issue [Joint Colloquium with Astronomy] – Rocky Kolb

Current experimental efforts are clarifying quite beautifully the nature of charge transport in so-called molecular junctions, in which a single molecule provides the channel for current flow between two electrodes. The theoretical modeling of such structures is challenging, because of the uncertainty of geometry, the nonequilibrium nature of the process, and the variety of available mechanisms. The talk will center on the first formulation of the problem in terms of scattering theory, and then on the generalizations needed to make that simple picture relevant to the real experimental situation. These include vibronic coupling, structural disorder and dephasing . Calculations of inelastic tunneling spectra,

Continue reading… Electronic Motion in Molecular Circuits: Elastic Scattering and Beyond – Mark Ratner

Light propagation in negative index materials (NIMs) is most unusual: light wave and energy travel in opposite directions. NIMs open the door to fundamentally new optical phenomena, and offer enormous potential for new device applications. Much of the current effort in this rapidly advancing field is aimed at realizing materials with a negative index at optical frequencies, where the wavelengths are five orders or magnitude smaller than in the microwave regime where negative refractive indices were first demonstrated. NIMs do not exist in nature; they must be man made. Since characteristic lengths need to be on the nanometer scale, nanoparticles are ideal building blocks for NIMs.

Continue reading… Nanoparticle Liquid Crystals as Negative Index Materials – Peter Palffy-Muhoray

After a brief overview of recent achievements at the National High Magnetic Field Laboratory (MagLab) using our pulsed, powered, and persistent magnets, I will focus on a series of my own experiments that utilized 60T pulsed magnetic fields to suppress the superconducting state in the high-temperature superconductors. The pulsed magnets are operated to the point of catastrophic stress failure…and occasionally, inadvertently, beyond. Oddly, however, they seem to offer the gentlest way to reveal the low-temperature normal-state of the cuprates in the absence of superconductivity. Evidence from resistivity measurements suggests a metal-insulator transition underlying the superconducting state. More recently [Nature 424,

Continue reading… The Cusp at Optimum Doping in the Low-Temperature Hall Number of the High-Temperature Superconductors – Greg Boebinger

Ellen:Motivated by a desire to assert the quality of his medium through gesture and materiality, Jackson Pollock’s allover paintings appear to stem from undirected manic motor activity, belying the extreme control of process which actually generated their abstract imagery. Moving far beyond traditional notions of subject or theme, Pollock created poured compositions in which the physical tracks of his bodily movements are permanently indexed. In his own words, Pollock’s goal was to express the “experience” of the modern age: “not an illustration of, but the equivalent.” Working directly with dripping fluid paint provided the key to his breakthrough achievement: an immediate statement of unconscious energy.

Continue reading… Pollock’s Paintings: Are They Really Fractal? – Ellen Landau and Kate Jones-Smith

The personal realization that physics is fun and addicting began with a chain of accidental discoveries: discovery of physics as a non-academic profession, discovery of engineering physics, discovery of solid state and gaseous electronics, discovery of the management trap, and discovery of independent free-enterprise startups. Then the odyssey as a physics entrepreneur began. How easily a creative core of physicists formed an independent center of excellence doing what is fun in physics, but generating spin-off technologies and companies in the process, will be described along with the rules and strategies that perpetuated the fun for 25 years (plus 10 more years to date).

Continue reading… Physics is Fun — Odyssey of a Physics Entrepreneur – Ned Rasor

Magnetic levitation techniques, whereby a strong magnetic field gradient partially or completely counteracts the Earth’s gravitational force, are applied to a variety of fluids problems.Ê Static properties are studied as a function of the effective gravitational force, and dynamic behavior is investigated by varying the magnet current temporally over time scales as fast as tens of milliseconds.Ê Results for the stability, collapse dynamics, and resonance behavior of liquid bridges in air will be presented.Ê Additionally, results on gravitationally-driven fluid interface instabilities will be discussed, showing how this technique facilitates measurements in regions of parameter space that are not possible using extant methods.

Continue reading… Dancing Fluids in Controlled Gravity – Charles Rosenblatt

It is a widely held view among cosmologists that our standard theory of cosmology — inflationary Lambda Cold Dark Matter — is so successful that cosmology now consists almost entirely of determining the parameters of the standard model to greater and greater accuracy. I will discuss how, at least on the largest scales, this is patently false. The fluctuations that we observe in the cosmic microwave background at the largest scale are far lower in amplitude than those predicted by our model. Furthermore, the little that there is aligns itself in bizarre ways, including aligning with the geometry of the solar system.

Continue reading… Is the Universe Out of Tune? – Glenn Starkman

The new worldview that has emerged from recent developments in cosmology suggests that remote parts of the universe are in the state of explosive, accelerated expansion, called “inflation”. “Normal” regions, where inflation has ended, form islands in the ever-inflating sea. These “island universes” have a wide variety of physical properties and are constantly being produced. I will discuss the origin of the new worldview, its observational tests, and its bizarre implications.

Continue reading… Many worlds in one – Alex Vilenkin

One of the most vexing problems associated with nuclear energy is the inability to find a technically and politically viable solution for the disposal of long-lived radioactive waste. The U.S. plan to develop a geologic repository for spent nuclear fuel at Yucca Mountain in Nevada is in jeopardy, as a result of managerial incompetence, political opposition and regulatory standards that may be impossible to meet. As a result, there is growing interest in technologies that are claimed to have the potential to drastically reduce the amount of waste that would require geologic burial and the length of time that the waste would require containment.

Continue reading… “Recycling” Nuclear Power Plant Waste: Technical Difficulties and Proliferation Concerns – Ed Lyman

Richard Feynman gave a classic talk in 1959 envisioning the field of nanotechnology and inviting people to enter a new field of physics. Now, nearly 50 years later, we shall look at the issues and ideas that he presented and see how far we have moved toward his vision.

Continue reading… There is plenty of room at the bottom – Norman Tien