Neutrino experiments over the past ten years have conclusively observed neutrino flavor oscillations, indicating that neutrinos have non-zero masses. I will briefly describe the physics of neutrino oscillations, focusing on the experimental evidence from solar, reactor, atmospheric and accelerator neutrinos. I will then describe MiniBooNE, an experiment at Fermilab designed to confirm or rule out the LSND signal, which is the only oscillation observation that has yet to be independently confirmed. I will show the latest neutrino data from MiniBooNE, and the updated oscillation sensitivity based on the first year of data.

Significant efforts have been made over the last 20 years to study and change both the demographics of graduate student enrollment as well as undergraduate education in physics. Innovations have been made to improve minority representation in the sciences and student retention of introductory physics content. In nearly the same time period, the study of nonlinear and non-equilibrium physics has matured, increasingly producing interdisciplinary and multidisciplinary research and funding opportunities with scientific disciplines outside of physics. Tabletop experiments in nonlinear and non-equilibrium systems offer unique opportunities to involve undergraduates in journal-publishable research projects that can both enhance their understanding of physics and help address current problems in the recruitment of graduate students at programs across the country. I'll present results from a few such research projects pursued in my laboratory at the University of Kansas, explain the model used for the maturation of research projects, and discuss the student-outcomes associated with these efforts as well as the scientific advances being made by the research itself.

A brief survey is given on how the properties of materials at the nanoscale differ from their bulk counterparts. We envisage that future applications of nanostructures will focus on these differences in properties and one applications area where significant impact may be expected is in addressing the grand challenge of our energy future. This topic will be further developed.

Techniques and Algorithms developed originally in High Energy Physics have been applied to selected problems in genetics with interesting results.

A brief biased review of the biological importance of protein structure from a physics point of view will be given. Three such problems that yield to a physics-type analysis will be discussed:

(1) Mean Field Techniques used in detector track fitting algorithms have been extended and applied to the comparison of protein structures. The practical use of such comparisons in drug development, for example, will be discussed. This application requires a complete knowledge of the 3-D structure of proteins but unfortunately not all proteins can be crystallized to allow a standard measurement.

(2) The possibility of measuring the charge structure of isolated small structures using the proposed SLAC Free Electron Laser, the LCLS, will be outlined. This involves determining the orientation of each structure, and performing an inverse Fourier transform when only the magnitude of each image pattern is measurable. A new algorithm for accomplishing this reconstruction will be discussed.

(3) A novel method that can determine sequences (DNA for example) has been developed by Sean Ling of Brown University. The measurement yields the distances between consecutive instances of a given codon but not its absolute position nor its orientation along the DNA chain. The mathematical problem is to fit the measurements on all the different codons into the intermixed sequence.

Problems and Opportunities in this field for physicists will be discussed.

In the perennial search for new materials for optoelectronic devices, organic semiconductors have attracted much recent attention due to their ease of fabrication, light weight, mechanical flexibility, and low cost. I will discuss the physics of the optical properties of some of the most promising organic crystals, and recent advances in device development.

Colloidal assemblies are ideal model systems in which to study basic equilibrium and non-equilibrium phenomena relevant to a wide range of condensed matter systems. Additionally, there are a variety of technological applications for self-organizing colloid structures, including photonic band gap materials and patterned nanostructures. Here we study the statics and dynamics of colloids interacting with external fields. When the fields are used to create a periodic substrate, we find a variety of novel crystalline states that we term "colloidal molecular crystals." These have interesting multi-step melting transitions and can be used to realize a variety of canonical statistical mechanics models physically. When the substrate is dynamic, we show that novel dynamical phases arise and lead to ratchet effects, which can be used to create new types of logic gates and new fractionation techniques. Many of these results have recently been realized experimentally for colloids interacting with periodic optical arrays.

Driving a single particle through a system offers a powerful experimental probe of the nonequilibrium dynamics of a nanoscale medium. Due to recent technical advances, magnetic force microscopy (MFM) can be used to manipulate individual magnetic vortices in a superconductor. We propose an experiment to resolve the controversial issue of whether vortices can entangle like polymers by using an MFM tip to wind one vortex around another and create an artificially entangled vortex state. We also use simulations of local probes to explore other phenomena, including local melting transitions, diverging length scales at jamming transitions, and nonequilibrium ordering transitions.

We propose a teleportation scheme that relies only on single-photon measurements and Faraday rotation, for teleportation of many-qubit entangled states stored in the electron spins of a quantum dot system. The interaction between a photon and the two electron spins, via Faraday rotation in microcavities, establishes Greenberger-Horne-Zeilinger entanglement in the spin-photon-spin system. The appropriate single-qubit measurements, and the communication of two classical bits, produce teleportation. This scheme provides the essential link between spintronic and photonic quantum information devices by permitting quantum information to be exchanged between them.

Ionizing particle radiation is a prominent feature of the space environment. Its energy density is comparable to that in starlight and in the cosmic magnetic fields. The energies of these particles span more than 14 orders of magnitude from <10⁶ eV to >10²⁰ eV. Their presence has significant adverse effects on the electronics in space systems and they pose a hazard for astronauts. The radiation has several sources. There is a continuous flux of particles coming from our galaxy and beyond. These particles bring us a rare sample of matter from beyond our solar system that tells us about the sources of these particles and their journey though the Galaxy to us. Adding to these at lower energies are particles accelerated at our sun, in the heliosphere and at its boundary with the interstellar medium. They have their own unique origins and acceleration processes. These radiation sources all contribute to the radiation trapped by the Earth's magnetic field and the magnetic fields of the other planets. This talk will be a general survey of ionizing particle radiation in space including the latest results.

The Laser Interferometric Gravitational Wave Observatory (LIGO) is poised to open a new window on the universe - the detection of gravitational waves from distant large-scale astrophysical sources. Gravitational waves were predicted by Einstein almost 90 years ago but never been observed directly despite a number of experiments over the last 40 years. While there exists strong indirect evidence for gravitational waves, it is only with the construction of large-scale high precision interferometers that direct detection of gravitational waves is possible. Gravitational waves are miniscule dynamic strains applied to space-time by motion of massive astrophysical objects. A passing gravitational wave will expand and contract the distance between two mirrors ('test masses') in the arms of an interferometer. Direct observation of gravitational waves presents a formidable challenge, because the effect is expected to be infinitesimal, less than one part in 10^-22.

The astrophysical motivation for detecting gravitational waves is compelling. Unlike the visible sky, the gravitational wave 'sky' is completely unexplored. Potential gravitational wave sources include binary neutron star and black hole systems and pulsars. The LIGO detectors and its partner GEO600 in Europe have the sensitivity to observe gravitational waves not only in our own galaxy, but in neighboring galaxies, thus opening an absolutely unique window into these phenomena.

In the first part of the presentation, I will give an overview of gravitational waves - what they are and where they come from - and describe in general terms the techniques that gravitational wave astrophysicists use to hunt for them. In the second part of the presentation, I will describe the LIGO interferometers and present results from the first searches for gravitational waves by LIGO.

Understanding turbulence has been recognized as a fundamental problem of theoretical physics for over a century. Due to instabilities of the fluid motion, fluctuations in the velocity can never be ignored (‘the butterfly effect’). Viscosity and other effects casue a dissipation. The balancing of these two forces lead to a singular stochastic field theory. Ideas from modern mathematics (non-commutative geometry) originally developed to study quantum gravity allow us to derive a formula for the entropy for the turbulent fluctuations. We can explain some qualitative features (‘reverse cascade’) of two dimensional flow by maximizing this entropy. Some ideas on extending these ideas to three dimensional flows will also be described.

Organic solar cells have the potential to be high-efficiency, low-cost, lightweight, flexible, large area, renewable energy sources. Solar power conversion efficiencies as large as 5% have now been demonstrated in polymer photovoltaics. There still exist substantial room for improvement through the development of novel organic materials and approaches for processing them at the nanometer length scale. In this talk, I will first discuss some of the key issues that limit the efficiency of solar cells in general and organic solar cells in particular. I will then describe our approach towards resolving some of these issues: thermally-controlled interdiffusion of polymer-fullerene photovoltaic films to produce nanoscale concentration gradients for optimized charge-transfer and charge-transport efficiency.

The Sun is the source of energy that has created and preserved all life on earth. Not surprisingly, humanity has wondered about how the Sun shines - in lore, lyric, and literature, epitomized by the simple query of the child: "twinkle twinkle little star, how I wonder what you are?"

The question became a scientific puzzle only about 150 years ago. A series of brilliant ideas and experiments in the early 1900's sharpened the puzzle into a scientific crisis. The breakthrough came with Einstein's theory of the equivalence of mass and energy and the development of quantum mechanics in 1925. The amazing answer came a decade later with the birth of nuclear physics: energy from the fusion of atomic nuclei in the 15 million degree core of the Sun.

Is this idea really correct? The question could only be settled by experiment, but how does one "look into" the core of the Sun and verify the presence of the thermonuclear furnace there? The clue was that the same fusion reactions that power the Sun also emit neutrinos that interact so weakly with matter that they can escape the huge mass of the Sun. We can actually see the solar burning if we can detect these neutrinos.

Doing that in practice, however, is almost a science fiction adventure: Huge detectors nearly a thousand tons in mass must be placed, ironically for a device to see the Sun, in caverns miles underneath tall mountains. Amazingly, the experiments still worked and proved conclusively that the Sun is indeed powered by fusion reactions. But they did much more. They revealed stunning surprises in a different discipline - elementary particle physics, by basically rewriting it with new chapters on the neutrino itself.

The adventure continues today with new questions such as - why is there more matter in the universe than antimatter? - and - did the Sun always shine steadily or did it vary in ancient times and cause vast changes in weather on the earth a million years ago? Ingenious new solar neutrino experiments are being developed at Virginia Tech to answer these questions.

Our universe is fundamentally quantum mechanical, yet truly quantum behavior isn't easily observed. Understanding these limits of quantum behavior is critical to fields such as quantum computing and quantum control. We all know that the emergence of classicality has something to do with the size of the system (the scaled value of Planck's constant for the system). Recently we have begun to understood that this is also strongly dependent on the lack of isolation of the given system from the outside world (a phenomenon known as decoherence) as well as the nonlinear dynamics of the classical limit of the system. I will summarize recent work on these issues, in particular focusing on the result that for certain chaotic systems it is possible to combine these three effects into a single parameter quantifying the difference between the quantum and classical worlds.

The Belle experiment at the KEKB electron-positron colliding beam accelerator has produced a number of significant results in the studies of CP nonconservation, precise measurements of many of the parameters of the Standard Model of particle physics, and the discovery of new resonances.

I will summarize the highlights of the new results and discoveries that were announced by the Belle collaboration in 2005, and provide a brief outlook on the future of this experiment.

The discovery of neutrino oscillations in 1998 has spawned a golden age of neutrino physics. As we embark on a program of precision measurements to study the neutrino mixing matrix, the question of what is the value of the last unknown mixing angle, θ₁₃, plays a central role. Following a review of the theory and the current experimental state, this talk will focus on the role that reactor neutrinos will play in determining the value of the mixing parameter sin²2θ₁₃. The need for precision, the challenges to achieving that precision, and the solutions to those challenges will be discussed.

Molecular electronics is an active area of research with the goal of supplementing currently available Si based electronics in further miniaturization of electronic devices. An intriguing issue in molecular junctions is the role played by nuclear motions in the conduction process. Theoretical study of electron-phonon interaction has a long history. In biased current junctions this issue raises new points for consideration. The interpretation of electronics transport in molecular junctions has so far being done in the context of multi-channel scattering problem. The influence of the contact population as well as of the electronic subsystem on the phonon dynamics is disregarded in this case. A systematic framework for describing transport phenomena of many-particle systems is based on the nonequilibrium Green's function (NEGF) formalism. We use the NEGF he NEGF formalism to describe c electron transport through molecular junctions for weak and strong electron-phonon interactions.

The weak interaction case corresponds to non-resonant phonon assisted electron tunneling. Theoretically it can be described by a perturbation (in interaction strength) approach on the Keldysh contour. The lowest non-zero diagrams lead to self-consistent Born approximation (SCBA) for both electron and phonon Green functions. We use the scheme to describe features (peaks, dips, lineshapes and linewidths) observed in the IETS signal, d²I/dV² as function of the applied bias voltage V.

The strong electron-phonon interaction usually corresponds to the near resonant tunneling situation. Generally, perturbative consideration in this case breaks down. We investigate two possible approaches. One is based on the Born Oppenheimer approximation. The approach leads to a simple mean field model, which becomes exact in static limit. We apply the scheme to describe negative differential resistance (NDR) and hysteresis observed in molecular junctions within the same polaronic model. In the second approach we try to avoid timescale limitations. This approach is based on the second order cumulant expansion and equation of motion method. We propose a self-consistent scheme on the Keldysh contour to investigate intermediate to strong electron-phonon interaction parameter region. We apply the scheme to study inelastic resonant tunneling in molecular junction and compare our results to previous works.

Evidence of neutrino oscillations has been around for quite some time, in various forms. Recently our thinking has undergone a kind of revolution as pieces of the puzzle have come together in a consistent manner. It is now becoming possible to perform sensitive tests of fundamental parameters of neutrinos, and they have become more interesting the deeper we have looked. There are many experiments currently investigating neutrino properties, and many more ambitious ones planned, proposed and approved. In this talk I will discuss the evidence, theory, and some of the experiments in this increasingly interesting and developing field.

The universe is filled with matter. Our telescopes shower us with images of stars, nebula, galaxies and clusters of galaxies to the limits of our vision. But when we study the motion of this luminous matter and compare it to our expectation based on our knowledge of gravity, the calculations and observed quantities fail to agree. The evidence points to non-luminous matter, or dark matter, extending over larger distance scales than that of the luminous matter.

Big bang cosmology gives strong evidence for this dark matter to be massive, weakly interacting particles. If particle dark matter is present in the Milky Way it is possible to detect it in the laboratory. Detection strategies employ varied degrees of technical sophistication but most experiments to date have featured limited detector mass. Significant progress in the field -- discovery, particle property determination and astronomy -- is expected to arise from expanding detector mass towards the ton scale and perhaps beyond. This talk will broadly consider the search for dark matter and provide a framework for understanding why the dark matter issue is of central importance to astronomy, cosmology, and high energy physics.

Developing theories which bridge the gap between ab initio computables and experimental observables provides not only quantitative predictions but also new physical insights. This talk presents three such theories in the contexts of (1) two-gap superconductivity in magnesium diboride, (2) the contribution of reconstructions of the silicon divacancy to mechanical loss in mechanical resonators, and (3) understanding of experimental measurements of suspended nanotube resonators.

Computer simulations play a vital role in the design and interpretation of nanoscale experiments, since they extend and validate (and on occasion supersede) the predictions of simplified theoretical models. The accurate simulation of interacting electrons is always a challenge. At the nanometer scale this challenge grows: there is no longer a clear distinction between the device and leads, thermal and quantum fluctuations become important, and spin ordering and magnetic fields may dominate. We are advancing many-body path integral quantum Monte Carlo techniques to meet these challenges. I'll discuss three areas~ fixed phase algorithms, highly-acurate Coulomb propagators, and linear response theory~ where we are combining math, physics, and computing to develop powerful new tools for simulating semiconductor devices and molecular electronics.

Dynamical properties of systems which are quenched from the high-temperature phase to or below the critical point are the subject of intensive studies, both experimentally and theoretically. A key insight has been the observation that many of the apparently erratic and history-dependent properties of such systems can be organized in terms of a simple scaling picture. This means that there is a single time-dependent length-scale L(t) in the problem. Useful insight may often be gained via the consideration of simple ferromagnetic models (rather than genuinely glassy systems). In the first part of the talk I discuss the recent progress achieved in the study of the dynamical behaviour of ferromagnets far from equilibrium. I thereby focus on the kinetics of phase-ordering which takes place after a rapid quench from an initially disordered state into the ordered phase. In the second part of the talk I study various spin glasses quenched to their critical point. I show that far from equilibrium critical spin glasses display the same aging phenomenology as critical ferromagnets. Interestingly, the out-of-equilibrium simulations of spin glasses reveal an unexpected dependence of critical quantities on the choice of the distribution of the random couplings.

Neutrinos are weakly interacting particles that are produced copiously at the center of the Sun through the nuclear fusion processes taking place there. The detection of these solar neutrinos provides us with vital information on the source of the Sun's energy, and also on the properties of the neutrinos themselves.

During the past few decades, various experiments have been conducted to measure the solar neutrino flux, and they have led to several significant discoveries. In the early stages, it was found that the observed solar neutrino flux was significantly less than what was theoretically expected based on our understanding of the Sun. This was the so called 'solar neutrino problem'. More recent experiments, such as Super-Kamiokande, which I will describe in some detail, have been able to detect solar neutrinos with high statistics and precision. The combined results of these experiments proved that neutrino oscillation phenomena, which was proposed as a solution to the solar neutrino problem, were indeed occurring for the neutrinos from the Sun.

At present, several challenging solar neutrino experiments, such as the LENS experiment under development at Virginia Tech, are being actively proposed. More than 90% of the neutrinos generated by the nuclear fusion reactions inside the Sun are thought to be in the low energy region where they have so far eluded direct observation. Most of the efforts for future detector development is directed toward observing solar neutrinos in this lower energy region, so that we may better understand the mechanism of energy generation in the Sun.

Adaptation is ubiquitous in biological sensory systems. Specifically, precise adaptation allows bacteria such as Escherichia coli to efficiently chemotax, i.e. to swim up gradients of attractants such as amino acids or sugars. The adaptation mechanism relies on methylation and demethylation (or deamidation) of specific modification sites of the membrane-bound chemoreceptors by the enzymes CheR and CheB, respectively. These enzymes can assist modifying 5-7 nearby receptors when tethered to a particular receptor. Using a free-energy based model for signalling by clusters of chemoreceptors, we show that these ``assistance neighborhoods'' are necessary for precise adaptation. In agreement with experiment, clusters of receptors of different type exhibit high sensitivity and precise adaptation over a wide range of concentrations, and the response of adapted clusters to addition/removal of attractant scales with the free-energy change of the receptors. We predict two limits of precise adaptation at large attractant concentrations: either become fully methylated and turn off, or receptors become saturated and cease to respond to attractant, but retain their adapted activity.

Since the 1950's, physicists have used nuclear reactors to study the properties of antineutrinos. In 1956, one of the first such experiments, Project Poltergeist, proved the existence of antineutrinos. The initial experiments were only a few meters away from the reactor core, the source of electron antineutrinos. Over the years the experiments steadily increased their baselines, with the goal to test and ultimately establish neutrino disappearance. That goal was reached in 2002, when the KamLAND Collaboration, using a one kton liquid scintillator detector, reported the first observation of electron antineutrino disappearance from 53 Japanese reactors at an effective baseline of ~180 km. KamLAND has since observed distortions in the antineutrino energy spectrum, a telltale sign of neutrino oscillation. The experiment has also measured a key neutrino oscillation parameter, the solar mass-splitting, to unprecedented levels.

Reactors, however, are not the only source of antineutrinos on Earth. Radioactive decays in the Earth also produce antineutrinos and the heat released in that process may be the driving force for mantle convection, which is responsible for terrestrial phenomena such as earthquakes and plate tectonics. KamLAND can detect geologically produced electron antineutrinos from the U238 and Th237 decay chains. Earth composition models predict that these are responsible for the majority of the radiogenic heat; detection of geoneutrinos from these two decays will allow the models to be directly tested for the first time.

I will discuss how KamLAND's measurements have further solidified the case for neutrino oscillation and the exciting recent detection of geoneutrinos.

Biological polymers carry out their functions in living systems where the environment is very concentrated or crowded by macromolecules. The volume fraction of these macromolecules that include proteins, nucleic acids, lipid membranes, and cytoskeletons can be up to 40% or more. In other words, physically, the composition of a cell is more than "a sack of water"; its consistency is closer to Jell-O. Experiments suggests that, because of this macromolecular crowding effect that confines polymeric dynamics, the kinetics and thermodynamics of protein folding and the association rate constants of protein-protein interactions in a cell (in vivo) are very different from that in a diluted test tube (in vitro). In order to quantitatively understand macromolecular crowding and confinement effects on protein dynamics, we used coarsely-grained models that physically captured interactions between crowders and a protein. The folding rates of a model protein nonmonotonically increased with the volume fraction of the crowders. At lower volume fractions, depletion-induced attractions from crowders could be mapped according to the spherical confinement model. A result of spherical confinement was the destabilization of denatured states by disallowing extended configurations that were longer than the pore size. However, at higher volume fractions, conformational fluctuations of a protein were susceptible to the shape of the confining condition. Thus, an approximation of the spherical confinement to mimic crowding effects was no longer effective.

Physicists have uncovered many surprising properties of neutrinos, in particular their extremely small but non-zero masses and large amount of flavor mixing. However, many fundamental questions remain about their properties. Two of these are:

• Are neutrinos their own anti-particles?
• What are the absolute masses of neutrinos?

This talk will discuss the hypothetical process of neutrinoless double-beta decay, the only practical method that could determine if neutrinos are their own anti-particles. Neutrinoless double-beta decay could also provide a sensitive probe to the absolute neutrino mass scale. I will also provide a status update of searches for neutrinoless double-beta decay, with emphasis on the Majorana experiment, a proposed detector to search for the neutrinoless double beta decay of Germanium-76.

Spin glasses are the paradigms of disordered systems in statistical physics. Ideas derived from studying spin glasses have been applied to problems ranging from biological sequence analysis to hysteresis studies of magnetic recording media. However, concepts taken from the solution of the mean-field Sherrington-Kirkpatrick model for spin glasses, e.g. aging, ultrametricity, and the existence of the Almeida-Thouless line, remain to be understood for realistic short-range spin glasses. Because no analytic solutions exist for short-range systems, large-scale computer simulations are the tool of choice.

After presenting a brief overview of the properties of spin glasses, I discuss the existence of the Almeida-Thouless line, i.e. the existence of a spin-glass state in a field. By using a one-dimensional long-range Ising spin glass with tunable power-law interactions, we are able to scan the full range of possible behaviors from the infinite-range (Sherrington-Kirkpatrick) model to short-range spin glasses. This allows us to effectively study high-dimensional systems with large system sizes, a previously inaccessible regime. We find that for short-range Ising spin glasses, there is no Almeida-Thouless line away from the mean-field regime.

I will give a brief overview of modern work on string theory. Much of the talk will cover the appearance of extra dimensions in string theory, and how one can reconcile that with the real world. There are two prominent approaches, "braneworlds" and "compactifications," and I will outline both in turn, discussing possible experimental verifications of some features of each scenario as well as how data from observational cosmology is shaping current attempts to extract phenomenological predictions from string theory.

It has recently been discovered that incorporating Mn into the lattice of a III-V semiconductor (such as GaAs) will render the III-V semiconductors ferromagnetic. To ensure that the Mn concentration in the III-V lattice is sufficient to achieve this, such ferromagnetic III_1-xMn_xV alloys must, however, be formed by non-equilibrium crystal growth, whereby Mn concentrations x approaching 0.10 can be obtained. The ferromagnetism of these alloys occurs because Mn ions, in addition to providing magnetic moments, also act as acceptors, thus providing large concentrations of holes. The Curie temperatures (which are determined by both the Mn and the free carrier concentration) currently reach about 170 K. Major efforts are being made around the world to increase this value because of the possible applications of III_1-xMn_xV alloys in spin electronics, where the vision is to harness the spin degree of freedom of the electron -- in addition to its charge -- in order to achieve new multi-functional spin-electronic devices. But for such devices to be of practical importance, they must operate at room temperature. I will discuss the fundamental magnetic properties of these new ferromagnetic semiconductor materials; fundamental mechanisms which presently limit their Curie temperatures; various strategies to overcome this obstacle in order to achieve semiconductors that are ferromagnetic at room temperature; and why this would be important.

The study of protein folding - the self-assembly of a polypeptide chain into a specific, functional structure - remains an area of active interest for biologists, chemists, and physicists. Several advances in recent years have allowed a new focus on the fastest protein folding, which occurs on microsecond time scales: Chemists have gained the ability to design novel, ultrafast-folding molecules; Computational scientists have developed tools for simulating that folding in atomic detail; Experimentalists have constructed instruments that probe those fast reactions in the laboratory. I will give a physicist's overview of protein folding dynamics, with emphasis on those physical properties of polypeptide chains that ultimately control the kinetics and dynamics of this critically important biological phenomenon.

Single-walled carbon nanotubes (SWNTs), tubular crystals of sp² -bonded carbon atoms that are just one atom thick, are one of the most exotic 1-D systems available today, possessing unique electronic, mechanical, optical, and magnetic properties. This talk will describe our recent high-field magneto-optical studies on SWNTs, which confirm theoretical predictions that the band structure and excitonic properties of a SWNT have unusual dependence on the magnetic flux φ, threading the tube, which breaks the time-reversal symmetry. We observed field-induced optical anisotropy as well as red shifts and splittings of absorption and photoluminescence peaks [1]. The amounts of shifts and splittings depended on the value of φ/φ₀( φ₀ = h/e: magnetic flux quantum) and are quantitatively consistent with theories based on the Aharonov-Bohm effect [2,3]. This represents the first evidence of the influence of the Aharonov-Bohm phase on the band gap of a solid. Furthermore, to gain insight into the internal energy structure and radiative properties of excitons in SWNTs, we systematically studied photoluminescence in pre-aligned film samples as a function of magnetic field and temperature [4]. The intensity of photoluminescence increased, or "brightened," with magnetic field and the amount of brightening decreased with temperature. These results can be explained in terms of a dark exciton state below the first bright exciton state [5]. Magnetic flux removes valley degeneracy by lifting the time-reversal symmetry and produces two equally-bright states at high magnetic fields [6]. I will discuss the mechanism of magnetic brightening by taking into account magnetic-field-dependent effective masses, populations of finite-momentum exciton states, and acoustic phonon scattering.

References

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