A new research area is probe-based microscopy. Both the Atomic Force Microscope (AFM) and the apertureless near-field optical microscope (ANSOM) make extensive use of the optical and scanning skills developed in the research of photothermal phenomena. Ongoing research includes both theoretical and experimental aspects of nanoelasticity studies and light concentration on a mesoscopic scale.
This research group utilizes infrared and visible optical techniques, that are applied to problems involving optical absorption, and the diffusive scattering of both thermal and photon density waves. These experiments involve imaging subsurface structures with industrial and medical applications, as well as the quantitative characterization of the thermal and optical properties of materials. The group pioneered both the theory and the experimental technique of thermal wave imaging. This imaging technique uses time-varying heat sources, together with synchronous surface temperature detection, to carry out sub-surface material characterization and imaging. Nine patents have resulted, several of which have been licensed, and a successful local company was formed to utilize and market the technology. The group has elucidated the theory of thermal wave scattering, with confirming experimental work, leading to fourteen Ph.D. dissertations since 1981. During this period, the research has received funding from the Army, the Air Force, the Navy, the FAA, and numerous companies.
An important recent application of the group's research has been the development of one-sided thermal wave measurements of the thickness of materials. The motivation of this work was to provide a basis for the development of practical tools for finding and quantifying defects in metals and composite materials, and for process control applications in automotive and aerospace industries. The research resulted in the development of algorithms for quantitative thermal wave defect depth and thickness measurements. An imaging system using these algorithms is now being evaluated by Boeing and the FAA as an alternative to conventional inspection techniques for detection and measurement of corrosion and disbonds in aging aircraft. These algorithms are currently in use by the US Air Force in Georgia for inspecting F-15's, C-130's and C-141's, and in Oklahoma City for inspecting KC-135's and B-52's, and by Nordam in Tulsa, to inspect composite structures in commercial aircraft.
Experimental equipment used by the group includes several Ar-ion lasers (up to 20 W), a CO/CO2 laser, 2 Nd/YAG lasers, a 16-W diode laser with a fiber optic delivery system, a number of high pointing stability probe lasers, and six high quantum efficiency InSb focal-plane-array IR imaging systems.
Positrons, being the antiparticles of electrons, are rather unique projectile particles for investigating interactions with regular matter due to the their ultimate destruction by direct annihilation into two 511 keV gamma rays or via forming positronium (Ps, an unstable hydrogen-like atom composed of a positron and an electron), which in turn annihilates into two 511 keV gamma-rays or three gamma-rays adding to 1022 keV. Astrophysicists have observed positron annihilation gamma-rays coming from solar flares, the direction towards the center of our Galaxy and other gamma ray bursting sources in our Universe, while medicine has developed PET (positron emission tomography) scanners for investigating the heart, brain, and cancerous tumors. Other uses of positrons are to study atoms, molecules, surfaces, and solids in fundamental research. Ps is an intriguing projectile because it is a neutral particle and has a finite lifetime ending in annihilation.
Our research group uses low energy (up to a few 100 eV) positron beams obtained from a sodium-22 radioactive source to investigate positron scattering from a variety of atoms and simple molecules in three different experimental systems. Our group is focused on measuring cross sections for total scattering using a beam transmission technique, differential elastic scattering using a crossed-beam approach, and Ps formation by observing the annihilation gamma rays from its decay. These measurements are providing evidence that coupling effects between the various scattering channels (e.g. elastic, Ps formation, and atomic excitation) are playing an important role in positron-atom (molecule) scattering. We are finding evidence that capture of electrons from inner subshells of atoms and from inner orbitals of molecules play a role in Ps formation. Most recently we have developed a new type of spectroscopy where we measure the ratio of 3 gamma to 2 gamma annihilation from Ps decay, which enables us to not only make detailed studies of Ps formation, but also the destruction of Ps as it interacts with a surface.
This research is supported by the National Science Foundation.
Recent Publications: "Measurements of positronium formation cross sections in positron-Mg collisions", E. Surdutovich, M. Harte, W. Kauppila, C. Kwan, T. Stein, Phys. Rev. A 68, 022709 (2003).
"Investigations of positronium formation and destruction using 3gamma/2gamma annihilation ratio measurements", W. Kauppila, E. Miller, H. Mohamed, K. Pipinos, T. Stein, E. Surdutovich, Phys. Rev. Lett. 93, 113401 (2004).
Soft materials such as polymers, colloids, membranes, liquid crystals comprise almost all materials of our everyday life, including life itself. They are neither simple liquids, nor crystalline solids and many of the fascinating and useful properties of these materials result from thermal fluctuations in the local nanoenvironment. Within the last few years, this has become an exciting example of an emerging, interdisciplinary field of science drawing upon physicists, chemists, biologists, chemical engineers and materials scientists. The goal of our laboratory is to conduct fundamental research in the field of soft materials by developing spectroscopy techniques, which can offer structural and dynamical information with unprecedented spatial and temporal resolution, down to the atomic and molecular scale. The laboratory uses two main experimental approaches: (i) Infrared spectroscopic ellipsometry, which can describe the identity, composition, molecular interaction and orientation of the various parts of the molecules, as well as the thickness of the adsorbed film in the same measurement of the same sampling area. (ii) Fluorescence correlation spectroscopy using which the rate of dynamic processes such as diffusion, aggregation and chemical reactions can be inferred from the fluorescence-intensity autocorrelation function. The single-molecule sensitivity of this technique allows complementing, ensemble-averaged rate measurements of traditional methods of physical analysis with the distribution around the average. This is important to understand the issue of heterogeneities in soft matter systems. We are interested in a broad agenda of research problems including (i) micro- and nanofluidics with complex fluids (ii) single-molecule diffusion in confined fluids (iii) interfacial behavior of fluids at soft surfaces and (iv) direct visualization of molecules during spreading.
At the core of our research is the development and application of novel Atomic Force Microscopy (AFM) techniques. AFM is a powerful tool for measuring and imaging forces at the atomic scale. It can be used in any environment, including liquids, and has applications in surface physics, nanotechnology, materials science, chemistry, and biology. However, not all AFM's are created equal, and in our laboratory we focus on the application and further development of a novel AFM technique, which is optimized for quantitative local measurements of nanomechanical phenomena. This is achieved by using a dynamic measurement method in which the cantilever is oscillated at ultra-small amplitudes of less than 1 Ångstrom and monitoring changes in this amplitude as the surface is approached or the lever is scanned across the surface. Such a small amplitude allows to perform linear and local measurements of force gradients and forces. To measure changes in such a tiny amplitude we use a highly sensitive, optical fiber interferometer mounted to a sub-micron resolution manipulator. The interferometer can achieve several 100 mV signal per 1 Ångstrom deflection and can measure amplitude changes that correspond to a few hundredth of the diameter of a single hydrogen atom. Using such a small amplitude enables us to completely map any interaction point-by-point and achieve atomic resolution force gradient images at fixed separations. While we operate one instrument in ultra-high vacuum (UHV) for atomic resolution work, our technique also works well in liquids. We have recently build a new small-amplitude AFM operating in liquids. Interactions we have measured include bonding between single atoms (in UHV) and ordering of water molecules in a confined geometry (in liquid). We can also measure currents, charges and fields at the molecular/ atomic scale as well as atomic scale energy dissipation and molecular shear forces in liquids. Future and current research includes measuring forces during room temperature atomic manipulation, forces and currents associated with electronic/magnetic nanostructures, forces, structure and synamics in confined liquids, and forces associated with in biological macromolecules such as lipids and proteins.
My research primarily involves an experimental investigation of the electrical and magnetic properties of metals. Studies have been conducted on pure metals, alloys, and different types of thin magnetic films such as single-layer, bilayer, sandwich, and multilayer samples. The investigation of magnetic films has been carried out in collaboration with Prof. R. Naik in the Department and colleagues at Nanjing University. My studies often make use of low temperatures (down to 1 Kelvin), strong magnetic fields (up to 20 Tesla), and microwaves (up to 80 GHz in frequency). A rather unique piece of equipment used in the lab is a Millimeter Microwave Transmission Spectrometer operating at the highest frequency and sensitivity to be found anywhere in the world. Our studies provide a wealth of information on conduction-electron characteristics and magnetic interactions, which are valuable both for the fundamental knowledge they provide as well as for potential applications for devices.
The modification in surface properties of solids due to interaction of energetic ions (charged particles) is investigated using sputtering (r.f. and d.c.) and ion implantation (100 kV Varian Extrion) facilities. Ion backscattering and channeling analysis is carried out using the department's 4.75 MV Van de Graaff accelerator. An ultra high vacuum facility for low energy ion beam analysis coupled to the existing ion channeling analysis facility is under development. Current experiments involve ion beam induced dynamic mixing and ion channeling studies of an electrode-electrolyte interface. Some of the experiments are carried out in collaboration with General Motors Research Laboratory and other local industries.
When dealing with large organic molecules one frequently finds that there are several stable phases between the solid and liquid. Our research uses a combined theoretical and experimental approach towards the elucidation of the structures of these liquid crystalline mesophases and their physical properties. We are particularly interested in investigating the critical phenomena associated with the phase transitions between these various phases. One main focus of our work is on the role that chirality (optical activity) plays in producing structures and phase transitions. Experimentally we use various optical probes such as polarization microscopy, interferometry, and laser light scattering, including photon correlation spectroscopy. Theoretically we work with the phenomenological Landau theory of phase transitions. In recent years we have studied: (1) chiral smectic phases, which display ferroelectric and antiferroelectric behavior; (2) lyotropic nematic phases formed by mixtures of water with detergents; (3) organometallic mesogens, a new class of liquid crystals having both magnetic and conducting properties; and (4) cholesteric blue phases, some of the most exotic structures found in condensed matter physics, whose complexity derives entirely from their strong chirality.
Our research program in magnetic materials focuses on the fabrication and property characterization of magnetic nanoparticles, thin films, multiferroics, magnetodielectrics, and the development of these materials for device and sensor applications. Of particular interest are studies of domain structures in single-layered ferromagnetic thin films, multilayer structures exhibiting giant magnetoresistance, spin-polarized magnetic tunnel junctions, and hybrid semiconductor/ferromagnetic devices. Characterizations are primarily focused on transport (magnetoresistance and I-V characteristics) and magnetic (SQUID magnetometry, vibrating sample magnetometry, ac susceptometry, and ferromagnetic resonance) measurements between liquid helium and room temperature. Additionally magnetic force microscopy is utilized to determine the local magnetic structures of sub micron-size features and a point conductance technique based on the Andreev reflection of electrons has been developed for measuring the spin polarization of ferromagnetic materials. Magnetic films and devices are fabricated by molecular beam epitaxy (MBE), electron-beam, and sputter deposition systems.This program also makes extensive use of the facilities and research collaborations associated with the interdisciplinary Smart Sensor and Integrated Microsystems program.
Specific research projects include:
Spin Polarization Mapping (Nadgorny)
This research focuses on the implementation of nanoscale spin polarization measurements
utilizing Micro Electro Mechanical Systems (MEMS) positioning technology in combination
with electroforming of three-dimensional (3D) microstructures. A simple new technique of
electrodeposited (ED) photoresists makes possible conformal coatings of highly structured
surfaces and, when combined with electroplating, can form new types of advanced 3D metal
microstructures. By developing an array of micro-tips integrated with through-wafer
interconnects into a single testing chip, individually addressable m x n arrays of
microscopic superconducting tips on a testing chip can be fabricated. Then this testing
chip will be applied to thin films and planar magnetic nanostructures to map the spin
polarization over a larger cross-section and will allow non-destructive device evaluation
at any stage of the device fabrication. Furthermore, since both electrodeposition and
electroplating processes have the ability of forming complex topographies, this technique
has the potential to develop other 3D metallic microstructures for other potential
applications.
Multiferroics and Magnetodielectrics (Lawes)
Materials exhibiting simultaneous magnetic and ferroelectric order (multiferroics) are particularly interesting systems in which to investigate spin-charge coupling. Recently, in certain classes of multiferroic materials, it has been established that ferroelectricity is induced by the magnetic structure. These systems show very strong magnetoelectric coupling, to the extent that in some cases the spontaneous polarization can be switched by an external magnetic field. Understanding the properties of these multiferroics is crucial for incorporating these materials into novel magnetoelectric devices. Beyond single-phase multiferroics, various nanocomposite materials can also show substantial magnetodielectric effects. Magnetic nanoparticles embedded in an insulating matrix have been observed to exhibit a magnetization dependent dielectric constant. These composite materials may offer more versatility for device design than the single-phase multiferroic materials.
Magnetic Nanoparticles (Lawes and Naik)
This research project focuses on synthesizing and characterizing the properties of magnetic oxide nanoparticles, which typically range from 3 nm to 15 nm in diameter. In order to investigate how the magnetism of materials changes on the nanoscale, extensive studies of the magnetic properties of these systems are correlated with detailed measurements on their structure. One particularly intriguing problem focuses on understanding the role of interparticle interactions in determining the magnetic properties of these materials. Magnetic nanoparticles may also be important for biomedical applications. One system under extensive investigation at Wayne State is g-Fe2O3 nanoparticles in an alginate matrix, which is being studied for applications in targeted drug delivery, as an MRI contrast agent, and for hyperthermic treatments of malignant tumors.
This interdisciplinary research program involves the study of various thin film materials for potential magnetic, pyroelectric, piezoelectric, and chemical sensor applications. Materials of prime interest are ferromagnetic multilayered structures, ferroelectric thin films, wide bandgap semiconducting (III-V) nitride films, and other oxide thin films. Plasma Source Molecular beam epitaxy (PSMBE), MBE, sputter deposition, and metallorganic decomposition (MOD) methods are used to fabricate these thin film materials and devices. Microstructural characterization is done using one or more of the following methods: in situ reflection high-energy electron diffraction (RHEED), X-ray diffraction, Raman spectroscopy, auger electron spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Our magnetic characterization laboratories include SQUID magnetometry, magnetoresistance (MR), ferromagnetic resonance (FMR), atomic force micrsoscopy (AFM), and magnetic force microscopy (MFM) measurement capabilities. Electrical property measurements include both temperature and frequency dependent C-V, I-V, and impedance capabilities. This program is part of the interdisciplinary Smart Sensor and Integrated Microsystems program for developing magnetoresistive and magnetostrictive materials for magnetic sensor applications, oxide thin films for gas sensors, graded ferroelectric thin films for IR sensors, and wide band gap semiconductors for high temperature applications.
This research focuses on experimental and theoretical studies of Josephson effects and properties of high-temperature cuprate oxide and conventional superconductors. Present experimental programs include (1) studies of various physical phenomena such as the paramagnetic Meissner effect and intrinsic Josephson coupling in layered superconducting materials through electrical, magnetic, and electrodynamic measurements, (2) the fabrication and development of high-temperature superconducting single crystals and thin films for potential applications, and (3) the exploration of novel materials and structures with enhanced superconducting transition temperatures.
Experimental studies are performed using a variety of techniques including SQUID magnetometry, vibrating sample magnetometry, ac susceptometry, heat capacity, resistance, and current-vs-voltage characteristics from dc to microwave frequencies in the temperature range between 0.3 K and 400 K. Materials are synthesized in ceramic, single crystal and thin film forms with structural characterization by DTA/TG, X-ray diffraction, scanning electron microscopy with EDS, and atomic force microscopy.
The standard model of the strong interaction provides that the constituent quarks and gluons of hadrons (strongly interaction particles) are confined over a distance scale of approximately 1 x 10-15 meters, the characteristic size of the elementary particles. This confinement is thought to be absolute in the sense that individual quarks and gluons are not observable in free space. In the language of Quantum Chromodynamics (QCD), the theory of the strong interaction, quarks and gluons, which carry bare color charges, must combine in clusters to form color singlet states, the only states actually observable in nature. Thus, these color singlet states correspond to the spectrum of observed elementary physics.
Direct experimental study of the confinement of color is the domain of experimental Relativistic Heavy Ion Physics. While QCD specifies that observable physical states be color singlets, it does not specify the total volume over which such color singlets are established. Large nuclei, under normal conditions, consist of clusters of individual hadrons, in particular neutrons and protons in which the color remains confined inside the individual hadrons. This is apparently the ground state of QCD. Nuclear matter at sufficiently high temperature or density, however, may undergo a phase transition in which color is deconfined from the individual neutrons and protons only to be confined at a much larger volume corresponding to the volume of the entire nucleus. The resulting excited state of matter corresponds to the hypothetical state known as the quark/gluon plasma. In this state, quarks and gluons are free to move as though they were independent particles. The requirements of color confinement are still maintained outside the volume as a whole. The early universe, a few microseconds after the big bang, was probably a similar large volume of essentially free quarks and gluons. As time progressed and the universe expanded and cooled, the quark gluon plasma condensed to form the hadrons out of which all matter in the universe is made today.
Relativistic Heavy Ion Physics is the study of nucleus-nucleus collisions at high energies in order to understand the behavior of extended nuclear matter
under the extreme conditions of high density and temperature. The primary goal is to reach the phase transition from ordinary nuclear matter to a
quark-gluon plasma
The Wayne State University DOE supported experimental heavy ion group consists of four Faculty, four Research Associates, and four graduate students. Members of the group have been active collaborators in fixed target experiments E814, E877, E864, E896, E941 at the BNL AGS, as well as experiments NA45 and NA49 at the CERN SPS. A total of 47-refereed publications were produced by the above experiments. Of these, 30 were lead by members of our group. Nine Wayne State students received a degree based on their participation to these experiments. In recent years, members of the group have focused their activities on the development, deployment, and operation of the STAR experiment at the Relativistic Heavy Ion Collider, and on the analysis of the large body of data it produces. Members of the group have played critical roles in the development and deployment of the STAR experiment. We have had project management responsibility for the Silicon Vertex Tracker, SVT (Professor Bellwied), the Electromagnetic Calorimeter, EMC (Professor Cormier), the Online, and the integrated tracker (ITTF) projects (Professor Pruneau). STAR, after only three years of operations, has already published 31 refereed papers. Of these, 12 involved members of this group as primary authors, thereby making this group a strong leader of RHIC physics as well as its associated technologies. The group physics interests and analysis activities cut across many areas relative to the discovery and characterization of the quark gluon plasma (QGP). In essence, the group contributes to virtually all aspects the RHIC heavy ion program. Specific topics include the discovery (Professor Voloshin, first STAR paper) and study of flow at RHIC; the study of event-by-event fluctuations of transverse momentum, net charge, and chemical abundances; measurements of two-particle short (HBT) and long range correlations; measurements of strangeness production, equilibration, and flow; study of high pt particle production, and azimuthal correlations; and finally hard-probe studies with the EMC.
One of the great mysteries in physics is why the fundamental particles come in three and only three families. Studying the properties of the three families in detail is one way to further understand this mystery which is central to understanding the universe at a fundamental level.
The Wayne State BTeV/CLEO group is focused on investigating the properties of the quarks of the second and third families. CLEO is an experiment at Cornell that currently produces very large samples of the second family charm quark pairs in electron-positron collisions. This is a pristine environment and CLEO is a very capable detector able to see both charged and neutral particles. These allow unmatched sensitivity to rare behavior and unparalleled accuracy in measurements of the charm quark. We are focused on studying charm decays to three bodies and the search for charm quarks spontaneously turning into anti-charm quarks.
BTeV is an experiment under construction at Fermilab. It focuses on measurements of the bottom and charm quarks produced in the collisions of protons and anti-protons. BTeV uses a very accurate pixel silicon detector to accurately measure charged tracks attached to a super computer that in real time distinguish bottom and charm quarks from the background. We work on the pixel detector focusing on the problem of keeping the detector, which produces 3 kilowatts of heat, cool within the high vacuum of the Fermilab ring.
We also work on the physics of particle accelerators. When the intense beams of particles collide the electric field of one beam causes the particles of the other beam to radiate. This radiation can be measured to learn if the beams are colliding head on or not. Properties of the radiation also indicate exactly how the beams are missing each other and allow them to quickly be brought back into proper alignment. A prototype is in the electron-positron ring at Cornell and we are developing the detector for use in a future high-energy electron-positron linear collider.
Our research is supported by the National Science Foundation of the United States.
For more information on CLEO see http://w4.lns.cornell.edu/public/CLEO/
For more information on BTeV see http://www-btev.fnal.gov
The energy of the universe consists mainly of dark matter and dark energy. Little is known about the nature of either, but one or both may turn out to be sub-atomic particles. These particles may be produced in high energy particle collisions or they may affect the decay properties of established particles. Both methods are being pursued using the Collider Detector at Fermilab (CDF), located near Chicago. We study collisions of 980 GeV protons with anti-protons (p-bars) of the same energy, but opposite direction. The Fermilab Tevatron accelerator, which produces these collisions, is the highest energy particle accelerator in the world.
The CDF can identify new, large mass particles produced in the pbar-p collisions. For example, the elusive Higgs boson is predicted to have a mass of about 120 times the mass of the proton. Another class of large mass particles which has been hypothesized are the supersymmetric particles, some of which may be types of dark matter.
Particles containing the charm quark are produced copiously in the pbar-p collisions at Fermilab. The Wayne State group is studying rare decays of charm particles for evidence that the decays are affected by the existence of previously undiscovered, high mass particles.
The Wayne State group maintains operation of the front-end electronics for the CDF calorimeters. The calorimeters are a key part of the CDF apparatus and are used to measure the energy of pions (and other strongly interacting particles) as well as electrons.
A new accelerator is under development by the world-wide physics community: a high energy electron-positron linear collider. This accelerator could make precise measurements of the properties of new, high mass particles. The detector for the collisions produced by the linear collider will require novel technologies. At Wayne State, we are developing a prototype muon detector which could meet the requirements for accurate time resolution, good spatial granularity and stable long term operation.
Our research is supported by the United States Department of Energy.
For information about the CDF experiment see http://www-cdf.fnal.gov/pubcdf.html
For information about the Linear Collider see http://blueox.uoregon.edu/~lc/alcpg/
Recent Publications: D. Acosta et al. (CDF Collaboration), ``Search for the Flavor-Changing Neutral Current Decay D0 -> mu+ mu- in p-pbar Collisions at sqrt(s) = 1.96 TeV'', Phys. Rev. D68, 091101 (2003).
D. Acosta et al., (CDF Collaboration), ``Observation of the Narrow State X(3872) -> J/psi pi+ pi- in p-pbar Collisions at sqrt(s) = 1.96 TeV", to appear in Phys. Rev. Lett. (2004).
The emphasis of our work is on studying the scattering of positrons (antiparticles of electrons) and electrons from various atoms and molecules. The systems under current investigation include rare gas atoms, alkali atoms and light molecules. We have also calculated and compared the cross sections for the ionization of inner shells of various atoms by impact of both positrons and electrons.
Other research interests include investigations of production of negative ions by the process of dissociative electron attachment to simple molecules. The rates of negative ion production by this process are strongly enhanced if the attaching molecule is initially rovibrationally excited. We have also calculated the cross sections for the vibrational excitation and dissociation of simple molecules by electron impact. Atomic and molecular collision processes play important and significant roles in astronomy and astrophysics.
The nature of the atomic-scale defects in semiconductors often determines the optical, electronic, and structural properties of these materials, and how these properties change with time, heating, pressure, and application of fields. Our research group investigates the properties of the important defects and defect complexes occurring in various semiconductors. In order to be able to identify the defects responsible for particular experimental properties (and suggest how to optimize these properties as desired for particular applications), we use first-principles quantum molecular dynamics calculations to search for low energy defect structures, characterize the electronic and optical properties of these low-energy defects, and compare these properties with the experimental observations. We also determine whether these energetically favorable defects have metastable higher energy configurations, and investigate their motion and interactions. Since these calculations are very demanding, they are supported by grants of supercomputing time from the Air Force Office of Scientific Research at ERDC, NAVO, and other national supercomputing centers.
There is currently a lot of interest in producing nanoscale devices and low-dimensional structures, such as quantum dots, in order to achieve faster response times, and the possibility of modifying the properties as desired by changing the geometrical dimensions. While changing the conditions during growth and processing can affect the quality of surfaces and interfaces and the concentrations of various defects remaining in important regions in larger devices as well, this can produce particularly dramatic changes in the properties of low-dimensional or very small structures. Therefore a better understanding of semiconductor growth at the atomic level is needed. Our research group is currently investigating how growth and processing under different conditions can lead to different concentrations of structural defects at the surface, and different concentrations of various defects remaining in the material after growth. In order to address these questions, we use first-principles calculations to study the dynamics and energetics of the microscopic processes occurring at the growing semiconductor surfaces, as well as the defects which can occur at the growing surface.
References and an overview of some of the first-principles methods we use, including codes written and maintained by our long-term collaborators at the Fritz-Haber-Institut der Max-Planck-Gesellschaft and a manual on how to do these calculations coauthored by us, is available at http://www.fhi-berlin.mpg.de/th/fhi98md.
Some recent publications:
First-Principles Study of As Interstitials in GaAs: Convergence, Relaxation, and Formation Energy, J. T. Schick, C. G. Morgan, and P. Papoulias, Physical Review B 66 195302 (2002).
Optical and Electrical Properties of Low to Highly Degenerate InN Films, D. B. Haddad et al., Mat Res. Soc. Symp. Proc. 798 Y12.7.1-Y12.7.6 (2004)..
Theoretical studies concentrate on understanding the microwave responses of layered superconductors and the physics of the dynamic states arising from the Josephson tunneling in these layered superconductors.
Theoretical high-energy nuclear research lead by Sean Gavin brings cutting edge theoretical techniques to bear on the dynamics of the quark-gluon plasma and relativistic heavy ion collisions. Gavins research has touched almost every problem in this active field. Best known for his work on charmonium production, he has done highly cited and important work on several very different problems in this field, including thermalization, disoriented chiral condensates, parton energy loss, HBT and correlations. Methods he has used include quantum field theory, QCD perturbation theory, and nonequilibrium statistical mechanics. Computational methods range from pencil-and paper to numerical simulations on our 20 CPU Linux array. In the last three years he guided and supported the research of five graduate students, leading to one completed PhD as of 2004. These efforts are supported in part by a U.S. National Science foundation CAREER award.
Experiments at the Relativistic Heavy Ion Collider in the U.S. and at the Large Hadron Collider in Switzerland during the later part of the decade permit studies of the collisions of large nuclei at the highest available energies. The theoretical challenge is to reconstruct the state of the highly excited quark-gluon plasma formed in these collisions from the plethora of particles seen in the laboratory. To confront this challenge, we are working to understand the statistical mechanics of this quark gluon plasma together with the dynamics of how it is produced. We employ methods from such diverse areas as relativistic quantum field theory, QCD, nonequilibrium statistical mechanics and the dynamics of phase transitions.
A major goal of the experimental effort to study the physics of B mesons is to explore the features of the phenomenon of CP violation, to test the Standard Model of particle physics, and to search for the glimpses of New Physics at higher energies. The theoretical research effort of the group overlaps significantly with these goals. Current interests of the group include QCD phenomenology, mainly in applications to the heavy quark systems, and studies of CP violation. Current projects include investigations of meson mixing phenomena in B as well as in D systems, decays and production of conventional and hybrid quarkonia, and understanding the nature of non-perturbative effects in various decays of K mesons.
Studies of interacting systems and their stability. Specifically, the application of the mathematical concepts of recursive relations, chaos, and complexity, to the system of armed competing states. The goal is to attain insight into how to make international security policy-what choices will lead to dangerous international instability and the probability of war.