The primary focus of our group is the development, characterization, and study of new micro- and nanostructured materials (mostly transition metal oxides – but not to the complete exclusion of other materials).
Nanoscience and nanotechnology continue to be subjects of active research and continue to catch both the eye and the funding of key government agencies. Results from these areas impact not only the basic understanding of nanoscience, but also the foundations of a number of sub-branches of physics. Even more importantly, the potential outcomes and associated potential applications (e.g., detection of CBE warfare agents, non-destructive material evaluation, ultrafast computing and communication, etc., etc.) make these topics germane to a broad array of communities.
Although it has been studied since 1959, vanadium dioxide (VO2) research is undergoing resurgence. This resurgence is due (at least in part) to the inclusion of noble metal nanostructures with the VO2 – thus taking advantage of the local surface plasmon resonance (LSPR) effects. The LSPR of metal nanoparticles is highly sensitive to their size, shape, surrounding medium, and interactions with other nanoparticles, making them ideal nanoantennae, sensitive to changes in their local environment, and capable of serving as detectors contaminants. In addition, the precise tunability of the optical properties of these subwavelength structures has aided the creation of metamaterials, in which the macroscopic optical properties are dictated and manipulated by the underlying arrangement of nanostructures; this is analogous to the optical response of (subwavelength) single molecules and atoms determining the optical properties of the macroscopic medium. Due to this tunability at both the nanoscale and at macroscopic scales, simple metal nanoparticles and more complex nanostructures, such as split rings, are playing a critical role in emerging nanotechnologies with a vast range of applications. The false-color image to the right is a 10-nm thick film of vanadium dioxide (yellow) on a c-cut sapphire substrate (blue) created with an electron-beam evaporation system and imaged with an atomic force microscope – both of which are located in our laboratory. The "step" between the blue area and the yellow area is from the sample holder than "shields" part of the substrate from deposition.
Our group, as a part of both the Texas Tech University Department of Physics and the Nano Tech Center at Texas Tech, is working on a number of projects in collaboration with the Vanderbilt University Departments of Physics and Chemistry, the Vanderbilt Institute of Nanoscale Science and Engineering, and the United States Naval Research Laboratory.
Our initial main laboratory instrumentation is almost complete and is described on the laboratory webpage.
Virtually all of my research programs provide opportunities for students to become involved in research at all levels: even early undergraduate students can contribute by managing simulation runs, postprocessing results, taking and reducing data, and completing analysis; more advanced undergraduate students and early graduate students can contribute in innumerable ways, such as development of new simulation methods, development of realistic but computationally tractable models, and detailed analysis of simulation results against experimental data and theoretical predictions. Doctoral students in these areas should, of course, need to do a project that combines some elements of theoretical development, algorithm development, simulation, experimentation/observation, and analysis.
Any students wishing to take part in any of this research should feel free to come by Room 003 in the Science Building.
One of my colleagues describes a modeling philosophy with which I agree completely. It includes:
This last point is critical. In many cases, it is both very time consuming and expensive to test every point in a given multi-dimensional parameter space. Therefore, it is absolutely critical that we use modeling and approximations to help guide our experimental and observational efforts.
Because of my highly non-traditional career, my research interests span a wide variety of topics. In general, I still maintain active research projects in the following areas:
Observing and modeling A and F stars with an emphasis on asteroseismology
Stars are the most fundamental elements in the universe. Galaxies are made of huge numbers of stars; cosmology depends greatly upon them, and so it is vital that we understand them – otherwise, everything else that we do is effectively playing around and just hoping we might be right. Asteroseismology is the key to understanding stars. It will ensure that we understand stellar structure and evolution, which means that it will enable us to verify the most basic physics within astronomy. Things like opacities, nuclear reaction cross sections, nuclear reaction rates, and energy transport will all be put to the test. Now that the CoRoT and Kepler satellites have returned an enormous amount of data, true asteroseismology (similar to helioseismology) can actually begin.
A and F-type dwarfs are vital in our understanding of stars. They lie at the crossroads between hot O and B stars and the cooler G, K, and M stars. They lie at the boundary where convection becomes important, where alpha-omega magnetic fields come into play, where solar-type oscillations may be observed, and where "classical" kappa-mechanism-driven pulsations begin and end. Others might call them the "bloody" F stars, but they're beautiful, and absolutely key to understanding not only stellar astrophysics, but all the other applications that depend upon phenomena that occur under similar conditions.
My research group focuses largely on the analysis of photometric and spectroscopic data for these stars. We use data from satellite observations and from ground-based observing campaigns to better understand the cause(s) of variability in these stars. Once the variations are well characterized, we try to place them into a context where we can better understand each particular star and how it fits into the overall picture. We are closely tied to theoretical models and to theorists, and we constantly strive to improve our methodology so that our results allow the physics to tell us what is happening (rather than trying to force a particular model onto the data).
Just because we focus on A and F stars does not mean that we ignore all of the other interesting astrophysics that's going on. We also work on the Be star phenomenon, and study the interaction of rotation and convection across the Hertzsprung-Russell diagram.
When I arrived at Texas Tech, I sought out other people with similar interests. Given the current world events at the time, I began a project in collaboration with TTU's Department of Geosciences to characterize man-made seismic signals. There's no doubt that nature (and the DPRK) supplied us with some wonderful data for a number of projects.
Just as we can use asteroseismic data to determine the inner structure of a star (see above), using earthquake data, we can determine the inner structure of the Earth. We can also determine from where the source emanated and how much energy was released in a given event. This collection of projects is similar to the asteroseismology projects in that they are both classes of inversion problems (i.e., we have some information, and we are trying to glean something about what generated the information or something about the medium through which the information passed without knowing too much a priori). These are highly complementary programs, are we hope to link the two departments more closely and take advantage of tools each has developed to assist the other.
Understanding the time evolution of a signal or a series of signals and being able to interpret the results has always been a problem of critical importance (just ask your financial advisor). Luckily, this is one of the overarching tools for many of the ongoing projects in my research group that is being used to understand and predict a wide range of phenomena.
We take full advantge of the data, both in the time domain and in the frequency domain, and we are developing new tools to squeeze more information out of the data than ever before.
This graphic showing the detection of two distinct gravity-mode puslations in the gamma Doradus star HD 68192 at frequencies of roughly 0.769 and 0.832 cycles per day (corresponding to periods of 1.300 and 1.202 days, respectively) was originally published by Kaye et al. in The Astronomical Journal in December 1999 (Vol. 118, pp. 2997-3005).
In addition to the projects listed above, we have ongoing, active research in the following areas: