A brief description of each research area along with selected papers and related links are supplied to provide the Fellows with relevant background material.
Baylor Department of Physics Summaries
Theoretical Surface Physics – Greg Benesh
Dr. Benesh and colleagues will be engaged in the computational study of the electronic structure of various metallic surfaces. They have developed a self-consistent method in which the exact influence of an infinite bulk substrate is communicated through an embedding potential. This method effectively treats the surface as a semi-infinite crystal instead of as a slab or slab-superlattice. Such a treatment is important for experiments such as angle-resolved photoemission and inverse photoemission spectroscopies, which probe the spectrum of electronic states; these states can be very different in a slab from those of a semi-infinite system. On surfaces of aluminum, nickel, and platinum the method has been shown to yield better work functions and more exact surface state energies than slabs of much greater thickness.
One project focuses on the shift of core-level energies at the surfaces of transition metals such as rhodium and tantalum. These shifts are important for understanding the interplay of environmental, relaxation, and charge transfer effects at surfaces. In 2005, an REU student calculated the effect of a screened core hole on the kinetic energy of an outgoing core electron.
We are also interested in studying surface magnetism in transition metals and in transition metal overlayers grown epitaxially on non-magnetic crystals. Enhanced magnetism at the surface has been observed in many of these materials. Ferromagnetic ordering has also been observed on the (001) surface of (paramagnetic) vanadium; however, theoretical calculations thus far are in disagreement -- predicting zero magnetic moment for surface vanadium atoms.
Journal of Physics: Condensed Matter 9, 8359-8368 (1997)
Physical Review B 54, 5940-5945 (1996)
Physical Review B 49, 17264-17272 (1994)
Chemical Physics Letters, 191, 315-319 (1992)
Experimental High Energy Physics - Jay R. Dittmann
The Experimental High Energy Physics group at Baylor is engaged in elementary particle physics research at the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois. At Fermilab, protons and antiprotons are accelerated to nearly the speed of light by the Tevatron, the most powerful particle accelerator in the world. Beams of protons and antiprotons collide at the center of two 5,000-ton detectors, and data recorded from these energetic collisions help physicists to identify the properties of the elementary particles that make up the universe. REU students who join Baylor's High Energy Physics group during the summer will have an opportunity to learn the fundamentals of high energy physics research. You'll learn the answer to questions like: How does a particle accelerator work? What happens when matter and antimatter collide? How do physicists detect particles that emerge from proton-antiproton collisions? At Baylor, you'll have the opportunity to analyze actual data from particle collisions or to create software that is useful for the operation of one of the huge particle detectors. This project is especially well suited to students who are skilled with computers and have some experience with C++ or java.
Experimental Non-equilibrium Dynamics - Jeffrey S. Olafsen
Dr. Olafsen's research interests focus primarily on macroscopic systems driven far from equilibrium. However, a dynamic balance between energy input and dissipation allows the systems to be observed in their steady-state. Developing a treatment for the statistical behavior of multi-particle systems driven far from equilibrium is the primary goal of the research. We approach this goal primarily through experiments (and some simulations) to study the dynamics. The tools typically employed are CCD imaging and image analysis of the global and local dynamics within these systems and to probe for universal behavior across experimental designs. Students will be responsible for a wide variety of investigations in tabletop experimental systems that incorporate mechanical and electrical details for controlling systems. CCD imaging and student-authored image analysis algorithms allow us to extract data for analysis. The investigations are computer intensive but allow the student to obtain the full breadth of experience from the mechanical and electrical design of the experiment to the data taking and analysis of the dynamics in the system.
Experimental Semiconductor Physics - Linda Olafsen
The semiconductor laser optics group is focused on the development of high efficiency, room temperature mid-infrared lasers for a variety of applications. In the long term, this work has potential to impact environmental monitoring and homeland security through the development of efficient, portable chemical sensors and infrared countermeasures. Conventional semiconductor lasers are electrically driven; electrons are injected as current, and those electrons make radiative transitions resulting in the emission of light. While ideally lasers will operate in direct current (dc) mode or at high duty cycles (long pulses and/or high frequency), it is often necessary to operate devices with very short pulses. The goal of this project is to model the pulsed current-voltage characteristics of diodes to better understand the pulsed operation of semiconductor lasers. The project will begin with modeling simple systems such as resistors and capacitors to see what "square" pulses look like as a function of time (including rise time and fall time). Other components will be added to this model to look at the effects of lead resistance and capacitance on measurements of diode characteristics. The ultimate goal is to understand the current-voltage characteristics of an LED or laser diode separate from the other electronic components (capacitance, lead resistance) in the circuit.
Experimental Surface Chemical Physics – Zhenrong Zhang
Dr. Zhang's research program aims at 1) the synthesis of controlled inverse model oxide nanocatalysts and 2) the atomic-level understanding of their structure-activity relationships. The hydrogenation of CO and CO2 is of great interest in the conversion of CO2 into liquid fuel. The basic research effort in nanostructured catalysis could provide new methods for design, synthesis, and characterization of catalysts with unique properties. The goal of this project is to investigate CO, CO2 and alcohol molecules adsorption and dissociation on inverse model catalyst surfaces of TiOx nanostructures and ultrathin films supported on single crystal Au surfaces. The films will be prepared using a molecular beam epitaxial method in an ultra-high vacuum (UHV) chamber. Scanning tunneling microscopy (SPM) coupled with other UHV electron spectroscopic methods will be employed to achieve a detailed understanding of the growth of controllable oxide nanostructures and ultrathin films. The controlled synthesis of oxide nanocatalysts will enrich the preparation of novel nanocatalysts. More importantly, the influence of the surface structure and the oxide/metal interface on the promotion action of transition metal oxides on the reactivity of metal surfaces will be investigated.