Condensed matter physics includes the study of solids (solid state physics) as well as liquids. Nationally, condensed matter physics is the largest and most active area of physics research, comprising a wide range of topics. For example, the annual March meeting of the American Physical Society is the largest meeting of its kind with more than 5000 presentations reporting research activities primarily in condensed matter physics. The growth and size of this meeting each year reflects the growth of this area of physics. Condensed matter physics is a vitally important and growing field of physics. Students with advanced degrees in this area can find employment.
Magnetic force microscopy (MFM) gives the possibility to image magnetic domains, through the dipolar interaction between the microscope probe and the magnetic stray field arising from the surface of the sample. We are currently using MFM to investigate the striped magnetic domains in CoPt films, as well as to try imaging the magnetic state of magnetite nanoparticles.
Magnetometry techniques allow the investigation of the magnetization behavior of a material under an in-situ magnetic field. We are planning to implement a Hall-Effect Magnetometer, as well as a Vibrating Sample Magnetometer. These devices will measure the magnetization as a function of magnetic field up to one tesla. In particular this will allow the measurement of hysteresis loops.
X-ray spectroscopy techniques give access to very small spatial and temporal scale information, by using the x-ray light produced by synchrotron radiation sources. We are using more specifically x-ray magnetic dichroism as well as x-ray magnetic scattering to investigate both the electronic and magnetic properties of the material. Furthermore we use coherent x-ray light at specific wavelengths in order to investigate the local morphology of the materials.
Optical measurements of spin lifetimes in semiconductors (Colton). Spin states of electrons in semiconductors have been proposed for use in prospective "quantum computers". In order to be a viable candidate for this type of quantum computer, the material has to have good spin properties -- specifically, the spins must not change states uncontrollably due to interactions with their environment, or at least the time scales of such state changes must be relatively long. This research has focused on experimental measurements of spin lifetimes in the semiconductor GaAs (gallium arsenide), its alloys, and in semiconductor nanostructures based on GaAs & alloys. Experimental techniques combine optical spectroscopies such as photoluminescence and reflectivity with magnetic resonance of the electron and nuclear spins. Experiments are done at very low temperatures (1.5 K) and large magnetic fields (1+ tesla).
Local and intermediate-range order in functional solid-state materials (Campbell). Systems of interest include fast-ion conductors, ferroelectric relaxors, magnetoresistive manganites, and microporous catalysts. Nanoscale structural features influence the macroscopic properties of many fascinating crystalline materials. These structures can be either static or dynamic, and consist of atomic displacements that spatially cooperate within regions as small as a nearest-neighbor bond (local order) or as large as a few tens of nanometers (intermediate-range order). Because atomic displacements are intimately coupled to other properties of interest, such as electronic and magnetic structure, vacancy or interstitial mobility, chemical reactivity, etc., structural defects or fluctuations modify local properties that, in many cases, also alter global properties.
We are developing new ways to "see" three-dimensional nanostructures in solid-state materials using advanced x-ray and neutron scattering tools, and to track them as a function of the properties that they influence. In addition to in-house diffraction experiments, we utilize state-of-the-art national and international scattering facilities, where we can probe subtle features that were previously inaccessible.
Nanoscale fabrication and imaging, experimental (Davis)
Biological Membrane Surface Imaging. The atomic force microscope is used to image soft biological structures in fluid with resolution down to the molecular level. Studies include membrane formation, protein incorporation and protein diffusion dynamics. In collaboration with David Busath (Physiology and Developmental Biology). Research supported by BYU mentoring funds.
Biomolecular electronics. Proteins and nucleic acids are candidate structures for self assembled molecular electronic materials. Conductivity measurements are performed on single horse spleen and bacterial ferritin molecules. In collaboration with Gary Watt (Chemistry and Biochemistry) and John Harb (Chemical Engineering). Research supported by NASA and BYU mentoring funds.
Nanoscale chemical patterning. Nanoscale chemical patterning of silicon and germanium surfaces has applications ranging from biomaterials to molecular electronics. An atomic force microscope probe is used to pattern surfaces with lines down to 20 nm across. In collaboration with Matthew Linford (Chemistry and Biochemistry). Research supported by NSF and BYU mentoring funds.
Nanotube mechanics. We are developing self-aligned processes for mechanical attachment of carbon nanotubes and perform atomic force microscope (AFM) based nanotube mechanics and adhesion and measurements. In collaboration with Matthew Linford (Chemistry and Biochemistry), David Tannenbaum (Pomona College), and Paul McEuen (Cornell University). Research supported by NSF.
Optical, transport and magnetic studies of nanostructured semiconductors (Hess). We study electron quantum mechanics in nanometer-scale semiconductors and molecular interconnects, by experiments with ultra-short pulse lasers, electron transport and magnetic resonance. This is part of a multidisciplinary collaboration of several faculty in physics and chemistry.
In our femtosecond laser laboratory, we use amplified ultra-short light pulses to track electron transitions between quantum states. Experiments include transient photo-induced absorption, up-conversion luminescence lifetime and other nonlinear optical spectroscopies with time resolution of less than 100 femtoseconds. Time-correlated-single-photon counting extends the dynamic range out to 50 microseconds. In addition, we use steady light sources for traditional spectroscopies and millisecond photomodulation studies.
Electron spin resonance allows us to detect unpaired spins, which are of particular importance at surfaces and interfaces, and in doped semiconductor nanocrystals.
We combine optical and transport studies to understand the localization of the electron states, alignment of levels in nanocrystals and interconnects, and the influence of excess charge in the nanocrystals.
This research has applications to new computing technologies, solar cells, nonlinear optical switches, and light emitting diodes for displays.
Phase transitions in solids, theoretical and computational (Stokes). When a solid changes its internal structure, interesting new physical properties may appear. Often these properties can be predicted and the material can be utilized for a particular purpose, for example, as superconductors, as ferroelectrics in copiers, as piezoelectrics in sensors, etc.
We apply principles of group theory to the study these transitions between different crystalline structures. This project has been ongoing since 1983. We have developed software that allows us to generalize our group-theoretical methods to a large number of possible cases that may be observed experimentally. Most recently, we have developed an web application, ISODISTORT, with a user-friendly graphical interface as well as visualization tools.