These are sample projects from Summer 2017. They will be updated before the Summer 2018 offers are made.

New Classes of Fluid Instabilities in 3D Printing of Soft Matter Prof. Thomas Angelini
Electric field effect on the magnetism of La0.33Pr0.34Ca0.33MnO3 Prof. Amlan Biswas
Optically Pumped NMR in III-V Nanostructures Prof. Russ Bowers
High-pressure studies of unconventional superconductors Prof. James Hamlin
Computational Discovery and Design of 2D Materials for Electronic and Energy Applications Prof. Richard Hennig
Modeling Thermoelectric Transport at the Nanoscale Prof. Selman Hershfield
Micro-electro-mechanical oscillators Prof. Yoonseok Lee
Universality of Vortex Formation Prof. Kamran Mohseni
Analog Simulation of Interacting Quadrupolar Molecular Systems Prof. Neil Sullivan
Quantum phase transitions in low-dimensional antiferromagnets Prof. Yasu Takano
Acoustic Spectroscopy of Ferroelectric This Films and Their Crystal Phase Transition Prof. Roozbeh Tabrizian
Preparing to measure vacuum birefringence Prof. David Tanner &
Prof. Guido Mueller


New Classes of Fluid Instabilities in 3D Printing of Soft Matter, Prof. Thomas Angelini
        Technology for 3D printing with hard materials is in a very mature state; hobbyists can 3D print hard thermoplastics with high precision at low costs. Many important applications in medicine require the use of soft materials, like hydrogels and elastomers, which have the feel of Jell-O or soft rubber. The recent invention of a soft matter 3D printing technique at the University of Florida has opened the door to 3D printing precise objects made from soft matter. However, the new combinations of complex soft materials involved in this 3D printing technique have generated unanticipated fluid instabilities. The physical principles that control these instabilities have not yet been determined, limiting our ability to advance the technology.
        The REU student will 3D print simple platonic shapes like lines, spheres, cylinders, and planes and study their evolution under destabilizing forces. The shapes will be made from a viscous or viscoelastic liquid and suspended in 3D space without any support apart from an embedding continuum. The embedding material is a granular-gel based liquid-like solid which, as its name implies, is a solid from a technical thermodynamic perspective yet also possesses many of the properties of a liquid. The student will perform time-lapse microscopy and photography and learn digital image processing techniques for data analysis.

Electric field effect on the magnetism of La0.33Pr0.34Ca0.33MnO3, Prof. Amlan Biswas
        Ferromagnetic materials such as iron can be permanently magnetized using a magnetic field and are therefore used for data storage. In certain materials it is also possible to control the magnetism using an electric field which is of great interest both due to the underlying physics and possible device applications. In this project we will study a compound with chemical formula La0.33Pr0.34Ca0.33MnO3 (LPCMO), which is a ferromagnet and non-magnetic phases coexist forming a multiphase state in which ferromagnetic islands are formed in a non-magnetic matrix. While the material is a crystalline solid, the ferromagnetic phase can move like a fluid in the non-magnetic matrix. The main goal of this project is to use an electric field to reshape the fluid-like ferromagnetic phase and thus control the magnetic properties using an electric field.
        The REU student will characterize the properties of the thin film samples using scanning probe microscopy, transport, and magnetization measurements. Once the basic properties have been optimized, the student will study the effect of an electric field on the resistance and magnetization of LPCMO. The main techniques that the student will learn are scanning probe microscopy, low temperature resistance and magnetization measurements, and photolithography for fabricating micro/nanostructures of LPCMO.

Optically Pumped Nuclear Magnetic Resonance in Quantum-Confined GaAs Nanostructures, Prof. Russ Bowers
        Nuclear Magnetic Resonance (NMR) is a powerful form of radio frequency spectroscopy involving nuclear spin transitions in an applied magnetic field. In III-V semiconductors such as GaAs, nuclear spin polarization can be induced by pumping of optical interband transitions, resulting in milli-Kelvin nuclear spin temperatures. The NMR signal enhancement, which can exceed 4 orders of magnitude, facilitates NMR experiments on nuclei located in the small quantum confined volume in III-V semiconductor layers (e.g. GaAs) as thin as 4 nm. The optical pumping effect depends on many variables, including the electronic band structure, magnetic field, temperature, optical polarization, strain, electron-nuclear spin dynamics and nuclear spin diffusion. Potential applications include spin quantum computing.
        The REU student will attempt to observe OPNMR effects in types of inorganic semiconductors where it has never been observed before. Examples include wide-gap (e.g. GaN), mid-gap (GaP) and narrow-gap (InAsP) materials. The dilute magnetic semiconductor GaMnAs is also of interest. OPNMR experiments will be performed on thin film samples exposed to in-situ laser irradiation at high magnetic fields and low temperatures (down to ~1.5 K). Quantum confinement and strain effects which modify the electronic band structure may also be studied. The student involved in this project will gain experience in low-temperature NMR techniques, near infrared optical spectroscopy and laser systems,and semiconductor physics.

High-pressure studies of unconventional superconductors, Prof. James Hamlin
        Superconductivity is a phenomena with enormous applications potential. However, this promise has yet to be fully realized, in part because of our incomplete understanding of the conditions under which superconductivity develops in certain materials. The Hamlin group is utilizing applied high pressures both to understand the properties of known superconductors and to help discover new ones. Pressure is a powerful control parameter, capable of rapidly and continuously tuning a single sample between insulating, metallic, magnetic, or superconducting ground states.
        The REU student will participate in the synthesis of new materials, particularly in single crystalline form, and will learn about the characterization of these materials by x-ray diffraction, electrical transport, magnetic susceptibility, and specific heat measurements. The student will also gain experience in the use of diamond anvil cells, which allow the application of pressures spanning the range from kilobars (the pressure at the bottom of the ocean) to megabars (nearing the pressure at the center of the earth).

Computational Discovery and Design of 2D Materials for Electronic and Energy Applications, Prof. Richard Hennig
        The rapid rise of novel two dimensional (2D) materials, presents the exciting opportunity for materials science to explore an entirely new class of materials. This comes at the time when mature computational methods provide the predictive capability to enable the computational discovery, characterization, and design of 2D materials and provide the needed input and guidance to experimental studies. Materials informatics approaches such as data-mining and genetic algorithm can identify novel 2D materials with unexpected structures and unusual properties.
        In this project the REU student will learn how to use materials informatics tools and perform high-throughput simulations to discover new 2D materials. We will use density-functional theory to characterize these materials and determine their electronic and magnetic properties, and identify possible applications for these materials as photovoltaics, photocatalysis, transistors, spintronics, etc. The student will gain experience in solid-state physics, computer simulations, and materials informatics.

Modeling Thermoelectric Transport at the Nanoscale, Prof. Selman Hershfield
        There is renewed interest in using thermoelectricity to harvest waste heat. For example, as much as 70% of the energy from car engines is lost to heat. Bulk thermoelectric generators are not efficient enough to be cost effective except in very specialized applications such as space exploration. However, at the nanoscale one can design systems which have in principle a higher efficiency and can be scaled up by placing many devices in parallel.
        In this project the REU student will use existing computer code written in Matlab to compute the transmission of electrons and phonons (lattice vibrations) through a quantum wire such as a nanotube or semiconducting wire. Some programing will be necessary to create the energy matrix (hamiltonian) for the system. From the transmission probabilities the student will compute the electron and phonon thermal conductivities as well as the thermoelectric voltage generated. The student will gain experience running computer simulations and learn solid state physics related to thermoelectricity.

Micro-electro-mechanical oscillators, Prof. Yoonseok Lee
        Micro-electro-mechanical systems (MEMS) are used extensively in both industry and science as accelerometers, pressure sensors, strain gauges, etc. The Lee group has developed MEMS oscillators as a unique experimental probe to study the properties of liquid He at ultra low temperature environment. The devices have been tested and employed in the study of superfluid helium three down to 0.25 mK. Now a new generation of devices are under production. The REU student will participate in characterizing the new generation MEMS devices, which include 6 by 6 arrays reminiscent of a pixel CCD, and perform a computer simulation in close collaboration with a graduate student in Prof. Lee's group. The student will acquire knowledge and experience of MEMS devices, a mechanical resonator -- one of the most important theoretical and practical subjects in physics -- as well as experimental techniques involved in detection and actuation.
        The REU student will participate in characterizing the new generation MEMS devices, which include 6 by 6 arrays reminiscent of a pixel CCD, and perform a computer simulation in close collaboration with a graduate student in Prof. Lee's group. The student will acquire knowledge and experience of MEMS devices, a mechanical resonator -- one of the most important theoretical and practical subjects in physics -- as well as experimental techniques involved in detection and actuation.

Universality of Vortex Formation, Prof. Kamran Mohensi
        Vortices are the building blocks of many complex flows. Of particular interest to our group is the role of vortices in bio-propulsion. Squid and jellyfish use creation of vortex rings for propulsion and feeding. Similarly leading edge vortices play a significant role in generating lift in flapping flyers.
        The REU student will use experimental techniques such as particle image velocimetry and high speed videography to to investigate the properties of these vortices related to force generation. They will learn about fluid dynamics and vortex formation, as well as the use of high speed imaging techniques to study complex fluid flow.

Quantum phase transitions in low-dimensional antiferromagnets, Prof. Yasu Takano
        In some antiferromagnets, the dipole moments form a one- or two-dimensional array rather than a three-dimensional periodic structure. The quantum (or zero-absolute-temperature) phase transitions of such low-dimensional antiferromagnets are poorly understood and are presently the subjects of many experimental and theoretical studies.
        The REU student will measure the heat capacity of novel low-dimensional antiferromagnets at temperatures below 10 K to gain microscopic insights into the macroscopic properties near zero temperature. The student will become familiar with experimental techniques at low temperatures and use of computers in data acquisition and analysis, as well as various elements of modern magnetism and thermal physics. The student will participate in a five-day experiment at the National High Magnetic Field Laboratory in Tallahassee if magnet time is available.

Analog Simulation of Interacting Quadrupolar Molecular Systems, Prof. Neil Sullivan
        Diatomic molecules such as H2 and N2 do not have an electric dipole moment, but they do have an electric quadrupole moment. The short range interaction between these moments is important for understanding the ordering in solid H2, N2, and other molecular systems. Systems of interacting quadrupoles are frequently frustrated, meaning that it is not possible to have all nearest neighbor pairs in their lowest energy state. They can also be disordered. Understanding the collective excitations of interacting, frustrated, and disordered systems is one of the central themes in condensed matter physics.
        In this project the REU student will simulate the collective excitations of diatomic molecules using a two dimensional array of magnetic quadrupoles that are free to rotate about one axis. The student will design probes both for creating and measuring excitations and will interface these probes to a computer. The REU student will learn about analog electronics, computer data acquisition, and the physics of complex interacting quadrupoles.

Acoustic Spectroscopy of Ferroelectric Thin Films and Their Crystal Phase Transition, Prof. Roozbeh Tabrizian
        Ferroelectric materials have a permanent electric dipole moment just as ferromagnets have a permanent magnetic dipole moment. Ferroelectric materials have numerous applications such as in RFID cards and in ferroelectric RAM for computers. This project targets design and implementation of micro- and nano-mechanical resonators to serve as test-vehicles for in-situ spectroscopy of ultra-thin ferroelectric films. Acoustically engineered waveguides and phonon traps will be used to extract several material properties of Atomic Layer Deposited ferroelectric films with sub-20nm thicknesses. Specifically, these devices will serve for real-time monitoring of crystal phase transitions in ferroelectric thin films upon in-situ ovenization or ex-situ thermal treatments.
        The project includes design and implementation of acoustic test-vehicles with integrated piezoelectric transducers, electrical and optical characterization of test-vehicles, and experimental data acquisition and analysis. The REU student will contribute to each step of the cycle. They will learn about electrical, optical, and acoustical measurements and gain hands-on experience with experimental data acquisition and analysis.

Preparing to measure vacuum birefringence, Prof. David Tanner and Prof. Guido Mueller
        Vacuum birefringence was predicted by Heisenberg and Euler 80 years ago and finally today we have the technology in hand to measure it. However, such a sensitive experiment requires detailed preparation and studies to understand all sources of noise and, even more important, systematic effects which could mask the main signal. One of these effects is birefringence from optical components which are nominally non-birefringent such as mirrors under normal incidence. We have set up an experiment to measure the birefringence of mirrors under normal incidence. The REU student will study the dependence of the birefringence on parameters like the number of coating layers of the mirror under study, the beam size, external magnetic fields, and small deviations in angles.
        The REU student will work closely with a graduate student. The work will include alignment of optics, reliable offset phase locking of lasers, and finally measuring the birefringence by measuring the phase shift in beat notes between two laser fields. The REU student will thus gain experience working with high performance, single frequency lasers and performing high precision optical measurements. The entire project is embedded in our work towards a single photon detector, a dark matter detector and laser interferometric gravitational wave observatories.