Electric field effect on the magnetism of La0.33Pr0.34Ca0.33MnO3 Prof. Amlan Biswas
High-pressure studies of unconventional superconductors Prof. James Hamlin
Computational Exploration of Geometries for Organic Solar Cells Prof. Selman Hershfield
Simulations and measurements of coupled low-dimensional systems in the quantum regime Prof. Dominique Laroche
Magnetism in Materials of Many Flavors Prof. Mark Meisel
Entropy-stabilzed Cuprate Superconductors Prof. Ryan Need
Plasmonic Nanomaterials for Energy, Environment, and Biomedicine Prof. Wei David Wei
Modeling Spin-Lattice Coupling in Molecular Magnets Prof. Xiaoguang Zhang
Optical Properties of Two Dimensional Materials Prof. Xiao-Xiao Zhang


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 measure the effect of this reshaping using planar Hall effect measurements.
        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 then measure the planar Hall effect in LPCMO microstructures using a new home-built cryostat. This technique is expected to reveal changes in the magnetic properties of LPCMO due to applied electric fields. The student will be trained to use apparatus such as, scanning probe microscopes and superconducting magnets.

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).
        If we cannot accommodate the student in the laboratory due to the pandemic, the student will engage in a complementary part of the project that is focused on data mining and machine learning methods to identify materials that exhibit novel high temperature superconducting states at high pressure.

Computational Exploration of Geometries for Organic Solar Cells, Prof. Selman Hershfield
        Solar cells composed of organic semiconductors have the potential to greatly reduce the cost of solar cells. However, these solar cells are less effiecient than traditional solar cells because the active region for converting light to electric current is much smaller than with conventional semiconductors like silicon. This inefficiency is partially overcome by mixing the p-type and n-type organic semiconductors to create more surface area in what is called a bulk heterojunction. The question addressed in this project is by how much can one increase the efficiency by mixing the p-type and n-type materials in an organized rather than random fashion. For example, one could consider pillars of a p-type material embedded in an n-type material. Much more complex geometries are possible to explore computationally.
        The REU student will use existing three dimensional simulation software after first writing a simplified one dimensional version themselves to understand the physics involved. This software was used by a previous REU student student to study the effect of varying the percentage of p-type and n-type material in a random sample (REU paper, CUWiP poster). The REU student will learn about the physics of organic solar cells and how to run simulations. After an initial learnign period, the student background will run jobs on the University of Florida's HiPerGator supercomputer to use machine learning techniques to optimize geometry and maximize power for a given set of materials parameters.

Simulations and measurements of coupled low-dimensional systems in the quantum regime, Prof. Dominique Laroche
        At low-temperatures, electrons whose motion is confined to 1 or 2 dimensions clearly exhibit their quantum natures. The coupling of such low-dimensional systems at the nanoscale enables the study of novel and exotic quantum states, such as the one-dimensional Luttinger liquid regime, where the excitations of fermions (electrons) actually behave like bosons. Other examples include the creation of Majorana quasiparticles, which is the condensed matter analog of a particle which is its own antiparticle, and the formation of exciton, which enables the study of superfluidity, the charge-neutral analog of superconductivity. To observe these phenomena, Prof. Dominique Laroche uses nanoscale fabrication and low temperature physics measurement techniques.
        In this project the REU student will take part in the simulation, the packaging and the testing at cryogenic temperatures of coupled nano-devices. Projects related to the study of exciton condensation in coupled 2D systems and to the study of interactions within the Luttinger liquid model in coupled 1D systems will be available. The REU student will learn methods to simulate the properties of these systems as well as hands-on experimental techniques for contacting and manipulating nano-devices, and for performing low temperature electronic measurements. They will also learn about the exciting field of quantum matter in low-dimensional systems.

Magnetism in Materials of Many Flavors, Prof. Mark Meisel
        The group of Prof. Meisel studies magnetism in a wide variety of materials including molecular-based, high entropy alloys, systems studied in high magnetic fields, and steels processed in and out of magnetic fields. The magnetic behavior of these systems is measured in a range from very low temperatures to high temperatures and from zero magnetic field to very high magnetic fields. Depending on the system studied, different measurement techniques are used to find the "magnetic fingerprints" of the materials.
        The REU student will measure the magnetic properties of some of these new materials using either a Superconducting Quantum Interference Device (SQUID) magnetometer or a new instrument being developed for high temperature studies. The student may have an opportunity to use Labview, Solidworks, lock-in amplifiers, temperature controllers, and other experimental skills, while also performing quantitative data analysis with OriginLab and/or MatLab to understand and model the experimentally measured magnetic behaviors.

Entropy-stabilized Cuprate Superconductors, Prof. Ryan Need
        Copper oxide (cuprate) superconductors hold the record for highest superconducting temperature of any material, at ambient pressure. However, that record is still well below room temperature, limiting the application of cuprate superconductors in everyday technology, and there are still gaps in our understanding of these superconductors. The goal of this project is to gain new insight into the physics of cuprate superconductors by introducing a large amount of disorder on specific sites (i.e. atomic positions) in the cuprate's crystal lattice. To do this, we will apply a phenomenon known as entropy-stabilization, which enables the formation of a single, homogenous phase with large disorder by increasing the system's entropy. Entropy stabilization has not yet been achieved for the cuprate superconductors.
        The REU student working on this project will use solid-state synthesis methods (e.g. grinding, pressing, and firing powders) to create samples entropy-stabilized versions of cuprate superconductors based on the prototype YBa2Cu3O7 (YBCO). The student will vary their precursor composition and/or heat treatment, then use powder X-ray diffraction to analyze the crystal structure of their samples and determine relationships between synthesis and the resulting crystal structure. On high-purity samples, the student will collect electrical conductivity and magnetization measurements to determine the material's superconducting behavior and how it depends on the crystal structure and processing.

Plasmonic Nanomaterials for Energy, Environment, and Biomedicine, Prof. Wei David Wei
        The Wei group studies the electronic and optical properties of metallic and semiconductor nanomaterials and their applications in solar energy harvesting, conversion and storage; visible-light photocatalysis; chemical and biological sensing, and photothermal cancer therapeutics. As a specific example, using sunlight to facilitate and promote valuable chemical reactions is an ideal solution to the challenge of meeting future energy demands. Toward that end the Wei group aims to address fundamental questions concerning surface plasmon resonance (SPR)-mediated interfacial electron transfer (ET) and photothermal heating in order to develop new materials and strategies for efficiently converting solar energy to chemical energy. Specifically, they want to unambiguously reveal the mechanics of plasmon-mediated electron transfer (PMET) in Au/TiO2 heterostructures under visible light during in situ operation and directly probe the relaxation dynamics and energetics of the transferred "effective hot electrons" that participate in photocatalytic reactions. They are interested in exploring new strategies for manipulating "hot electrons" for the rational design and construction of a new class of multi-component solar photocatalysts for efficiently producing H2 from water.
        The REU student will work on the synthesis of multiple types of nanoparticles and then use their chemical and physical properties for photocatalysis. In the process they learn both the chemistry and physics of plasmonic nanomaterials.

Modeling Spin-Lattice Coupling in Molecular Magnets, Prof. Xiaoguang Zhang
        Single molecule magnets have magnetic atoms such as Mn which are coupled so as to behave like a single large magnetic moment. Potential applications of single molecule magnets include magnetic bits for data storage and qubits for quantum computers. Prof. Xiaoguang Zhang is studying the spin-lattice coupling in molecular magnets. When the magnetic moment in a molecular magnet changes its orientation, there is a deformation in the positions of the atoms in the molecule.
        The REU will apply computational materials techniques such as the semi-empirical quantum chemistry method to model spin-lattice coupling in molecular magnets. They will also have the opportunity to collaborate with others in his group using density functional theory and machine learning techniques. Some computational experience is preferable for this project. The REU student will learn some modern computational materials modeling techniques and the physics and chemistry of single molecule magnets.

Optical Properties of Two Dimensional Materials, Prof. Xiao-Xiao Zhang
        Two dimensional matirial heterostructures are created by stacking two dimensional materials in different orders and orientations. They can be used to create monolayer semiconductors, magnetic materials, superconductors, and many more exotic materials. In the lab of Prof. Xiao-Xiao Zhang two dimensional heterostructures are grown and probed optically. They study the light-matter interaction and transient dynamics in these nanoscale materials.         The REU student will participate in growing new two dimensional material heterostructures and measure their optical properties. They will learn about the physics of two dimensional materials and their heterostructures. They will also learn first hand how to grow them and make optical measurements on nanoscale materials.