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.
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.