Summer Research Experience for Undergraduates 2025
2025 Summer REU Student Information & Research Projects
Name: Anthony Bencomo Diaz
Undergraduate Institution: Colorado State University Pueblo
Major: Chemistry
REU Advisor: Patrick Woodward
Project Title: A Conductivity Study of BaInO2F:Sn
Abstract: BaInO2F, an oxyfluoride, adopts a cubic perovskite structure, which has a wide band gap. Through this study, we aimed to introduce Sn3+ as a dopant into the In3+ sites in this system to introduce charge carriers for potential wide bandgap semiconductor applications. The samples were prepared by solid-state reactions. Sn doped In203 was synthesized first at high temperature to reduce Sn4+ to Sn3+. The doped In203 is further used to synthesize Ba2In205, the precursor, which is then fluorinated via polyvinylidene fluoride (PVDF), yielding the final products. To allow clean-up of synthesis, X-ray diffraction (XRD) measurements were taken in between each step to monitor the quantity of impurities and decomposition. In combination with XRD, X-ray fluorescence (XRF), and UV-Vis data were collected to provide both elucidation of the elemental composition and conductive potential. Future work includes treating the product under forming gas to ensure the correct oxidation state and determining the excess amount of PVDF needed to ensure complete reaction of the precursor while limiting BaF2 formation.
Name: Vincent Kerler
Undergraduate Institution: University of Pennsylvania
Major: Physics
REU Advisor: Yuan-Ming Lu
Project Title: Defect Response in Delicate Topological Insulators
Abstract: Topological insulators are special materials that act like insulators in their bulk, but host robust conducting surface states that are characterized by bulk properties. This paper investigates dislocation response in a 2-band 2D TI with so-called delicate topology. Delicate topological insulators are characterized by Berry phase differences quantized by 2 between high symmetry lines in reciprocal space. Much of the research into delicate Tis has been theoretical, and not much is known about the effects that defects and other real-world effects from the structure of these materials cause. The specific model tested consists of stacked 1D Su-Schrieffer-Heeger chains with diagonal hopping potentials between the chains. Defects were generated by splicing together two square lattices of unequal size, guaranteeing a mismatch when connecting neighboring sites at the interface between the smaller and larger lattices. Uncoupled sites act as a new surface on the topological insulator and host protected edge modes. Numerical analysis on these modes was conducted in Python and results were compared with analytic solutions.
Name: Breck Lindahl
Undergraduate Institution: Taylor University
Major: Chemistry
REU Advisor: Joshua Goldberger
Project Title: Axis Dependent Conduction Polarity in Zintl Phases
Abstract: Generally semiconductors are considered to have one type of dominant charge carrier along all crystallographic directions, either electrons (n-type) or holes (p-type). However, there is a unique class of materials in which both dominant charge carriers are present along two orthogonal directions inside a single crystal. This phenomenon is referred to as axis-dependent conduction polarity (ADCP). Since many electronic devices, such as LEDs, photovoltaic cells, and transistors, must utilize both n-type and p-type conducting materials to function, the creation of ADCP materials could allow for these devices to function more efficiently utilizing only one crystal as the conduction element. Here, we will demonstrate our recent progress in developing direct band-gap materials that exhibit axis-dependent conduction polarity. First, we start by establishing the band structure origin of ADCP and provide some recent examples from our group that have been experimentally shown to exhibit ADCP. We then thoroughly detail our approache to explore ADCP in the family of AM2Pn2 compounds, where A is Ca, Ba, and Yb, M is Zn and Cd, and Pn is a pnictide. Finally, as direct band-gap materials can be easily optically excited, we will discuss possible applications in photocatalysis or optoelectronics utilizing materials with ADCP.
Name: Austin Merkle
Undergraduate Institution: The University of Texas at Austin
Major: Physics and Mathematics
REU Advisor: Brian Skinner
Project Title: Chiral Spin Order in Wigner Crystals
Abstract: Wigner crystals (WC) are a phase of a low-density electron gas where the electrons form a triangular lattice. The magnetic states of this phase have potential application in spintronics, and understanding the behavior of the spin ordering is an important step to this goal. 2-spin exchange interactions dominate at high electron density. However, previous research has shown that at low electron density, cyclic 3-spin exchange becomes dominant. The competition of these interactions leads to interesting spin orders. In this study, we introduce a Berry phase to the cyclic 3-spin exchange and use classical Monte Carlo simulation and variational techniques to analyze the resulting phase transitions and spin orders, including a Skyrmion-like structure.
Name: Kaitlyn Stewart
Undergraduate Institution: Marietta College
Major: Physics
REU Advisor: Patrick Woodward
Project Title: Synthesis and Characterization of Na3MoO4M and Na3-2xCaxMoO4M (M = F, Cl)
Abstract: In this work, mixed-anions antiperovskites NaMoOF and NaMoO,Cl were synthesized, characterized, and introduced to vacancies for potential ionic conductivity. The host NaMoOF adopted orthorhombic lattice with space group Pnma, while Na,MoOC adopted tetragonal one with P4/nmm. Once these compounds were successfully made, vacancies were introduced into the structures by substituting Ca2+ and Mg2+ at the Na+ sites in the structures to enhance the ion mobility of Na+ cations. All the samples were characterized by X-ray diffraction (XRD) for detailed structural information.
Name: Jason Spada
Undergraduate Institution: California State University Long Beach
Major: Physics and Applied Mathematics
REU Advisor: Lisa Hall
Project Title: How Ring Deletion Impacts the Structure of Interlocked Ring Polymer Sheets as a Function of Solvent Quality
Abstract: Rings of DNA can be interlocked to create chainmail-like sheets, such as those uniquely found in certain organisms called kinetoplasts. Prior studies have explored the topological behavior of these sheets, showing that the type of ring linkage changes the sheet’s preferred shape in solution, with some initial work on how their structure changes with solvent conditions. Here, we investigate how the structural features of the sheets, such as average size and curvature, change as a function of ring removal, and examine how this changes for incomplete sheets (with rings deleted randomly from an initially complete lattice of interlocked rings). Specifically, using coarse-grained simulations that treat the rings as bead-spring chains, we analyze the structure’s radius of gyration and shape in implicit solvent of various effective solvent qualities.
Name: Maggie Van Someren
Undergraduate Institution: University of Minnesota Twin Cities
Major: Materials Science and Engineering
REU Advisor: Roland Kawakami
Project Title: Epitaxial growth and magneto-optic measurements of 2D van der Waals magnet / topological insulator heterostructures
Abstract: Two-dimensional van der Waals (2D vdW) magnets offer highly tunable magnetic properties up to the atomic limit. Because of their small magnetic volume and magnetically live interfaces, they are being explored to advance the miniaturization of electron-spin-based electronics (spintronics) devices. An emergent method to manipulate such devices is by harnessing spin-orbit torque, offering the potential to significantly enhance energy efficiency and switching speeds compared to traditional magnetic memory technology. In this study, bilayers of 2D vdW magnets Cr2Ge2Te6 (CGT) and Fe3GeTe2 (FGT) with topological insulator Bi2Te3 (BT) are grown via molecular beam epitaxy. The structure and stoichiometry of the films are verified using reflection high-energy electron diffraction and X-ray diffraction. The magnetic signal of the films is determined by magnetic circular dichroism measurements. The next step is to measure the current-modulated magneto-optic Kerr effect on a CGT/BT bilayer to quantify the spin-orbit torque efficiency, with applications for faster, more efficient magnetic memory storage.
