Previous APMS Colloquia
Fall 2025
Thursday,October 16, 9:45-10:45 am
Dr. Xin Chang
University of Texas at Austin
Excitation Pathways in π-Conjugated Crystals: From Frenkel-CT mixing to singlet fission
Abstract: Organic crystals host tightly bound excitons with tunable couplings and rich spectral behavior. Slip-stacked donor–acceptor–donor (DAD) aggregates exhibit red- shifted J- and H-type spectra that contradict Kasha’s Coulomb-coupling picture. Using vibronic exciton models, it will be shown that intermolecular charge transfer (ICT) controls aggregate type: in-phase ICT yields J-behavior, out-of-phase yields H-behavior, with clear vibronic diagnostics. An efficient effective Frenkel–Holstein formulation reproduces the lowest absorption band and photoluminescence in 2T-DPP-2T films and nanoparticles, explaining the red-shifted H-aggregation at reduced computational cost. This framework is then extended to CT-mediated singlet fission in slip-stacked crystals, where the phases of Frenkel–CT and CT–TT couplings determine the symmetry of electronic wavefunction (symmetric vs. antisymmetric)-and thus which TT states are bright or dark; vibronic coupling preserves symmetry but tunes the A 1 /A 2 ratio in line with the ratio rule. The theory matches spectra for two EP-PDI crystal phases, offering practical design rules for DAD aggregates and SF-active PDI materials. We connect model parameters to DFT, and outline design rules for singlet-fission-enabled materials and heterojunctions.
Bio: Dr. Xin Chang is a postdoctoral fellow in the McKetta Department of Chemical Engineering at The University of Texas at Austin. He earned his Ph.D. in Physical Chemistry from Temple University and his B.S. in Chemistry from Nankai University. His research centers on exciton physics in organic semiconductors and two-dimensional materials (e.g., MoS₂). He combines vibronic exciton theory with ab-initio calculations to explain optical spectra— including red-shifted H-aggregation in donor–acceptor–donor stacks and charge-transfer–mediated singlet fission in PDI crystals—informing the design of next-generation optoelectronic materials.
Thursday,October 2, 9:45-10:45 am
Prof. Dan Wasserman
University of Texas at Austin
Engineering Infrared Optical Response at Spatial and Temporal Extremes
Abstract: The mid-infrared (mid-IR) spectral range (loosely defined as the wavelengths between 3- 30µm) is a vital wavelength range for a host of sensing, imaging, and even communication applications. Reducing the dimensions of optical devices and structures operating in the mid-IR, specifically to the nano-scale, is exceedingly challenging, due to the diffraction limit. However, there exist significant potential benefits to such scaling, not solely in terms of size, weight, and power requirements, but also in intrinsic device performance. This presentation will describe approaches for enhancing light-matter interaction in ultra-subwavelength thin films, structures, and devices for polarization, angle, and wavelength selective absorption, emission, and non-linear response in the mid-infrared. First, I will discuss light-matter interaction at the ultimate limits of material thickness. Using this formalism, I will show recent work demonstrating perfect absorption in ultra-subwavelength films, and how we can use these structures for sub-picosecond nonlinear response across a range of infrared wavelengths. I will then discuss our groups work in mid-IR plasmonics, leveraging both doped semiconductors and metaplasmonic films. I will focus on the new field of metaplasmonics, and show how we can achieve extreme mode confinement, waveguiding, and even hyperbolic response in engineered metal films only hundredths of a wavelength thick. Ultimately, I hope to demonstrate that the mid-IR provides a unique materials playground for the exploration, and implementation, of a range of light-matter interactions.
Thursday, September 25, 9:45-10:45 am
Prof. Allison Fish
University of Queensland
Facilitating a Responsible Quantum Community: Navigating Authorship and Inventorship Discussions in a Multi-disciplinary Scientific Team
Abstract: Launched in late 2023, the ARC Centre of Excellence in Quantum Biotechnology (QUBIC) is a 7 year interdisciplinary research collaboration that aims to develop paradigm shifting quantum technologies for the enhanced observation of biological processes, thus transforming our understanding of the life sciences. An innovative part of QUBIC’s larger goal is the integration of a ‘responsible science’ program that focuses on a defined set of social, legal, and regulatory issues arising at the intersection of quantum and the life sciences. In this talk I will begin by giving an overview of the responsible science program and then take a closer look at our qualitative social science work on how authorship and inventorship determinations are navigated in multi-disciplinary science. I will then facilitate a brief workshop on this topic.
Bio: Allison Fish is an associate professor in the Law School and a Principal Research Fellow with the Centre for Policy Futures at the University of Queensland in Brisbane, Australia. As Chief Investigator with the ARC Centre of Excellence in Quantum Biotechnology, Allison leads the responsible science research program. A key question that has directed much of Allison’s work is: What are the legal forms, technological infrastructures, and cultural logics that shape information/knowledge management practices? Prior to joining UQ, Allison was an assistant professor of Social Informatics at Indiana University.
Spring 2025
Thursday, May 1, 9:45-10:45 am
Prof. Christian Arenz
Arizona State Univ.
Speeding Up Quantum Dynamics Through Parametric Control
Abstract: Strong interactions between the components of a quantum system are critical for leveraging quantum effects for quantum technologies. In this
talk, I present a protocol to enhance such interactions through control, thereby speeding up the system’s evolution without knowing parameter
details. I first show that while this is impossible for systems with finitely many degrees of freedom, interactions involving quantum harmonic oscillators can
generically be enhanced through local parametric control of high frequency. I go on to discuss phase insensitive amplification of displacements,
enhancing Jaynes-Cumming type interactions, and speeding up the implementation of quantum logic gates as potential applications of the
presented control strategy. Finally, I report the experimental realization of the protocol in an ion trap system and discuss further applications in photonic quantum computing.
Thursday, April 17, 9:45-10:45 am
Dr. Sergei A. Ivanov
Los Alamos National Laboratory
Colloidal Routes to Nanomaterials with Various Functionalities
Abstract: Recent advances in low-dimensional materials have opened new pathways for designing functional materials with tailored electronic, magnetic, and catalytic properties. As part of the User Program at the Center for Integrated Nanotechnologies (CINT), this talk will highlight two distinct but conceptually linked projects that utilize colloidal route to nanostructured materials with emergent functionalities. The first project explores colloidal routes to two-dimensional ferromagnetic Cr-Te nanosystems. While intrinsic 2D ferromagnets such as Cri, support long-range magnetic ordering down to the few-layer limit, their low Curie temperatures limit practical use. In contrast,
the Cr-Te system offers a rich phase diagram with numerous stable and metastable stoichiometries exhibiting higher Curie temperatures,
in some cases approaching room temperature. Despite growing interest, solution-phase methods for synthesizing these materials remain limited. I will show a colloidal path to several nanoscale Cr, Te, phases and extend this approach to the ternary CrGeTe system, offering a viable alternative to solid-state methods. The second project focuses on developing low-cost, high-performance electrocatalysts for oxidation reactions, including the oxygen evolution reaction (OER), a key step in electrolytic hydrogen production. Industrial OER catalysts typically rely on scarce, expensive materials such as RuO, and IrO. I present a low-temperature colloidal synthesis (<300°C) of transition metal nitride (TMN) nanoparticles-specifically mono- and bimetallic Fe- and Ni-based M3Nx phases- from molecular cluster precursors and mild nitrogen sources. This approach enables control over particle size, shape, and surface morphology, yielding TMNs with OER activity comparable to commercial RuO and IrO under alkaline conditions. Together, these projects demonstrate how solution-phase synthetic strategies can enable access to novel nanomaterials for both quantum materials research and sustainable energy technologies.
Thursday, April 3, 9:45-10:45 am
Dr. Alan Van Orden
Colorado State University
Time-Resolved Super-Resolution Localization Microscopy to Image Photoluminescence Lifetimes and Energy Transport in Semiconductor Quantum Dots Patterned on DNA Origami
Abstract: Time-resolved super-resolution localization microscopy is a technique to image photoluminescence lifetimes and other optical properties of nanoscale emitters with nanosecond time resolution and nanometer spatial resolution. This presentation will discuss the application of this technique to image multi-emitter semiconductor nanostructures. In some cases the proximity of the emitters gives rise to electronic energy transport pathways that can be directly imaged using this technique. To form the multi-emitter nanostructures, we pattern semiconductor quantum dots onto spatially addressable DNA origami. Combining this super resolution microscopy with other nanoscale microscopies (e.g. atomic force and electron microscopy) reveals the optical properties of each individual quantum dot, as well as the structural information about the relationships between the energy transport properties of the emitters and the structural arrangements of the nanoparticles. Applications of these methods to characterize the optoelectronic properties of nanoscale devices, such as light emitting diodes, will be discussed.
Professor Alan Van Orden received his B.S. in Chemistry from Brigham Young University in 1990 and his Ph.D. in Physical Chemistry from the University of California at Berkeley in 1996. His Ph.D. research was supervised by Richard J. Saykally and focused on the structure and spectroscopy of carbon and silicon-carbon clusters in the gas phase and the interstellar medium. From 1996-1999 he was a postdoctoral research associate working on biomedical applications of single molecule fluorescence detection and spectroscopy with Richard A. Keller at Los Alamos National Laboratory. In 1999 he joined the Chemistry faculty of Colorado State University where he has been ever since. His research pursuits involve development and applications of novel techniques for single molecule detection, spectroscopy, and imaging. He has been a visiting scientist at Stanford University, University of Missouri, Los Alamos National Laboratory, Air Force Research Laboratory, and Naval Research Laboratory.
Thursday, March 20, 9:45-10:45 am
Dr. Edward Yu
University of Texas at Austin
Semiconductors for Quantum and Sustainable Energy Applications
Abstract: Semiconductor materials are foundational to technologies ranging from computing to communications to renewable energy. In nearly all cases, control over structure and electronic properties at or near the nanometer scale is essential. However, the dimensions over which such control must be exercised can vary dramatically – from nanometers to meters or larger. We will discuss a variety of recent projects in our laboratory in which semiconductor material and device properties must be controlled or characterized at or near nanometer length scales, but for which the relevant scale for useful application ranges from microns to meters or larger. First, we discuss studies of monolayer transition metal dichalcogenide semiconductors, in which single photon emission can be observed in the presence of tensile strain. We show how proximal probe measurements with a back-gated sample geometry allow the full strain tensor of monolayer transition metal dichalcogenide semiconductors to be measured with spatial resolution of tens of nanometers [1]. These studies provide insight into actual nanoscale strain configurations in geometries for which single photon emission is typically observed, and also enable characterization of phenomena such as piezoelectricity at the nanoscale. We then discuss studies in which strain can be controlled dynamically via electrostatically induced deflection of monolayer WSe2 membranes, an approach with the potential to enable electrical control over single photon emission. In the second part of the presentation, we discuss a variety of approaches for exploiting concepts and processes from the realm of semiconductor manufacturing and device physics – band structure engineering, resistive switching, and nanoscale thin-film reactions – to fabricate photoelectrodes for solar-powered splitting of water molecules into hydrogen and oxygen [2-4]. Our recent results in this area suggest an approach for creation of photoelectrodes for green hydrogen production with scalability and costs similar to those for silicon photovoltaics, thereby offering intriguing prospects for cost-effective green hydrogen production, i.e., production of hydrogen without
carbon dioxide emissions.[5] Such advances could help mitigate the over 900 million tons of carbon dioxide generated annually by current methods of commercial hydrogen production that serve a global market for hydrogen of over $170 billion annually.
[1] Nano Lett. 3c03100 (2024).
[2] Nature Nanotechnol. 10, 84 (2015).
[3] Nature Mater. 16, 127 (2017).
[4] Nature Commun. 12, 3982 (2021).
[5] ACS Appl. Energy Mater. 4c00016 (2024).
Edward Yu is Professor of Electrical & Computer Engineering and holds the Judson S. Swearingen Regents Chair in Engineering at the University of Texas at Austin. He received his A.B. (summa cum laude) and A.M. degrees in Physics from Harvard University in 1986, and his Ph.D. degree in Applied Physics from the California Institute of Technology in 1991. He was a postdoctoral fellow at the IBM Thomas J. Watson Research Center from 1991 until 1992, and a faculty member at the University of California, San Diego from 1992 until 2009, when he assumed his current position at the University of Texas. Professor Yu has been the recipient of an NSF CAREER Award, ONR Young Investigator Award, Alfred P. Sloan Research Fellowship, UCSD ECE Graduate Teaching Award, and UT Austin Lepley Memorial Teaching Award, and is an AVS and IEEE Fellow. He has served as a member and chair of the DARPA Defense Sciences Research Council (DSRC), and currently serves at UT Austin as founding Director of the Center for Dynamics and Control of Materials: an NSF MRSEC. Current research interests in his laboratory include photovoltaics and other technologies for energy harvesting and generation; nanoscale imaging and characterization techniques; and solid-state nanoscience and nanotechnology generally. The results of his research have been reported in over 220 archival journal publications and over 300 conference and seminar presentations.
Thursday, February 20, 9:45-10:45 am
Prof. Naomi Lee
NAU
Designing Vaccines to Target Chronic and infectious Diseases in Native American Communities
Abstract: At the national level, opioid overdoses are among the leading causes of death across the United States especially within Native American communities. Vaccines may pose as a possible treatment for addiction and prevention of overdoses. Virus-like particles (VLPs) have multi-valent displays and mimic the conformation of certain native viruses but lack a viral genome, making them noninfectious. A derivative of oxycodone was conjugated to pre-formed Qβ VLPs, and intramuscular immunization with Qβ-oxycodone elicited high-titer, high-avidity and long-lasting antibody responses in mice. Pilot studies also showed the Qβ-oxycodone is immunogenic in nonhuman primates. These data establish Qβ-oxycodone as a promising opioid vaccine candidate.
As one of the only Native Americans to receive a PhD in 2013, Dr. Lee strives to change this story for the next generation of Native American students through incorporating the teachings of my Haudenosaunee (Iroquois) ancestors into her science and mentorship. Dr. Lee will discuss obstacles and successes throughout her academic journey and military career along with how these experiences shaped her career goal of improve Native American health through research, STEM education, and mentoring.
Thursday, February 6, 9:45-10:45 am
Prof. Chris Mann
NAU
Advances in Digital Holography: From FINCH Imaging to Biological Applications and Phase Retrieval
Abstract: Optical interferometry remains a fundamental and versatile tool in both scientific research and industrial applications, enabling high-precision, non-contact measurements across a range of fields. From common consumer devices such as hard disk drives, optical storage systems, and cameras to advanced applications in semiconductor metrology, biomedical imaging, and materials characterization, interferometry provides unparalleled accuracy, often reaching nanometer or even sub-nanometer precision. Holography, a key branch of interferometry, extends these capabilities by capturing both the intensity and phase of light waves, enabling full-field 3D imaging and quantitative phase contrast. With the advent of digital holography, traditional photochemical holography has been replaced by high-resolution sensor arrays and real-time computational processing. This transition and the introduction of high-resolution spatial light modulators which can act as a digital lens, has enabled new imaging modalities such as Fresnel Incoherent Correlation Holography (FINCH), which allows incoherent light sources to be used for holographic imaging, expanding the applicability of holography beyond coherent laser illumination. In this presentation, I will provide an overview of digital holography, including its evolution from classical optical interferometry to newly developed computational techniques. I will discuss its application in biological imaging, where digital holography enables label-free visualization of live cells and tissues, and in materials characterization, where it plays a critical role in detecting surface defects and structural deformations. Additionally, I will explore recent advances in phase retrieval algorithms, which have enhanced holographic reconstruction by improving resolution, noise robustness, and computational efficiency.