CM/BIO/ECE Seminars

The combined Condensed Matter/Biological Physics/Electrical and Computer Engineering Seminars take place every Wednesday at 4 PM in the Physics Library (rm 223A, Physics Bldg.)

2024
Spring Semester
Date Speaker/Title/Abstract
4/17/24 Dr Damon Farmer
CM Seminar
4/16/24 Dr Damon Farmer
CM Seminar
4/10/24 Prof. Saisudha Mallur, West Illinois University
TBA

TBA

2/21/24 Dmitry Ovchinnikov
Van der Waals Topological Magnets and Superconductors

Abstract: The breaking of time-reversal symmetry in topological insulators leads to novel quantum states of matter. One prominent example at the two-dimensional limit is the Chern insulator, which hosts dissipationless chiral edge states at sample boundaries. These chiral edge modes are perfect one-dimensional conductors whose chirality is defined by the material magnetization and in which backscattering is topologically forbidden. Recently, van der Waals topological magnet MnBi2Te4 emerged as a new solid-state platform for studies of the interplay between magnetism and topology. In this talk, I will present an overview of our progress toward controlling topological phase transitions and chiral edge modes in MnBi2Te4 as well as discovering new quantum states in this material family. First, I will establish how topological properties are intimately intertwined with magnetic states. I will then demonstrate electrical control of the number of chiral edge states and the discovery of chiral edge modes along crystalline steps between regions of different thicknesses and how these modes can be harnessed for the engineering of simple topological circuits. Finally, I will discuss the engineering of the superconducting state in topological insulators and demonstrate Pauli paramagnetic limit violation in atomically thin flakes of a topological superconductor candidate.

Bio: Dmitry Ovchinnikov earned his Ph.D. from the Institute of Electrical and Micro Engineering at École Polytechnique Fédérale de Lausanne (EPFL), Switzerland in 2017. During his Ph.D., he conducted experiments on two-dimensional semiconductors and developed techniques to modulate disorder in low-dimensional systems. His thesis earned him the EPFL EDMI PhD thesis distinction award and the Gilbert Hausmann PhD thesis award. He received an early postdoc Swiss National Science Foundation (SNSF) mobility fellowship to research nanoscale van der Waals magnetic devices at the University of Washington with Prof. Xiaodong Xu. Currently, Dmitry is an Assistant Professor at the Department of Physics and Astronomy at the University of Kansas. His work involves exploring the fundamental physics and applications of topological magnets, superconductors, and correlated states in low-dimensional quantum materials.

2/14/24 Prof. Symeon Mystakidis
CM Seminar

“Phases and dynamics of dipolar gases and universality of ferromagnetic superfluids” 

This presentation consists of two separate parts. In the first, we will discuss the static properties and the dynamics of dipolar Dysprosium Bose-Einstein condensates subjected to a fastly rotating external magnetic field. The underlying phase diagram with respect to the atom number and relative interaction strengths for various field orientations is mapped out. Transitions  from a superfluid to a supersolid and then to arrays of dipolar droplets characterized by a non-vanishing global phase coherence will be elucidated. Following quenches, across the aforementioned phase transitions, we observe the dynamical nucleation of supersolids or droplet lattices. Three-body losses lead to self-evaporation of the ensuing structures, while the rotating magnetic field enables, for fixed values of the relative interactions, an enhancement of the droplet lifetimes. The second part will be devoted to  address universality in the non equilibrium dynamics of a two-dimensional ferromagnetic spinor gas subjected to modulations of the quadratic Zeeman coefficient. For short timescales we observe the spontaneous nucleation of topological defects (spin-vortices) which annihilate through their interaction giving rise to magnetic domains deeper in the evolution where the gas enters the universal coarsening regime. This is characterized by the spatiotemporal scaling of the spin correlation functions and the structure factor allowing to measure corresponding scaling exponents which depend on the symmetry of the order parameter and belong to distinct universality classes. These results represent a paradigmatic example of categorizing far-from-equilibrium dynamics in quantum many-body systems and reveal the interplay of topological defects for the emergent universality class.

2/7/24 Prof. Wendel Alves from UFABC in Sao Paulo, Brazil
Peptide-Based Building Blocks: Advancing Supramolecular Catalysis and Electronic Integration in Biosensor Applications

Abstract: Self-assembling peptides have emerged as a cutting-edge class of materials that can be engineered to form one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) nanostructures, with diverse potential applications in bioimaging, tissue engineering, controlled drug delivery, and as catalysts and sensitive elements in biosensors. These peptide compounds are highly versatile molecular building blocks, attributable to their rich chemical diversity and inherent affinity for biological interfacing. The functionalization of these nanomaterials with nanoparticles of transition metals, conjugated polymers, and photoluminescent compounds has expanded their application range within nanotechnology. Moreover, organized systems of peptides have shown significant promise in asymmetric catalysis, particularly in aldol reactions, offering a novel route for synthesizing optically active compounds. This seminar primarily focuses on designing peptide-based materials for asymmetric catalysis and constructing biomimetic systems, emphasizing applications in biosensor devices.

 

Wendel Andrade Alves is a Full Professor at the Federal University of ABC, Brazil, and a Research Fellow of the Brazilian National Council for Scientific and Technological Development (CNPq), Level 1B. He has a Ph.D. in Chemistry from the University of São Paulo, Brazil, where he also completed a Post-Doctoral fellowship in Physical Chemistry at the Laboratory of Electroactive Materials. His research interests involve the supramolecular assembly of natural and synthetic polymers, the self-assembly of peptides, and biosensor development.
 

2023
Fall Semester
Date Speaker/Title/Abstract
11/15/23 Dr. Jaewon Lee
CM Seminar
10/25/23 Junyeong Ahn, Harvard University
Exploring optical material properties through quantum geometry

Understanding and manipulating quantum superposition are important quests in quantum materials research. One exciting direction emerging in the field is to use the geometry of quantum states – the so-called quantum geometry – as a means of characterizing quantum superposition. This approach has successfully characterized various electric and magnetic properties of materials, which are not easily captured by semiclassical approaches. In this seminar, I will first introduce a general theory of the quantum geometry of resonant optical electric-dipole responses in materials. I will discuss the new insights from this quantum-geometric paradigm, guiding us to discover and investigate new optical phenomena. In the second part, I will talk about an intriguing optical response going beyond electric-dipole transitions: a surprising Kerr effect in certain antiferromagnets that are non-quantized but owe their existence to axion electrodynamics. This response has recently been observed in experiments and used for the optical control of antiferromagnets. Finally, I will give an outlook for future directions.

10/11/23 Prof. Halyna Hodovanets, Missouri S&T
Inversion and time-reversal symmetry broken Weyl semimetal

Weyl semimetals are among the materials proposed to have significant potential in informational technologies and to harbor the necessary elements for quantum computing. They host Weyl nodes at specific points in their Brillouin zone, a pair of relativistic fermions with different chirality, Weyl fermions. The nontrivial momentum-space topology due to the Weyl nodes leads to various fascinating phenomena, such as the chiral anomaly, chiral magnetic effect, anomalous magnetoresistance and Hall effect, large nonsaturating thermoelectric power and ultrafast photocurrents just to name a few. The essential ingredients for the realization of the Weyl semimetal are the absence of inversion symmetry and/or time-reversal symmetry. The RAlX (where R=Rare Earth and X=Ge, Si) family, where both symmetries are broken, has been recently identified as a large class of Weyl semimetal based on systematic first-principles band structure calculations and APRES measurements. In this respect, I will present details and importance of crystal growth of non-centrosymmetric CeAlGe single crystals, their physical properties, anomalous magnetotransport, and discuss the future implications of our findings and the tunability of RAlGe and RAlSi families.  

Spring Semester
Date Speaker/Title/Abstract
4/19/23 Dr. Min Su, Director of The Center for Electron Microscopy, University of Missouri
Cryo-EM Sample to Structure Pipeline @MU

Cryo–electron microscopy (cryo-EM) has been proven a powerful tool visualizing biological specimen. Method developments in single-particle analysis (SPA) and in situ tomography have enabled more structures to be imaged and determined to attenable resolutions. Sample-to-structure pipeline is essential for an imaging Core in improving the productivity and efficiency in structural determination. As the Director, I am leading the MU Electron Microscopy Core (EMC) in collaboration with MU research laboratories from Physics, Material Science, Computer Science, Biochemistry etc. to develop and implement such a unique pipeline housed in NextGen. Cryo-EM will continue its remarkable growth in technology advancement in the next decades. MU provides great centralized microscopy resource at EMC for scientists from all fields to advance their career and research. We welcome collaborations. 

4/11/23 Sang-Hoon Bae from Washington University in St. Louis
Material Innovation through Freestanding Nanomembranes towards Future Electronics

Abstract:

The conventional electronic system has been developed upon Si-based thin-films because of their cost-effectiveness and mature process. However, there are fundamental limitations in using conventional systems towards future electronics such as wearable devices, biomedical devices, and edge computing devices. One of these most prevalent limitations is that current thin-film electronic systems have been developed on rigid wafers, which causes serious physical constrains because of the thick nature of the materials on the rigid wafers. Thus, an alternative approach has been required to secure mechanically low stiffness of materials and devices.

In this talk, I will discuss about our recent effort to tackle the aforementioned challenge by developing 3D and 2D freestanding nanomembranes. First of all, we have conceived an approach to obtain freestanding single crystalline materials through 2D materials assisted layer-transfer (2DLT). While developing it, we found out that crystallographic information can penetrate through graphene as long as substrates have polarity because of graphene’s information transparency. Also, the slippery nature of graphene enables spontaneous relaxation, which substantially reduces dislocation density in heteroepitaxy. Second, we have developed mechanics to produce 2D materials by playing interfacial toughness contrast. As this approach allows producing various 2D materials at large-scale, various applications can be demonstrated at practical level. Also, we realized that geometrical confinement helps kinetic control of 2D materials, which secures crystallinity, layer-controllability, and heterostructures. As the 3D and 2D freestanding membranes are a new type of building blocks, various opportunities are expected by providing a new platform where physical couplings and practical applications are conceived.

Bio:

Sang-Hoon Bae is an Assistant Professor in Washington University in St. Louis. He was a postdoctoral research associate at Massachusetts Institute of Technology (MIT) working with Professor Jeehwan Kim before joining Washington University. He earned a doctorate in materials science and engineering from University of California, Los Angeles (UCLA) under the supervision of Professor Yang Yang in 2017. He earned bachelor's and master's degrees in materials science and engineering from Sungkyunkwan University (SKKU), Korea, under the supervision of Professor Jong-Hyun Ahn in 2013. He worked at IBM T. J. Watson Research Center (2014) and Samsung Display (2010) as a research intern. He has published more than 70 papers in notable journals including Science, Nature, PNAS, Nature Materials, Nature Nanotechnology, Nature Photonics, and Nature Electronics with over 8000 citations. His h-index is 41 as of March 2023. 

3/15/23 Bryce Sadtler
Nanoscale Imaging of Catalytic Activity in Semiconductor Nanostructures Using Single-Molecule Fluorescence Microscopy

Abstract:

Semiconductor nanocrystals are promising candidates for generating chemical feedstocks through photocatalysis in which photoexcited charge carriers are used to perform charge-transfer reactions. However, the fate of photoexcited charges once they reach the surface, i.e., whether they recombine or are extracted to initiate useful redox reactions, is highly sensitive to the structure of the surface. Our research group is investigating how oxygen vacancies, a common type of surface defect in metal oxide semiconductors, control their photocatalytic activity. Using single-molecule, super-resolution fluorescence microscopy, we image both spatial and temporal variations in the photocatalytic activity of individual semiconductor nanocrystals such as bismuth oxybromide and tungsten oxide. To understand the chemical origins of these variations in activity we apply a combination of ensemble structural characterization, electronic-structure calculations, and the quantitative spatial correlation of multiple fluorogenic probes. Our results show that both photoexcitation and chemical modifications to the surface of semiconductor nanocrystals can be used to tune the concentration and distribution of oxygen vacancies in these materials, which has a significant impact on their resulting catalytic activity. In one system, bismuth oxybromide, a high concentration of oxygen vacancies decreases activity, while in tungsten oxide, it increases activity. Thus, to achieve high performance for a desired catalytic transformation, our results demonstrate it is necessary to tune the concentration and type of defects for the specific photocatalyst. Ultimately, photocatalysts containing a stable, intermediate concentration of oxygen vacancies may prove to be optimal for balancing the activity of both reductive and oxidative transformations in a system that generates chemical fuels from sunlight.

Bio: Bryce Sadtler graduated from Purdue University in 2002 with a B.S. degree in Chemistry. He conducted his graduate studies at the University of California, Berkeley under the guidance of Paul Alivisatos and received a Ph.D. in Physical Chemistry in 2009. He was then a Beckman Institute Postdoctoral Fellow at the California Institute of Technology, where he worked with Nathan Lewis and Harry Atwater. Bryce joined the Department of Chemistry at Washington University in St. Louis in 2014. His research interests include solid-state chemistry and light–matter interactions in nanoscale materials for applications in solar energy conversion and catalysis. He has received an NSF Career award (2018), an ACS PRF Doctoral New Investigator Award (2017), and was named an Emerging Investigator by the Journal of Materials Chemistry (2017). Bryce was promoted to an Associate Professor at Washington University in July 2022.

3/1/23 Prof. Farhana Tuli
Realization of surface properties of two-dimensional material on metal substrate: A step towards wonder material for future applications

Abstract:

Surfaces and interfaces, also referred to as phase boundaries, play an important role in material performance for the application in nanodevices. When the surface of a material comes in contact with another phase, interaction occurs at the interface between the phases which initiates the alteration of properties at the phase boundaries. Therefore, the analysis of the surface properties plays a crucial role in understanding the fundamental insights of crystal growth, reaction kinetics and basis for engineering the nanoparticles as well as interpreting the quantum physics and resolving the theoretical prejudice.


Two-dimensional (2D) materials have drawn enormous research interests due to their intriguing physical properties along with potential applications in the next generation nano-devices. The growth of some 2D materials, such as, Xenes, requires supporting substates which have strong impact on the formation of these materials and their properties. Hence, investigating the surface properties of these types of 2D materials has become quite essential. Recently invented 2D boron (B) sheet which is known as borophene, is considered as a promising material; consists of B atoms arranged in triangular lattice with hollow hexagons. The synthesis of 2D B sheet is still challenging and strongly dependent on the supporting substrates and their crystalline faces, and other factors including temperature, deposition rate etc. during preparation. It is evident from surface analysis by Low energy electron diffraction (LEED), Scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) in ultra-high vacuum (UHV) condition that completely different types of B structures are formed on transition metal substrates with different crystalline faces. The dependency of B growth on substrates creates the opportunities to realize the best substrate for the growth of 2D B sheet which can be employed in future applications.

2022
Fall Semester
Date Speaker/Title/Abstract
11/16/22 Dr. Bernadette Broderick
CP-ICE: A New Tool for Laboratory Studies of Interstellar Ice Chemistry

Zoom link available upon request- email sekhrn@missouri.edu

Abstract:

A new instrument is described that employs buffer gas cooling with mm-wave rotational
spectroscopy to probe molecules desorbed from interstellar ice analogues. The unique
combination of these tools has shown, for the first time, direct measurement of products formed
and desorbing from astrochemical ice analogues with both isomer and conformer specificity, and
determined their relative abundances under well-defined, astrochemically-relevant conditions.
Details of the technique, apparatus, and first results will be described in application to the
temperature-programmed desorption of n- and i-propyl cyanide with rotational spectroscopic
detection. This approach represents a new window into the emergence of chemical complexity in
star forming regions.

11/9/22 Prof. Haiming Wen
Enhanced irradiation tolerance of steels via nanostructuring

Abstract

         Steels have important applications in current and advanced nuclear reactors, however, their irradiation tolerance and mechanical properties need to be improved. Bulk ultrafine-grained and nanocrystalline metals possess drastically higher strength than their conventional coarse-grained counterparts due to significant grain boundary strengthening, and are anticipated to have significantly enhanced irradiation tolerance owing to the role of grain boundaries as sinks for irradiation-induced defects. In our 7-year-long and multi-million-dollar DOE project, ultrafine-grained and nanocrystalline austenitic and ferritic steels were manufactured by equal-channel angular pressing (ECAP) and high-pressure torsion (HPT), respectively. The microstructure and mechanical behavior of the steels manufactured by ECAP and HPT were carefully studied. The thermal stability of the ultrafine-grained and nanocrystalline steels was also investigated. For ferritic FeCrAl alloys with different ranges of grain sizes, thermal aging was conducted to study thermally induced α’ Cr precipitation, which typically causes embrittlement. Neutron irradiation was performed to study irradiation behavior of the steels. Ion irradiation was also conducted to compare with the neutron irradiation. Results indicate that the ultrafine-grained and nanocrystalline steels manufactured by ECAP and HPT possess significantly improved hardness/strength compared to their conventionally manufactured coarse-grained counterparts. In FeCrAl alloys, with decreasing grain size, thermally induced α’ Cr precipitation was reduced. In 304 and FeCrAl steels, smaller grains possess reduced irradiation-induced hardening, segregation and precipitation compared to larger grains. Ultrafine-grained and nanocrystalline 304 steels have enhanced phase stability during irradiation compared to the coarse-grained counterpart. These results indicate enhanced irradiation tolerance of ultrafine-grained and nanocrystalline steels.

  

Bio

          Dr. Wen is an Assistant Professor in Department of Materials Science and Engineering and Department of Nuclear Engineering and Radiation Science at Missouri S&T. He obtained his PhD from University of California – Davis in 2012, and subsequently held postdoctoral appointments at Northwestern University and Idaho National Laboratory. Prior to joining Missouri S&T, he was a Research Assistant Professor at Idaho State University and a staff scientist at Idaho National Laboratory. Dr. Wen has extensive experience in research and development of advanced materials, including those for nuclear applications. He has been leading multiple research projects funded by Department of Energy, National Science Foundation, and Nuclear Regulatory Commission. Dr. Wen has authored or coauthored more than 65 peer-reviewed journal publications, with citations >3,200 and an h-index of 24. He serves on the Editorial Board of the journal Materials Science and Engineering A, and has served as the lead guest-editor of a special issue in AIMS Materials Science. He regularly reviews manuscripts for many journals and research proposals for DOE and NSF.