Physics Colloquium - Spring 2022

Speaker: Stephen B. Cronin, University of Southern California

Abstract: Our research spans a broad range of topics from photocatalysis for solar energy storage (i.e., solar fuels) to thermoelectric energy conversion (i.e., waste heat recovery), and more recently pollution remediation and pollution control devices for treating diesel engine exhaust (i.e., NOx, SOx, and particulate matter (i.e., soot)). I will report our latest results in these research areas with an emphasis on how nanostructured materials and devices can be used to provide new alternative approaches to these age-old problems. For thermoelectric energy conversion, we use 2D layered materials, which have ultra-low thermal conductivity and exhibit charge density waves (CDW) transitions to improve thermoelectric performance. For photocatalysis, we use a plasmon resonant nanostructures to couple light from the far-field to the near-field and promote the injection of hot electrons at the electrode surface. These plasmonic nanostructures provide surface-sensitive spectroscopy of molecules and ions at these electrode surfaces, which can be collected in situ under work electrochemical conditions for both water splitting and CO2 reduction reactions. Lastly, we use nanosecond high voltage pulses to create a transient plasma for pollution remediation. New strategies for producing enhancement in this plasma generation and utilization using metal nanoparticles will be discussed.

Bio:  Stephen B. Cronin received his B.S. in physics from NYU and PhD in physics from MIT in 2002 under supervision of Professor Mildred Dresselhaus followed by post-Doctoral research in Professor Michael Tinkham’s lab at Harvard University. Professor Cronin carried out his post-Doctoral research on the topic of single molecule spectroscopy and electron transport of carbon nanotubes in Professor Michael Tinkham’s lab at Harvard University. Professor Cronin joined the Ming Hsieh Department of Electrical Engineering-Electrophysics at the University of Southern California in August 2005 and has earned several awards for his research accomplishments, including the NSF CAREER Award in 2009, the AFOSR Young Investigator Award in 2008, the Charles Lee Powell Foundation Research Award in 2006, and the James H. Zumberge Research and Innovation Award. Professor Cronin is also an active member of Institute of Electrical and Electronics Engineers, American Association of Advancement of Science, American Physical Society and Materials Research Society.

Speaker: Antonio Pich, IFIC, University of Valencia

Abstract: The replication of the elementary constituents of matter in three fermionic families is one of the more puzzling aspects of our current description of the microscopic world. In the Standard Model, the three families have identical gauge interactions and only differ in their couplings to the Higgs field that generate the observed diversity of masses. This picture has been challenged by a series of anomalies emerging from recent flavour data, which suggest that the interactions of the three known leptons (electron, muon and tau) could be slightly different. An overview of the current status will be presented.

Speaker: Thøger Emil Juul Rivera-Thorsen, Stockholm University

Abstract:

Speaker: Mireia Montes, Space Telescope Science Institute

Abstract: There is a huge amount of astrophysical events that remain barely studied due to the lack of large, multiwavelength and deep optical surveys. This is the Universe at the lowest density of stars, largely unseen by past large field surveys like the Sloan Digital Sky Survey (SDSS). For instance, only a handful of galaxy clusters have been observed with enough depth to witness the intracluster light (ICL), made up of stars that drift freely between galaxies in the cluster. Thought to form by the stripping of satellite galaxies as they fall into the cluster, characterising the ICL is key to understanding the assembly mechanisms occurring inside galaxy clusters. Despite its importance, little is known about this light as it is very difficult to observe due to its low surface brightness. The availability of deep surveys have expanded our knowledge of the properties, and therefore the origin, of the ICL. However, larger samples are needed to understand the evolution of this component with time and the efficiency of the different evolutionary processes inside galaxy clusters.

In this talk, I will present the latest advances in our understanding of the ICL and the possibility to explore the dark matter distribution in galaxy clusters by using this diffuse light. I will also talk about the technical challenges of low surface brightness imaging, the lessons learned from past deep imaging that will help us to better prepare for upcoming surveys and unveil the ICL.

Speaker: Kathryn Neugent, University of Toronto

Abstract: The detection of gravitational waves (GW) has ushered in a new era of astrophysics. While mergers of compact objects lead to these events, our understanding of the massive star progenitors is lacking. My PhD research focused on characterizing one subset of these progenitors: the evolved massive red supergiants (RSG) in binary systems. I'm now extending this research to explore both the direct GW progenitor systems of RSGs currently interacting with their companions (both stellar and compact objects), as well as the failed GW progenitor systems that end either in stellar mergers or RSGs with distant stellar companions. In this talk, I'll cover what we've learned so far about RSGs in binary systems and what the future holds in terms of identifying interacting systems and potential merger products. By comparing observations and population statistics of these various systems with predictions from current population synthesis models, soon we will know both how these GWs occur and how many we expect to detect in the future.

Biography: Dr. Kathryn Neugent studies massive stars across the HR Diagram from hot OB and Wolf-Rayet stars, to cool yellow and red supergiants primarily in the Local Group galaxies M31, M33, and the Magellanic Clouds. Kathryn obtained her undergraduate degree in Computer Science and Astronomy from Wellesley College before pursuing a career in cyber security for several years. However, she missed astronomy and decided to come back to the field and recently graduated with her PhD in Astronomy from the University of Washington. She is currently a Dunlap Fellow at the University of Toronto and will be starting as a Pappalardo Fellow at MIT this summer. For more information, see her website: https://kathrynneugent.com.