Wednesday, February 25 — Josh Kennedy
Affiliation: AFRL
Time:
4:00 PM
Location:
C215 ESC
or Live Online
Polarization- and Spin-Dependent Optoelectronics in Intrinsically Chiral Semiconductors
Hybrid organic-inorganic perovskites (HOIPs) comprise a family of semiconductors with many attractive properties for optoelectronics including high photoexcited carrier densities, moderate carrier mobility, shallow trap defects, and scalable solution processing. The incorporation of chiral organic molecules in these structures can give rise to chiral distortions in the inorganic sublattice that produce polarization- and spin-dependent phenomena such as circular dichroism, circular birefringence, spin polarized photoexcitation, and spin-dependent transport. These chiral HOIPs (CHOIPs) enable unprecedented control over the degree of chiral distortion via tailoring their composition and processing parameters. Our team has investigated a wide variety of CHOIPs in an effort to discover the relationship between the structure of the organic cation and the chiroptic properties of interest. I will discuss how multiple meta-stable crystal phases in these systems complicate efforts to optimize CHOIP thin films for chiral optoelectronics, and I will highlight the unique opportunities for materials engineering that we ar exploiting for future applications such as polarization-sensitive photodetectors and on-chip circularly polarized emitters.
Biographical Sketch:
Dr. W. Joshua Kennedy received his B.Sc. in Physics from the College of Charleston and his Ph.D. in Physics from the University of Utah. Before joining the Air Force Research Laboratory in 2014, he worked at the University of Texas at Dallas and at NASA’s Johnson Space Center. He is now a Senior Research Physicist at AFRL, where he leads the Agile Electronic Materials and Processes Research Team in the Materials and Manufacturing Directorate at Wright-Patterson Air Force Base, Ohio.
Wednesday, March 4 — William Black
Affiliation: BYU Physics and Astronomy
Time:
4:00 PM
Location:
C215 ESC
or Live Online
Wednesday, March 11 — Eric Gibbs
Affiliation: Case Western Reserve
Time:
4:00 PM
Location:
C215 ESC
or Live Online
Wednesday, March 18 — David Cullen
Affiliation: ORNL
Time:
4:00 PM
Location:
C215 ESC
or Live Online
Electron Microscopy
Wednesday, March 25 — Joe Jensen
Affiliation: UVU
Time:
4:00 PM
Location:
C215 ESC
or Live Online
Addressing the Hubble Tension with JWST
The sharp conflict between the current expansion rate of the universe (the Hubble constant, or H0) measured using the local extragalactic distance ladder and the value of H0 derived from the cosmic microwave background has the potential to reveal the presence of additional physics beyond the LCDM standard model of cosmology, so reducing and eliminating sources of systematic uncertainty in the local distance scale is of paramount importance. I will describe our efforts to calibrate the surface brightness fluctuation technique using the tip of the red giant branch to enable measurements of H0 at distances beyond 200 Mpc with JWST while minimizing systematic uncertainties. The results of our TRGB+SBF project are completely independent of the Cepheid+supernova distance ladder and form one of the key components of a new “Distance Network” that has now been used to accurately assess the covariances between various distance measurements and techniques. The Distance Network results reaffirm the reality of the Hubble tension at the 6-sigma level and further reduce the systematic uncertainties on H0, providing evidence that additional physics beyond cold dark matter and traditional dark energy may exist.
Biographical Sketch:
Dr. Joseph Jensen is an astronomy professor in the Physics Department at Utah Valley University. He currently uses the Hubble and James Webb Space Telescopes to study the size and expansion rate of the universe by measuring distances to galaxies hundreds of millions of light years away. He received his Ph.D. in astronomy from the University of Hawaii at Manoa. Dr. Jensen worked at the Gemini Observatory for 12 years during the construction and commissioning of the twin telescopes. Dr. Jensen has been at UVU for 16 years and works with undergraduate students on optical and infrared imaging projects in cosmology.
Wednesday, April 1 — Raman Sundrum
Affiliation: University of Maryland
Time:
4:00 PM
Location:
C215 ESC
or Live Online
Wednesday, April 8 — Daniel Lerch
Affiliation: Siemens Corp
Time:
4:00 PM
Location:
C215 ESC
or Live Online
Wednesday, April 15 — James Orgill
Affiliation:
Time:
4:00 PM
Location:
C215 ESC
Wednesday, September 9 — Ming Yi
Affiliation:
Time:
4:00 PM
Location:
C215 ESC
Wednesday, September 16 — Kent Gee
Affiliation: BYU Physics and Astronomy
Time:
4:00 PM
Location:
C215 ESC
We welcome anyone who wish to attend, and typically serve refreshments ten minutes before the colloquium begins. Speakers generally keep their presentation accessible to undergraduate physics students.