Physics Department Current Events
11:00 a.m., Marshak Science Building Room 418N
Dr. Alexey Chernikov
Postdoctoral Research Scientist, Department of Physics, Columbia University
"Excitons in atomically thin two-dimensional materials"
Since the discovery of graphene, a single sheet of carbon atoms, research focused on two-dimensional (2D) materials evolved rapidly due the availability of atomically thin, thermally stable, high-quality crystals with intriguing physical properties. The 2D materials naturally inherit major traits associated with systems of reduced dimensionality: strongly enhanced Coulomb interactions, efficient light-matter coupling, and sensitivity to the environment. In particular, the considerable strength of the Coulomb forces between the charge carriers introduces a rich variety of many-body phenomena. In the class of 2D semiconductors this leads to the emergence of strongly bound electron-hole quasi-particles, such as excitons, trions, and biexcitons, with unusually high binding energies and efficient light absorption.
In this talk, I will present a study of the excitonic properties of 2D semiconductors, as exemplified in recent works on atomically thin transition metal dichalcogenides. The observation of exciton binding energies on the order of 0.5 eV and the marked deviation of the exciton Rydberg series from the hydrogenic model will be discussed. The results reflect both strong carrier confinement and the distinctive nature of dielectric screening in atomically thin materials. I will further describe how non-equilibrium conditions such as strong photo-excitation can profoundly alter the many-body interactions in these systems.
Bio: Alexey Chernikov is currently working as a postdoctoral researcher at Columbia University (New York, USA) in the group of Tony F. Heinz, studying excitonic phenomena in low-dimensional nanomaterials, organic crystals, and hybrid perovskite structures. He obtained his PhD degree in 2012 at the University of Marburg (Germany) with the research focused on ultra-fast spectroscopy of nanomaterials, studies of many-body phenomena and development of high-power vertical-emitting semiconductor lasers. He was awarded with the Feodor-Lynen Fellowship from the Alexander von Humboldt Foundation in 2013.
Wednesday, April 22, 2015
4:00 p.m., Marshak Science Building Room 418N
Professor Institute for Advanced Studies, Princeton
"The earliest moments in the history of our Universe"
We currently have a very successful cosmological model that allow us to understand how the structure we see on large scales in our Universe formed and evolved. The seeds for this structure were produced before the hot phase of the Big Bang and thus their study could shed light on the earliest moments in the history of our Universe. I will summarize the recent observational results and discuss what we can expect to learn in the future.
12:30 p.m., Marshak Science Building Room 418N
Principal, Maxwell Consulting
"Banking on Physics"
Would the world be better if physicists ran the banks? Certainly it’s worth a try! The Credit Crisis beginning in 2007 is merely the latest historical event to demonstrate the inherent fragility of national and global banking systems. Applying the perspective of “a physicist seeking truth,” we diagnose core problems of banking and propose simple and drastic reforms.
This lecture discusses “physicists in finance” at a general level portraying both successes and failures. Ironically, what many perceive as physicists’ greatest strength – building sophisticated models – is actually our failure. To give substance, context, and examples, we describe the investigation into the death of Lehman Brothers and the larger topic of the structural flaws of banking and how to fix them.
Joe Pimbley earned a Ph.D. in theoretical physics from the Rensselaer Polytechnic Institute concurrently with his full-time role as a semiconductor device physicist at the GE Corporate Research & Development Laboratory. He then migrated to a position of assistant professor of mathematical sciences with contributions, publications, and patents in the fields of numerical methods, signal processing, and nuclear, chemical, and electrical engineering.
After 13 years of physics, math, and engineering, Joe pivoted to the financial world. After years of exposure to almost all of the challenges of the capital markets, Joe became a lead investigator for the Lehman bankruptcy court to determine causes of history’s largest bankruptcy. His work yielded important findings for funding, leverage, collateral, liquidity, and valuation challenges that led to the Lehman failure and the resulting Crisis. With his co-author, Joe published “the physicist’s guide to fixing banking:” Banking on Failure – Fixing the Fiasco of Junk Banks, Government Bailouts, and Fiat Money.
4:00-5:30 p.m., North Academic Center Ballroom (1st floor, west side beyond bookstore)
Distinguished Professor, Physics Department, The City College of New York
“Advocating for Women in Science: Advocating for the Human Rights of all Scientists”
Myriam Sarachik is Distinguished Professor of Physics at The City College of New York. On Thursday, April 23, she speaks of her past experiences and her life-long advocacy for women in science and the human rights of scientists everywhere in the final talk of City College’s inaugural “Presidential Conversations: Activism, Scholarship, and Engagement” series.
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