| Tuesday, January 29, 2019 |
| Emergent nonequilibrium dynamics of complex solids | |
| Matteo Mitrano, University of Illinois | |
| Event Type: CQP Faculty Search | |
| Time: 9:30 AM - 10:30 AM | |
| Location: 726 Broadway, 940, CCPP Seminar | |
| Abstract: Ultrafast optical excitation, especially when resonant to specific lattice modes, has recently emerged as a powerful means to control complex solids and their phase transitions. One of the most ambitious applications of these optical methods is the possibility to manipulate the lattice and the electronic interactions to bring about nonequilibrium superconductivity at temperatures far above the thermodynamic critical temperature Tc. In this talk, I will discuss how midinfrared optical excitation of the BCS-like superconductor K3C60 led to an emergent nonequilibrium superconducting-like phase above its equilibrium Tc. This light-induced state is suppressed by external pressure, as expected for a conventional BCS superconductor, but its microscopic origin is still unclear. In order to further our understanding of these phenomena, it is necessary to go beyond ultrafast optics and instead probe electronic excitations at finite momentum. I will report the recent observation of collective, finite-momentum dynamics of a charge order condensate in the cuprate La2-xBaxCuO4 using next-generation time-resolved X-ray scattering methods. Finally, I will discuss how ultrafast electron and X-ray scattering will enable the observation of novel nonlinear effects in the charge, spin and lattice response of complex solids. | |
| Modjaz Group Mtg | |
| Event Type: Modjaz Group Mtg | |
| Time: 11:00 AM - 12:30 PM | |
| Location: 726 Broadway, 901, Sm Conf | |
| New Cosmological Probes of the Lightest and Heaviest Dark Matter | |
| Ely Kovetz, JHU | |
| Event Type: Astro Seminar | |
| Time: 2:00 PM - 3:15 PM | |
| Location: 726 Broadway, 940, CCPP Seminar | |
| Abstract: The dark matter landscape, ranging from fuzzy dark matter to primordial black holes, spans more than 90 orders of magnitude in mass. We will discuss how new and upcoming cosmological observables can probe models that lie on the extreme ends of this spectrum. We will first present an updated picture of the scenario of primordial black holes as dark matter. Placing an emphasis on the stellar-mass window motivated by the most recent LIGO detections, we will introduce constraints from astrophysical transients such as gravitational waves from merging black holes, fast radio bursts and more. We will then turn to the 21cm global signal at cosmic dawn, and advocate for its unique sensitivity to interactions between the dark and visible sectors. In particular, we will discuss the suggested dark matter explanation for the recently claimed detection of an anomalous 21cm absorption profile by the EDGES experiment, showing that the viable parameter space is highly fine-tuned. Finally, we will demonstrate how a robust detection of the 21cm global signal at cosmic dawn can be used to place the strongest bounds to date on ultra-light hidden-photon dark matter. | |