Hosted by: Dmitri Zakharov

The demand for developing new energy technologies continues to push characterization tools, to tackle the high level of complexity found in active materials for energy conversion processes. The frontiers of basic energy research require new generations of instrumentation to understand complex materials and chemical systems, energy systems in realistic working environments, and systems that are dynamic, far from equilibrium, and extremely heterogeneous. Advanced imaging and spectroscopy in the transmission electron microscope offers unprecedented opportunities to interrogate structure and charge transfer functionalities in energy materials based on thermochemical, photochemical and electrochemical processes. To understand functionality, it is important to characterize these systems under real world conditions i.e. in situ and operando. The enormous advances in electron optics has pushed spatial resolutions below 1 Å for imaging and 1 – 2 Å for spectroscopy. Electron energy-loss spectroscopy has also undergone a revolution with energy resolution Bio: Peter A. Crozier is a professor of materials and is chair of the Materials Graduate Program at Arizona State University. He develops and applies advanced transmission electron microscopy techniques to problems related to energy and the environment with special emphasis on electroceramics and catalytic materials. He has published extensively on in situ electron microscopy and is a recognized international leader in developing and applying the technique of aberration corrected transmission electron microscopy to problems in catalytic materials and oxide electrolytes. He also pioneered the application monochromated electron energy-loss spectroscopy to determine the optical and vibrational properties of materials. He is a member of the American Ceramics Society, Microscopy Society of America, Materials Research Society, the North American Catalysis Society and is a Fellow of the Microscopy Society of America. He is currently President of the Microscopy Society of America. Please click the link below to join the webinar: https://bnl.zoomgov.com/j/1601921599?pwd=N3lKeG9UTElIUGxjcGVRYnhBaHcwQT09 Passcode: 938341 ***********************************************Or iPhone one-tap : US: +16692545252,,1601921599#,,,,,,0#,,938341# or +16468287666,,1601921599#,,,,,,0#,,938341# Or Telephone: Dial(for higher quality, dial a number based on your current location): US: +1 669 254 5252 or +1 646 828 7666 Webinar ID: 160 192 1599 Passcode: 938341 International numbers available: https://bnl.zoomgov.com/u/acnmbonoCa Or an H.323/SIP room system: H.323: 161.199.138.10 (US West) or 161.199.136.10 (US East) Meeting ID: 160 192 1599 Passcode: 938341 SIP: 1601921599@sip.zoomgov.com Passcode: 938341

Hosted by: Yong Zhao

Abstract: Exotic hadrons, which are composed of more than three valence quarks, can provide new insights into the internal structure and dynamics of hadrons, thus improving our knowledge of the non-perturbative regime of QCD. Since 2003, various candidates for exotic states have been observed, to which the LHCb experiment has made major contributions. This seminar discusses the studies on exotic hadrons at LHCb. The most recent observation of structure in the $J/\psi$-pair invariant mass spectrum and study of resonant structure in $B^+ \to D^+ D^- K^+$ decays are presented.

Hosted by: Mircea Cotlet

A novel nanosensor enabling ultra-sensitive detection of antibody-ligand and receptor-ligand interactions is presented. The nanosensor detects optical and electrical molecular signatures to characterize both low-affinity (µM) and high-affinity (nM) interactions, as well as separate specific from non-specific interactions. This novel technology's name originates from the fact it uses a Self-Induced Back-Action (SIBA) mechanism for optical trapping to enable SIBA-Actuated Nanopore Electrophoresis (SANE) sensing. Our high-affinity model consisted of T-cell receptor-like antibodies engineered to target peptide-presenting Major Histocompatibility Complex ligands, representing a model of target ligands presented on the surface of cancer cells. Our low-affinity model of consisted of a natural-killer cell receptor targeting peptide-presenting receptors reconstituted from cancer cells, as a simplified model of interactions that occur during cancer immunotherapy. We were able to detect ligand-receptor complex binding at concentrations up to 1000 times lower than the free solution equilibrium binding constant (KD) for both low-affinity and high-affinity interactions, potentially offering very significant savings in expensive protein reagents. Additionally, SANE sensor measurements enabled estimation of the fast dissociation rate (koff) for the low-affinity specific ligand-receptor system, previously shown to be challenging to quantify with commercial technologies. The koff value of targeted peptide-presenting ligands is known to correlate with the subsequent activation of immune cells in vivo, suggesting the potential utility of the SANE senor as a screening tool in cancer immunotherapy. At the end of this talk I will also be presenting emerging new applications of the SANE sensing technology for the characterization of adeno-associated virus preparations for gene therapy and the label-free readout of their genetic content as a future low-cost approach to single virus DNA sequencing. https://bnl.zoomgov.com/j/1617324438?pwd=aEtGa0hGK1dvSGJrNkRrZlhoZ3BIUT09 Meeting ID: 161 732 4438 Passcode: 241672

Hosted by: Deyu Lu

Twisting van der Waals heterostructures to induce correlated many body states provides a novel tuning mechanism in solid state physics. In this work, we theoretically investigate the fate of the surface Dirac cone of a three-dimensional topological insulator subject to a superlattice potential. Using a combination of diagrammatic perturbation theory, lattice model simulations, and ab initio calculations we elucidate the unique aspects of twisting a single Dirac cone with an induced moire potential and the role of the bulk topology on the reconstructed surface band structure. We report a dramatic renormalization of the surface Dirac cone velocity as well as demonstrate a topological obstruction to the formation of isolated minibands. Due to the topological nature of the bulk, surface band gaps cannot open; instead additional satellite Dirac cones emerge, which can be highly anisotropic. We discuss the implications of our findings for future experiments. Ref: https://arxiv.org/abs/2010.09726 Host: Deyu Lu Webinar https://bnl.zoomgov.com/j/1617324438?pwd=aEtGa0hGK1dvSGJrNkRrZlhoZ3BIUT09 Meeting ID: 161 732 4438 Passcode: 241672

Hosted by: Mircea Cotlet

Van der Waals (vdW) layered materials open up new opportunities in modern electronics as they can be readily isolated into atomically thin monolayers, resulting in two-dimensional (2D) confinement of carriers. vdW heterostructures formed by stacking these 2D materials as building blocks have a wide range of optoelectronic properties and unprecedent physical phenomena. By using cathodoluminescence in electron microscope, I will show here how the structural properties of interfaces of vdW heterostructures play roles in the optical emission and charge carrier transport. In particular, I will discuss the effect of (1) twisted interface, (2) heterointerface, and (3) deformed (curved) interface on the luminescence. I demonstrate (1) tunable optical emission controlled by twist angle, (2) nanoscale optical/structure characterization of a monolayer transition metal dichalcogenides, and (3) enhanced luminescence by optical cavity effect of vdW heterostructures.