Events at Physics |
Events on Thursday, March 15th, 2018
- R. G. Herb Condensed Matter Seminar
- Correlated Nanoelectronics
- Time: 10:00 am
- Place: 5310 Chamerlin Hall
- Speaker: Jeremy Levy, University of Pittsburgh
- Abstract: The study of strongly correlated electronic systems and the development of quantum transport in nanoelectronic devices have followed distinct, mostly non-overlapping paths. Electronic correlations of complex materials lead to emergent properties such as superconductivity, magnetism, and Mott insulator phases. Nanoelectronics generally starts with far simpler materials (e.g., carbon-based or semiconductors) and derives functionality from doping and spatial confinement to two or fewer spatial dimensions. In the last decade, these two fields have begun to overlap. The development of new growth techniques for complex oxides have enabled new families of heterostructures which can be electrostatically gated between insulating, ferromagnetic, conducting and superconducting phases. In my own research, we use a scanning probe to “write” and “erase” conducting nanostructures at the LaAlO3/SrTiO3 interface. The process is similar to that of an Etch-a-Sketch toy, but with a precision of two nanometers. A wide variety of nanoscale devices have already been demonstrated, including nanowires, nanoscale photodetectors, THz emitters and detectors, tunnel junctions, diodes, field-effect transistors, single-electron transistors, superconducting nanostructures and ballistic electron waveguides. These building blocks may form the basis for novel technologies, including a platform for complex-oxide-based quantum computation and quantum simulation.
- Host: Eriksson
- Theory Seminar (High Energy/Cosmology)
- De Sitter from D3-branes?
- Time: 3:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Ander Retolaza, DESY Theory Group
- Abstract: If de Sitter vacua exist in string theory compacti cations is an unanswered question. All attempts to realize such vacua are based on 4D e effective field theory descriptions. The standard procedure to construct them first deals with moduli stabilization, generically leading to anti de Sitter space, and then adds a localized source which increases the vacuum energy while leaving the stabilization untouched, typically an anti-D3-brane on a warped throat. These 4D ideas conflict with higher dimensional results telling that
in warped compacti cations one needs to include some object that violates the strong energy condition to obtain 4D de Sitter.
In this talk I will provide a 10D description of a popular 4D construction to obtain de Sitter and show that the 4D eff ective field theory misses a crucial point when trying to uplift the vacuum energy above zero. Then, I will apply this knowledge to other models in the market. - Host: Vernon Barger
- Astronomy Colloquium
- Planet Formation in the Era of ALMA
- Time: 3:30 pm - 5:00 pm
- Place: 4421 Sterling Hall, Coffee and cookies 3:30 PM, Talk begins at 3:45 PM
- Speaker: Ke Zhang, University of Michigan
- Abstract: Planetary systems are common in the universe, and our solar system is just one outcome of a vast number of possibilities. This great diversity is largely rooted and developed in their birth environments--- gas-rich protoplanetary disks around several Myr-old young stars. Therefore, studying the structures and evolutions of solids and gaseous components in these disks are necessary for our understanding of the diversity and ultimately the chance of habitability of planetary systems. I will discuss recent results from The Atacama Large Millimeter/submillimeter Array (ALMA) in characterizing protoplanetary disks, and new insight/puzzles that these results add to our understanding of planet formatting processes. In particular, I will focus on three areas: (1) the commonality of substructures in disks and their links to planet(esimal) formation, (2) new approaches to probe the planet-forming mid-plane region and locations of critical chemical transitions such as snowlines, (3) direct determination of carbon and oxygen elemental abundances in disk atmospheres and their implication for the initial atmospheric composition of extra-solar gas giants.