Colloquium Archives (before June 2017)

More recent colloquia are posted on the Physics & Astronomy Colloquia page.

Justin Kasper, Harvard-Smithsonian Center for Astrophysics

Topic: "Solar Probe Plus: Mission to the Sun"  (Video)

Abstract: The space age has revolutionized our understanding of the heliosphere, yet after more than half a century, two of the most fundamental questions in Heliophysics remain unanswered: why is the solar corona so much hotter than the photosphere? And how is the solar wind accelerated? These questions are critical to understanding the Sun and how it interacts with the solar system. In order to answer these questions NASA will send a spacecraft called Solar Probe Plus into the atmosphere of the Sun in a mission beginning in 2018. This talk will discuss the scientific motivations of a mission to the Sun, describe the spacecraft and its payload, and the broader application of this project to general questions in astrophysical and laboratory plasmas.

Gerhard Haerendel, Max Planck Institute for Extraterrestrial Physics

Topic: "Fascinating Plasma Structures - comet tails, auroral arcs, and solar prominences"  (Video)

Abstract: The lecture covers three themes from the past and present research of the lecturer. They have in common their relation to dynamic visible plasma structures. For all of them, a particular physical aspect has been selected for this presentation. Ambipolar momentum transfer dominates the interaction of the solar wind with a barium plasma cloud released from a German satellite 25 years ago. The term magnetic fractures is used to describe the process by which sheared magnetic flux tubes decouple from the line-tying ionosphere, whereby the liberated magnetic energy is being converted into kinetic energy of the auroral electrons. Downflows of cool plasma in quiescent solar prominences, as recently observed by the Solar Optical Telescope of the Japanese Hinode satellite, are interpreted as falling plasma droplets, i.e. plasmoids with detached magnetic field subject to drag forces caused by deformations of the ambient, mostly horizontal magnetic field during the downfall.

Pablo Jarillo-Herrero, MIT

Topic: "2D or not 2D, Electronic Transport in Novel Low Dimensional Materials"  (Video)

ABSTRACT: Over the past few years, the physics of low dimensional electronic systems has been revolutionized by the discovery of materials with very unusual electronic structures. Among these, graphene and topological insulators have taken center stage due to their relativistic-like electron dynamics and their potential applications in nanotechnology. In this talk I will briefly review the properties of graphene and topological insulators and discuss some of our recent quantum electronic transport experiments in these systems.

Amir Yacoby, Professor of Physics, Harvard University

Topic: "Quantum Information Processing and Metrology Using Few Electron Spins in Solids"  (Video)

ABSTRACT: Many different physical realizations of quantum bits have been studied over the past decade, including trapped ions, nuclear spins of molecules in solution, Josephson junctions and more. Among the different possible realizations, solid-state implementations have attracted considerable interest due to their promise in miniaturization and scaling, taking advantage of existing technology for fabrication. The spin qubit is one such example where a quantum bit of information is encoded in the spin state of a single electron confined to a small spatial dimension.

Stephon Alexander, Department of Physics, Haverford College

Topic: "Cosmic Inflation From Known Physics"  (Video)

ABSTRACT: The inflationary paradigm resolves most of the problems of the standard big bang model while providing a microphysical explanation of the origin of large scale structure in the universe. However, we still lack a concrete model of inflation in terms of the known fields of the standard model of particle interactions. In this colloquium, I will give a pedagogical account inflationary cosmology in the context of the standard big bang model. I will then provide evidence that inflation can be naturally realized from known physics that already exists in the Electroweak sector of our standard model. As a bonus, this model of inflation naturally is intrinsically connected to another physical mystery, the baryon asymmetry problem.

Charles Kane, Department of Physics and Astronomy, University of Pennsylvania

Topic: "Topological Insulators and Topological Band Theory"  (Video)

ABSTRACT: A topological insulator is a material that is an insulator on its interior, but has special conducting states on its surface. These surface states are unlike any other known two dimensional conductor. They are characterized by a unique Dirac type dispersion relation and are protected by a topological property of material's underlying electronic band structure. Topological insulators have attracted considerable interest as a fundamentally new electronic phase with applications from spintronics to quantum computing. In this talk we will outline the theoretical discovery of this phase and describe experiments that have observed its signatures in both two and three dimensional electronic systems. We will close by arguing that the proximity effect between an ordinary superconductor and a topological insulator leads to a novel interface state that may provide a new venue for observing a Majorana fermion and for realizing proposals for topological quantum computation.