Department Colloquia

The chiral anomaly in Dirac-Weyl semimetals.*

Speaker: 
Nai Phuan Ong (Princeton University)
Event Date and Time: 
Thu, 2017-03-23 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Fei Zhou
Intended Audience: 
Graduate

To date, the anomaly has been observed most clearly in the two semimetals Na_3Bi and GdPtBi. I will discuss what Weyl Fermions are, and how they may be realized in real materials. The realization allows the chiral anomaly to be observed in a crystal. I will explain what the chiral anomaly is and remark on its historical context, starting with pion decay. Finally I will discuss several tests that buttress the conclusion.

*Supported by the Moore Foundation, ARO and NSF.

 

 

 

 

 

Iron Pnictides: A New Piece in the High Tc Superconductivity Puzzle.

Speaker: 
Adriana Moreo (ORNL/Univ. Tennessee)
Event Date and Time: 
Thu, 2017-01-19 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Mona Berciu
Intended Audience: 
Graduate

During most of the last century superconductivity was observed in some metals at the very low temperatures achieved with liquid Helium. Below a critical temperature Tc electrons overcome their Coulomb repulsion thanks to an attraction created by the distortions of the ionic lattice and form Cooper pairs that can move without resistance. The efforts to raise Tc were unsuccessful until the discovery of the high Tc superconducting cuprates in 1986.

Iron pnictides: unconventional s-wave superconductors

Speaker: 
OsKar Vafek (NHMFLab/FSU, Tallahassee)
Event Date and Time: 
Thu, 2017-01-12 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Marcel Franz
Intended Audience: 
Graduate

Superconductivity results from condensation of bound electron pairs, the so-called Cooper pairs. In the conventional Bardeen-Cooper-Schrieffer theory, the attraction between electrons originates from their interaction with the ionic lattice and the exchange of quanta of the lattice vibrations, phonons. The resulting wavefunction for the Cooper pairs carries zero angular momentum, leading to s-wave superconductivity.

Hearing the Stars: New Insights into Stellar Interiors from Asteroseismology

Speaker: 
Lars Bildsten (KITP, UCSB)
Event Date and Time: 
Thu, 2017-03-30 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Douglas Scott
Intended Audience: 
Undergraduate

Long-term and sensitive space-based photometry from the Kepler and CoRoT satellites (as well as MOST) has allowed us to finally "hear" the stars. These remarkable data have yielded accurate measurements of masses, radii and distances for more than 30,000 stars across the Milky Way.  More profoundly, these observations are revealing the interior conditions of the star, clearly differentiating those that are undergoing helium burning in their cores to those that are only burning hydrogen in a shell.

A High Resolution Movie of the Night Sky with LSST

Speaker: 
Meredith Rawls (U Washington)
Event Date and Time: 
Thu, 2017-02-16 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Douglas Scott
Intended Audience: 
Undergraduate

On a mountaintop in Chile, the Large Synoptic Survey Telescope is preparing to map the night sky. When its decade-long mission begins in 2022, the LSST will image the entire visible sky every few nights with a 3.2 gigapixel camera. In this talk, I will describe the hardware and software being built to collect, process, and archive an unprecedented volume of astronomical images.

Fast Radio Bursts: a mysterious new class of astronomical object

Speaker: 
Kiyo Masui (UBC)
Event Date and Time: 
Thu, 2017-01-05 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Douglas Scott
Intended Audience: 
Undergraduate

Fast radio bursts (FRBs) are a recently discovered and poorly understood class of astronomical transient, observed at gigahertz frequencies and with millisecond durations. The dispersion of these signals by intervening plasma indicates that the sources are extragalactic and may even be at cosmological distances. Their high rate (with thousands occurring daily) and extreme brightnesses have made them challenging to explain theoretically.

Benchmarking Progress towards Quantum Computing

Speaker: 
Joseph Emerson
Event Date and Time: 
Thu, 2016-12-01 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Fei Zhou
Intended Audience: 
Graduate

Quantum information technologies are poised to radically outperform their classical counterparts by manipulating coherent quantum systems. These technologies promise new, secure forms of communication, sensors with dramatically enhanced sensitivity, and exponential gains in computational capabilities.

Topological insulators: from spin-orbit coupling to supersymmetry-on-a-chip

Speaker: 
Joseph Maciejko (University of Alberta)
Event Date and Time: 
Thu, 2016-11-17 16:00 - 17:00
Location: 
Henning 201
Local Contact: 
Fei Zhou
Intended Audience: 
Graduate

Topological insulators are an unusual class of insulators whose surfaces can carry electric currents while their bulk cannot. This surface conduction proceeds with little or no dissipation of heat, which makes topological insulators promising candidate materials for low-power electronics. In this talk I will give an overview of the field of topological insulators, and argue that recent developments in this field may lead to the observation of exotic phenomena predicted in elementary particle physics such as axions and supersymmetry.

 

101 years of General Relativity: from Einstein in 1915 to Relativistic Cosmology in the 21st century.

Speaker: 
Pedro Ferreira (Oxford)
Event Date and Time: 
Thu, 2017-01-26 16:00 - 17:00
Location: 
Hennings 201
Local Contact: 
Douglas Scott
Intended Audience: 
Undergraduate

The faulty reasoning used by Poynting in determining energy fluxes in electrical conductors

Speaker: 
Albert Curzon (SFU) & Frank Curzon (UBC)
Event Date and Time: 
Thu, 2016-10-27 16:00 - 17:00
Location: 
Hennings 201
Intended Audience: 
Undergraduate

We "point out" some possibly serious errors which can arise from Poynting's treatment of energy fluxes - especially for time independent current flows in electrical conductors. The basic error made by Poynting is that he assumed, essentially that if two vectors, A and B have the same divergence then A = B. We show how this reasoning can be extended to hydrodynamics, and bow it can be used to explain some other quite unexpected results in soccer! We will also outline some of the difficulties we have experienced in trying to publish our results.

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