Seminar

Phase-field Modeling of Polar States in Ferroelectric Heterostructures

Speaker(s): 
Long-Qing Chen
Dates: 
Thursday, March 28, 2019 - 4:00pm

This presentation will discuss the applications of the phase-field method to understanding and discovering new mesoscale polar states that might emerge from nanoscale ferroelectric heterostructures subject to different mechanical and electric boundary conditions. As an example, the determination of thermodynamic conditions and geometric length scales leading to the formation of ordered polar vortex lattice as well as mixed states of regular domains and vortices in ferroelectric superlattices of PbTiO 3 /SrTiO 3 using phase-field simulations and analytical theory will be presented. Switching of these vortex lattice states might produce other transient polar states such as polar skyrmions. It is shown that the stability of these vortex lattices involves an intimate competition between long-range electrostatic, long-range elastic,
and short-range polarization gradient-related interactions leading to both an upper- and a lower- bound to the length scale at which these states can be observed. We further predicted the periodicity phase diagrams that show excellent agreements with experimental observations by collaborators.

Phase-Change Photonics for All-Optical Memory and Computation

Speaker(s): 
Dr. Nathan Youngblood
Dates: 
Wednesday, February 20, 2019 - 12:00pm

Phase-change materials have been used commercially as an optical storage medium in the last few decades owing to their high optical contrast and long-term stability, but only recently has a fully integrated photonic device been demonstrated. This approach not only enables all-optical memory on-chip, but also allows multilevel data storage with improved SNR, low switching energy, and high speed operation. In this talk, an overview of integrated, non-volatile photonic memory based on the phase-change material Ge2Sb2Te5 (GST) will be presented, together with...

Universal Themes of Bose-Einstein Condensation conference (UBEC 2019)

Speaker(s): 
Multiple Speakers
Dates: 
Monday, April 1, 2019 - 9:00am

The UBEC conference series addresses broad themes of BEC that cross through all types of condensates, including cold atoms, helium and hydrogen, superconductors, quasiparticle condensation, photons and lasing, and condensation in nuclear physics, astrophysics and cosmology.

The conference will begin with an evening reception Sunday, March 31, and end Friday, April 5, at 3:00 pm. Talks will begin Monday, April 1, promptly at 9:00 am. There will be a poster session on Tuesday, April 2, and conference excursions on the afternoon of Thursday, April 4. The conference banquet will be ...

Quantum Nanophotonics: Engineering Atom-Photon Interactions on a Chip

Speaker(s): 
Dr. Shuo Sun
Dates: 
Monday, February 18, 2019 - 12:00pm

The ability to engineer controllable atom-photon interactions is at the heart of quantum optics and quantum information processing. In this talk, I will introduce a nanophotonic platform for engineering strong atom-photon interactions on a semiconductor chip. I will first discuss an experimental demonstration of a spin-photon quantum transistor [1], a fundamental building block for quantum repeaters and quantum networks. The device allows a single spin trapped inside a semiconductor quantum dot to switch a single photon, and vice versa, a single photon to flip the spin. I will discuss how...

Creating and measuring the elusive Majorana fermions

Speaker(s): 
Dr. Vidya Madhavan
Dates: 
Monday, April 29, 2019 - 4:30pm

Dirac discovered that every fundamental particle must also have a distinct anti-particle which has the opposite charge. When particles and anti-particles meet, they annihilate each other releasing energy. In 1937, Ettore Majorana predicted the existence of a special class of particles where the particle and the anti-particle are identical. However, with the possible exception of neutrinos, so far there are no known fundamental particles that belong to this class. Recently, the possible realization of these exotic Majorana fermions as quasiparticle excitations in in solids has created much...

mK to km: How Millikelvin Physics is Reused to Explore the Earth Kilometers Below the Surface

Speaker(s): 
Dr. Robert Kleinberg
Dates: 
Monday, January 28, 2019 - 4:00pm

Robert L. Kleinberg is an Adjunct Senior Research Scholar at the Center on Global Energy Policy of the Columbia University School of International and Public Affairs.  From 1980 to 2018 he was employed by Schlumberger, attaining the rank of Schlumberger Fellow, one of about a dozen who hold this rank in a workforce of 100,000. He has served on or advised numerous government and academic committees on energy policy, and is a coauthor with Harvard faculty of a textbook on energy technology, in preparation. Dr. Kleinberg was educated at the University of California, Berkeley (B.S. Chemistry, 1971) and the University of California, San Diego (Ph.D. Physics, 1978). From 1978 to 1980 he was a post-doctoral fellow at the Exxon Corporate Research Laboratory in Linden, NJ. His work at Schlumberger focused on geophysical measurements and the characterization and delineation of unconventional fossil fuel resources. His current interests include energy technology and economics. Dr. Kleinberg has authored more than 100 academic and professional papers, holds 38 U.S. patents, and is the inventor of several geophysical instruments that have been commercialized on a worldwide basis. He is the recipient of the 2018-2019 American Physical Society Distinguished Lectureship Award on the Applications of Physics, and is a member of the National Academy of Engineering. He is also a Non-Resident Senior Fellow at the Boston University Institute for Sustainable Energy.

Electrically conductive metal-organic frameworks: insights from theory

Speaker(s): 
Christopher Hendon
Dates: 
Tuesday, February 12, 2019 - 4:00pm

Porous electrical conductors are a desirable yet evasive class of materials that would play a key role in the development of novel electrical energy storage devices. Their high surface area and electrical conductivity enable the uptake of electrolyte into their pores, forming the basis for a supercapacitive device. Metal-organic frameworks are an emerging subset of porous materials with fleeting reports of electrical conductivity suitably high for super capacitor implementation. This talk discusses our efforts to understand what gives rise to conductivity in metal-organic frameworks, and...

Understanding Molecular and Hybrid Crystals from First Principles

Speaker(s): 
Leeor Kronik
Dates: 
Thursday, January 17, 2019 - 2:30pm

Molecular crystals are crystalline solids composed of molecules bound together by relatively weak intermolecular interactions, typically consisting of van der Waals interactions and/or hydrogen bonds. Hybrid crystals combine molecular units and covalent/ionic networks.

Both classes of crystals play an important role in many areas of science and engineering, ranging from biology and medicine to mechanics and electronics. Therefore, much effort has been dedicated to understanding their structure and properties.

Predicting the behavior of such materials from first

...

Nonlinear Dynamics and Quantum Computers

Speaker(s): 
Dr. Susan Coppersmith
Dates: 
Friday, November 30, 2018 - 12:00pm

John David Crawford was an expert in dynamical systems and bifurcation theory, which is the study of systems that are subject to strong driving. This talk will discuss why this area of research is important for quantum computation. In particular, it will be shown how concepts from nonlinear dynamics proved to be critical in the development and improvement of qubits, the fundamental building blocks of quantum computers, using quantum dots in silicon/silicon-germanium heterostructures.

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