Seminar

Energy (and spin) transport in the thermal phase of the disordered Heisenberg chain

Speaker(s): 
Vipin Varma
Dates: 
Thursday, April 28, 2016 - 4:30pm to 5:30pm

We study energy transport at high temperature in the thermal phase of the disordered Heisenberg chain [1]. Starting from nonequilibrium initial conditions that are either well within linear response or well outside of it, we show that a phenomenological hydrodynamic description captures the mechanism for equilibration. In particular, an energy diffusion constant is identified which vanishes in the thermal phase even before the localisation transition: the thermal phase is separated into diffusive and subdiffusive regimes. If time permits, similar results will be shown to hold for the...

Directly Imaging the Super States of Nature

Speaker(s): 
Mohammad Hamidian
Dates: 
Thursday, May 5, 2016 - 4:00pm to 5:00pm

A superconductor is a homogeneous quantum condensate of Cooper pairs, each formed by binding two electrons into a zero-spin, zero-momentum eigenstate.  In 1964 Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) [1,2] proposed an alternative ground state wavefunction of Cooper pairs thus arriving at a new super state of electronic matter. The resulting pairs carry momentum Q requiring the superfluid density to modulate with wavevector Q.  Remarkably, the same...

Simulating grain boundaries at the atomic scale: more complicated than you think

Speaker(s): 
Stephen Foiles
Dates: 
Friday, April 29, 2016 - 11:30am to 12:30pm

The grain microstructure is well-known to have a profound influence on the properties of materials so there is great interest in the properties of grain boundaries. Atomic-scale simulations have been used to study grain boundary properties for over three decades, but there are still many unanswered questions. This reflects the complexity associated with the five geometric degrees of freedom, temperature, and alloy additions and impurities. In this talk,...

Silicon CMOS Platform for Quantum Information Processing

Speaker(s): 
Silvano De Franceschi
Dates: 
Wednesday, April 13, 2016 - 11:00am to 12:00pm

I will present the first realizations of double quantum dots in dual-gate nanowire transistors. We have observed the spin-blockade effect (useful for spin readout), electrically-driven hole-spin resonance, and, very recently, we obtained the first proof of concept of a CMOS hole-spin qubit.

Emergent Phenomena at a Mott Insulator/Band Insulator Interface

Speaker(s): 
Yuri Suzuki
Dates: 
Friday, April 22, 2016 - 3:30pm to 4:30pm

Advances in solid-state devices have been enabled by the introduction of new materials platforms and their subsequent improvements in carrier concentration, mobility and breakdown voltages. To this end, the exploration of interfaces, where a novel functionality or phenomenon is generated at the interface of two materials that is not present in either of the bulk forms of the constituent materials, is promising. With recent developments in complex oxide thin film deposition techniques, novel ground states at perovskite oxide interfaces have been studied...

Nanostructure-Controlled Heterogeneous Catalysts with Superior Catalytic Properties

Speaker(s): 
Wenyu Huang
Dates: 
Thursday, April 7, 2016 - 4:00pm to 5:30pm

Dr. Huang received a B.S. in Chemistry from Nanjing University, China in 2000. After receiving an M.S. in 2002 also from Nanjing University, he started his Ph.D. research with Professor Mostafa A. El-Sayed at Georgia Institute of Technology and received his Ph.D. in 2007. Dr. Huang then began postdoctoral research with Professor Gabor A. Somorjai at University of California,...

The Manhattan Project: Beyond the Physics

Speaker(s): 
Cameron Reed
Dates: 
Monday, March 28, 2016 - 4:30pm to 6:00pm

The Manhattan Project was the United States Army’s effort to develop the first generation of nuclear weapons, which were used against Japan in August, 1945 and helped bring World War II to an end. The Project involved the coordination of hundreds of thousands of people to solve challenging problems in physics, engineering, large-scale industrial organization, production, security, personnel training, political and military strategy, and ethics that were unique for their time and whose legacies are still with us today. The methods by which various scientific and...

Simulating an Exploding Fission-Bomb Core With a Desktop Computer

Speaker(s): 
Cameron Reed
Dates: 
Monday, March 28, 2016 - 2:30pm to 4:00pm

This colloquium will describe a program developed for a desktop computer which carries out a time-dependent simulation of the core of an exploding nuclear weapon. The logic of the program is understandable to any student familiar with kinematics and vectors; the necessary nuclear concepts will be introduced as needed. The simulation models a core comprising a mixture of two isotopes: A fissile one (such as uranium-235) and an inert one (such as uranium-238) that captures neutrons and removes them from circulation. The user sets the enrichment percentage and...

Ultrafast dynamics of ferroelectrics and transition metal dichalcogenides

Speaker(s): 
Haidan Wen
Dates: 
Thursday, March 24, 2016 - 3:30pm to 4:30pm

The quest of new states of matter in the time domain and the need for ultrafast control of material properties have been fueled by the recent advance of large-scale ultrafast x-ray facilities. These new experimental capabilities enable direct probe of structural dynamics with unprecedented spatial and temporal resolution, shedding light on the fundamental material processes and guiding the design of ultrafast devices. In the first example, I will show that the ultrafast optical and terahertz excitations offer new pathways of controlling lattice structure of...

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