Spring 2017

Quantum Behaviors of Graphene Plasmons

Speaker(s): 
Changgan Zeng
Dates: 
Thursday, March 23, 2017 -
4:30pm to 5:30pm

Discovering exotic quantum effects of plasmons and their coupling with other quasiparticles in solids may help to understand such collective excitations at the fundamental level, and further offer quantum-mechanical solution to design future quantum devices with optimized functionalities. In this talk, I will present our recent progress on the quantum behaviors of pasmons in graphene. In particular, I will show the control of plasmon excitation and propagation by tuning the quantum transmission at Heaviside potential steps. Moreover, I will also demonstrate that when the...

Quantum Phases and Phase Transitions in Two-Dimensional Highly Correlated Metals at Oxide Interfaces

Speaker(s): 
Ramesh Budhani
Dates: 
Thursday, April 20, 2017 -
4:00pm to 5:00pm

The two-dimensional diffusive metal stabilized at the interface of SrTiO3 and the Mott Insulator perovskite LaTiO3[1-2] has challenged many notions related to the formation and electronic behavior of the two-dimensional electron gas (2DEG) at the well studies LaAlO3-SrTiO3 interface. Here we discuss specifically the stability of the superconducting phase[3] at LaTiO3 – SrTiO3 interface, the nature of the superconductor – normal metal quantum phase transition (T=0 limit) driven by magnetic field, significance of the field vis-à-vis the Chandrasekhar - Clogston limit for...

My Adventures in Nano-Land

Speaker(s): 
Matthew Johnson
Dates: 
Thursday, March 30, 2017 -
4:30pm to 5:30pm

In this talk, I will describe my background and my approach to the fabrication of nanostructures through three different interdisciplinary projects while highlighting potential applications of the nanosystems we have developed and exciting recent developments in nano-characterization. The first project uses conventional nanoprocessing to fabricate interband cascade lasers. These efficient mid-IR lasers have potential chemical sensing applications and devices of this type have been the preferred mid-IR laser for extra-terrestrial use as methane and water sensors on Mars....

Structure-Activity Relations in Heterogeneous Catalysis – A View from Computational Chemistry

Speaker(s): 
Phillipe Sautet
Dates: 
Friday, March 17, 2017 -
9:30am to 10:30am

The understanding of the catalytic properties of nanoparticle catalysts and the design of optimal composition and structures demands fast methods for the calculation of adsorption energies. By exploring the adsorption of O and OR (R=OH, OOH, OCH3) adsorbates on a large range of surface sites with 9 transition metals, we propose new structure sensitive scaling relations between the adsorption energy of two adsorbates that are valid for all metals and for all surface sites.1 This opens the way for a new class of activity volcano plots where the descriptor is not an energy...

Magnetic Nanostructures: A Playground for Fundamental Physics

Speaker(s): 
Ran Cheng
Dates: 
Thursday, March 2, 2017 -
4:30pm to 5:30pm

Nature becomes amazingly different from what we perceive with our eyes when zoomed in to the nanometer scale, where atomic spins interact and form diverse magnetic configurations. Besides holding great technological promise, magnetic nanostructures have also enabled a vibrant playground for fundamental physics—a thriving field known as spintronics. In this talk, I will introduce selected recent progress in spintronics that has reshaped our understanding of transport phenomena occurring at the microscopic scale. Special attention will be paid to antiferromagnetic...

Kagome Spin Liquids and Nuclear Relaxation Rates in Herbertsmithites

Speaker(s): 
Rajiv Singh
Dates: 
Tuesday, February 28, 2017 -
4:00pm to 5:00pm

The Kagome Lattice Heisenberg Model is one of the simplest realistic spin models with a quantum spin-liquid ground state. We discuss the current status of our understanding of this well-studied model. The precise nature of the spin-liquid state and the existence of a spin-gap in the model still remain in dispute. We also discuss experimental studies of Herbertsmithite material Kagome-antiferromagnet ZnCu_3(OH)_6Cl_2. We focus on NMR measurements by Imai and collaborators, who have presented strong evidence for a spin-gap in the excitation spectra. Through a Numerical...

Control of Light-Matter Interaction in 2D Atomic Crystals

Speaker(s): 
Vinod Menon
Dates: 
Thursday, April 6, 2017 -
4:30pm to 5:00pm

Two-dimensional (2D) atomic crystals have emerged as a very attractive class of optoelectronic material due to the unprecedented strength in its interaction with light. In this talk I will discuss approaches to enhance the strength of this interaction even further using microcavities, and metamaterials. Specifically I will discuss enhancement of spontaneous emission [1], formation of strongly coupled exciton-photon quasiparticles (microcavity polaritons) [2], valley polarized polaritons and enhancement of nonlinear optical response from 2D transition metal...

Using Ultrafast Laser Pulses and Computational Modeling to Understand Nonproportionality in Spectroscopic Gamma-Ray Detectors

Speaker(s): 
Richard Williams
Dates: 
Thursday, March 23, 2017 -
12:00pm to 1:30pm

Under gamma-ray or charged-particle excitation, scintillation light yield is a complicated function of carrier diffusion and cooling in the track along with kinetic rate terms depending on local excitation density. Up to 1021 electron-hole pairs/cm3 are produced in an initial track radius of about 3 nm. Extracting the fundamental rate constants directly from such conditions would require solving the diffusion and cooling problems in complex track structures first. Laser interband photon density response and time-resolved pump-probe studies are surrogate experiments that...

Nanotechnology: Small Things Matter

Speaker(s): 
Chad Mirkin
Dates: 
Thursday, February 2, 2017 -
4:30pm to 6:00pm

Nanotechnology is an interdisciplinary field focused on studying and manipulating ultraminiaturized structures, ones with at least one dimension 10,000 times smaller than the diameter of a human hair. This field has the potential to transform almost every aspect of our lives for the better – from enabling our cell phones and computers to run faster to generating our power more efficiently to making our tennis racquets and golf clubs lighter and more durable to making our medicines and drugs more efficacious. How can such small materials lead to such big advances in...

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