Spring 2017

Room Temperature Magnetic Skyrmions in Engineered Multilayer Films

Speaker(s): 
Geoffrey Beach
Dates: 
Friday, April 14, 2017 - 11:30am to 12:30pm

Magnetic skyrmions [1] are particle-like twists of the magnetization taking the form of nanoscale vortices or bubbles that are topologically protected from being continuously ‘unwound’. Their small size, high stability, and ease of manipulation by electric current make them strong candidates for use as information carriers in spintronic memory and logic devices. However, magnetic skyrmions have until recently been restricted to just a few materials and observed only at low temperatures, limiting the experimental accessibility and technological application of these unique...

Cracking the Nanophysics of Oxide Interface and Heterostructures with ALL-Laser MBE

Speaker(s): 
Xiaoxing Xi
Dates: 
Tuesday, April 18, 2017 - 1:00pm to 2:00pm

Advancements in nanoscale engineering of oxide interfaces and heterostructures have led to discoveries of emergent phenomena and new artificial materials. Combining the strengths of reactive molecular-beam epitaxy and pulsed-laser deposition, we show that atomic layer-by-layer laser molecular-beam epitaxy (ALL-Laser MBE) significantly advances the state of the art in constructing oxide materials with atomic layer precision. Using Sr1+xTi1-xO3 as example, we demonstrate the effectiveness of the technique in producing oxide...

United States of America vs. Xiaoxing Xi: Why It Matters

Speaker(s): 
Xiaoxing Xi
Dates: 
Monday, April 17, 2017 - 4:30pm to 5:30pm

As Interim Chair of Temple University’s Physics Department, May 20, 2015 was a normal day for me filled with work on my class, research, promotion of colleagues, and a university task force I was chairing. I had given a public lecture for “Pint of Science,” a science festival, at an Irish pub before picking up my wife at the airport, who was returning from an overseas conference trip. My elder daughter had come home a day earlier from college for a few days. We made a plan to visit a restaurant to try their famous Korean fried chicken. All of this was suddenly and...

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...

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