Argonne National Laboratory

Colloquium Series

The Center for Nanoscale Materials holds a regular biweekly colloquium on alternate Wednesdays at 11:00 a.m. in Bldg. 440, Room A105/106. The goal of the series is to provide a forum for topical multidisciplinary talks in areas of interest to the CNM and also to offer a mechanism for fostering interactions with potential facility users. Refreshments will be served at 3:30.

Committee Members:

  • Xiao-Min Lin (Chair)
  • Pierre Darancet
  • Ralu Divan
  • Xuedan Ma
  • Elena Rozhkova
  • Jianguo Wen
Date TItle

February 22, 2017
11:00 am
Bldg. 440, A105-106

"Dimensionally Control of Complex Transition Metal Compounds", Turan Birol, University of Minnesota.  Host:  Kendra Letchworth-Weaver

 

The fact that the dimensionality of transition metal compounds’ crystal structures have a strong effect on their macroscopic properties is well known, but the microscopic mechanism by which this happens is not always obvious. First principles methods, such as Density Functional Theory or Dynamical Mean Field Theory, are capable of providing insight that can help uncover the mechanisms of dimensional reduction. In the first half of this talk, I will discuss the microscopic mechanism behind the emergence of novel polar phases in SrTiO3 Ruddlesden-Popper compounds, present results from first principles calculations, and clarify how the interfacial rumpling, only recently observed experimentally in these systems, is responsible of the dimensional reduction. The second half of the talk will be on low connectivity fluoroiridate compounds which, according to our Dynamical Mean Field Theory calculations, host a J=1/2 Mott insulator state because of the interesting interplay between the crystal structure, electronic correlations, and spin-orbit coupling.

March 8, 2017
11:00 am
Bldg. 440, A105-106

"Harnessing and Avoiding Loss in Optical Metamaterials", Jason Valentine, Vanderbilt University.  Host:  Gary Wiederrecht

 

Optical metamaterials are man-made materials in which structuring is used to control the effective optical properties. Metamaterials have traditionally been made from metals and absorption loss has long been one of the primary impediments to their adoption in practical applications. Over the past several years researchers have come to realize that loss can not only be harnessed for certain applications but also completely avoided when transparency of the material is critical. In this talk, I will start by discussing how absorption loss in plasmonic materials can be utilized in energy conversion devices by harvesting hot electrons within the metal. In this case, the use of metamaterials provides the freedom to engineer the optical absorption while also optimizing the geometry of the metal for efficient capture of the hot electrons. In the second half of the talk I will discuss all-dielectric metasurfaces in which metal, and the accompanying absorption, is completely avoided. As with their plasmonic counterparts, manipulation of the unit cell structure of all-dielectric metasurfaces offers a means to engineer a wide variety of optical properties. This freedom, combined with the reduction in absorption loss, could lead to ultra-thin optical elements and assemblies. Along these lines, I will discuss several implementations of all-dielectric metasurfaces with functionalities that include polarization control, wavefront tailoring, near-unity reflection, and sharp Fano resonances.

March 22, 2017
11:00 am
Bldg. 440, A105-106

"Transport and Spectroscopy of Illuminated Molecular Junctions", Abraham Nitzan, University of Pennsylvania.  Host:  Tal Heilpern

 

The interaction of light with molecular conduction junction is attracting growing interest as a challenging experimental and theoretical problem on one hand, and because of its potential application as a characterization and control tool on the other. From both its scientific aspect and technological potential it stands at the interface of two important fields: molecular electronics and molecular plasmonics. I shall review the present state of the art of this field and our work on optical response, Raman scattering, temperature measurements, light generation and photovoltaics in such systems. 

April 5, 2017
11:00 am
Bldg. 440, A105-106

Aditya Mohite, Los Alamos National Laboratory.  Host:  Xuedan Ma

April 19, 2017
11:00 am
Bldg. 440, A105-106

 

May 3, 2017
11:00 am
Bldg. 440, A105-106

Sudipta Seal, University of Central Florida:  Host:  Elena Shevchenko

May 17, 2017
11:00 am
Bldg. 440, A105-106

Payel Das, IBM Thomas J. Watson Research Center.  Host:  Robert Winarski or Supratik

May 31, 2017
11:00 am
Bldg. 440, A105-106

Matteo Cargnello, Stanford University, Department of Chemical Engineering.  Host:  Elena Rozhkova

June 14, 2017
11:00 am
Bldg. 440, A105-106

 

June 28, 2017
11:00 am
Bldg. 440, A105-106

 

July 12, 2017
11:00 am
Bldg. 440, A105-106

 

July 26, 2017
11:00 am
Bldg. 440, A105-106

 

August 9, 2017
11:00 am
Bldg. 440, A105-106

 

August 23, 2017
11:00 am
Bldg. 440, A105-106

 

August 30, 2017

11:00 am

Bldg. 440, A105-106

Polina Anikeeva, Massachusetts Institute of Technology (MIT).  Host:  Elena Shevchenko

September 6, 2017
11:00 am
Bldg. 440, A105-106

 

September 20, 2017
11:00 am
Bldg. 440, A105-106