Condensed Matter Physics Seminars – 2012

Friday, 30 November 2012, 12:00 PM

Ferroelectric Heterostructure

Shivani Rajput, UWM Physics Graduate Student

Friday, 16 November 2012, 12:00 PM

Weyl Semimetals

Prof. Daniel Agterberg, UWM Physics

Friday, 4 May 2012, 12:00 PM

UWM Discovery Advances Graphene-Based Electronics

Prof. Marija Gajdardziska-Josifovska, UWM Physics

Scientists and engineers at UWM have discovered an entirely new carbon-based material that is synthesized from the “wonder kid” of the carbon family, graphene. The discovery, which the researchers are calling “graphene monoxide (GMO),” pushes carbon materials closer to ushering in next-generation electronics.

GMO exhibits characteristics that will make it easier to scale up than graphene. And, like silicon in the current generation of electronics, GMO is semiconducting, necessary for controlling the electrical current in such a strong conductor as graphene. Now, all three characteristics of electrical conductivity—conducting, insulating and semiconducting—are found in the carbon family, offering needed compatibility for use in future electronics.

This is collaborative work between four PI groups. UWM Physics Ph.D. student Eric Mattson and Marija made the initial discovery by in-situ electron diffraction. Adding IR with Carol Hirschmugl et al., DFT with Mike Weinert et al., and transport with Junhong Chen et al., we solved the structure and established semiconducting properties.

Friday, 6 April 2012, 12:00 PM

Principles and Applications of Electron-Optical Phase Shift Retrieval in a Transmission Electron Microscope (electron holography and the transport-of-intensity-equation formalism)

Dr. Marvin Schofield, Senior Scientist, UWM Physics

A moving electron acquires an additional phase shift as it passes through an electrostatic or magnetic vector potential. With conventional transmission electron microscopy techniques, this phase shift information is lost as only the intensity of the electron wave (i.e., its amplitude-squared) is recorded. Off-axis electron holography, and a lesser-known technique called the transport-of-intensity-equation (TIE) formalism, allow direct recovery of the electron-optical phase shift and, hence, may probe the electric and magnetic fields associated with materials of interest.

In this talk I will discuss the significance of the electron-optical phase shift and present the principles of electron holography and the TIE formalism in a dual perspective of theory and experiment. I will provide examples of the practical application of these techniques to materials science research.

Friday, 16 March 2012, 12:00 PM (Physics 143)

Hexagonal pnictide SrPtAs; the role of spin-orbit interaction and locally broken inversion symmetry

Dr. S. H. Sonny Rhim, Physics and Astronomy, Northwestern University

A new class of pnictide superconductor, SrPtAs, differs from other pnictides: (i) hexagonal structure, (ii) strong spin‐orbit coupling, (iii) locally broken inversion symmetry despite the presence of global inversion symmetry. In this talk, electronic structure with and without spin‐orbit coupling is presented. A tight‐binding Hamiltonian based on band structure reveals locally broken inversion symmetry associated with spin‐orbit coupling results in nontrivial consequences in superconducting properties. We further discuss the possibility of raising transition temperature.

Friday, 9 March 2012, 12:00 PM (Physics 143)

Physics of Living Things: Soft Condensed Bio-Matter

Dr.habil. Marius Schmidt, Associate Professor, UWM Physics

Physical methods such as X-ray diffraction, electron microscopy and electron diffraction, Moessbauer and EPR spectroscopy, crystallography and computational approaches, are used to shine light on structure function relationships in bio-polymers. With a number of examples I will explain how these methods can be used.