Condensed Matter Seminars

Competition of Topological and Nematic Phases in the Two-dimensional Electron Gas

Speaker: 
Gábor Csáthy, Department of Physics and Astronomy and the Birck Nanotechnology Center, Purdue University
Event Date and Time: 
Thu, 2016-12-01 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
Joshua Folk
Intended Audience: 
Graduate

The two-dimensional electron gas is a prototypical strongly correlated system which, over the years, has contributed to the development of novel concepts in condensed matter physics such as fractional charge, composite fermions, edge states, Pfaffian correlations, non-Abelian statistics, and topological order. The two-dimensional electron gas hosted in GaAs/AlGaAs heterostructures has a particularly rich set of ground states. Well-known examples are the fractional quantum Hall states and various exotic electronic solids.

Josephson Currents Induced by the Witten Effect

Speaker: 
Jeroen van den Brink, Institute for Theoretical Solid State Physics, IFW Dresden, Germany
Event Date and Time: 
Thu, 2016-11-24 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
Mona Berciu
Intended Audience: 
Graduate

We reveal the existence of a new type of topological Josephson effect involving type II superconductors and three-dimensional topological insulators as tunnel junctions. We predict that vortex lines induce a variant of the Witten effect that is the consequence of the axion electromagnetic response of the topological insulator: at the interface of the junction each flux quantum attains a fractional electrical charge of e/4.

Superfluid density and microwave conductivity of FeSe superconductor

Speaker: 
David Broun, Department of Physics, Simon Fraser University
Event Date and Time: 
Thu, 2016-11-17 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
Doug Bonn
Intended Audience: 
Graduate

FeSe is an iron-based superconductor of immense current interest due to the large enhancements of Tc that occur when it is pressurized or grown as a single layer on an insulating substrate.  In collaboration with the UBC superconductivity group, we have carried out precision measurements of the superconducting electrodynamics of bulk material, at frequencies of 202 and 658 MHz and at temperatures down to 0.1 K.

Macroscopic character of composite high temperature superconducting wires and enhancement of superconductivity by magnetic field

Speaker: 
Boris Spivak, University of Washington
Event Date and Time: 
Thu, 2016-11-10 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
Philip Stamp

d-wave symmetry of the superconducting order in the cuprate high temperature superconductors is a well established fact, and one which identifies them as unconventional. However, in macroscopic contexts including many potential applications (i.e. superconducting wires) the material is a composite of randomly oriented superconducting grains in a metallic matrix, in which Josephson coupling between grains mediates the onset of long-range phase coherence.

Driven Dirac Materials

Speaker: 
Alexander Balatsky (Nordita and Los Alamos National Laboratory)
Event Date and Time: 
Fri, 2016-11-04 12:00 - 13:00
Location: 
Hennings 318
Local Contact: 
Marcel Franz
Intended Audience: 
Graduate

Recent pump-probe experiments demonstrate the possibility that Dirac materials (DMs) may be driven into transient excited states describable by the state with two separate inverted occupancies, one for

Magnetism meets topology: Quantum anomalous Hall effect and Chiral spin liquids

Speaker: 
Arun Paramekanti, University of Toronto
Event Date and Time: 
Thu, 2016-10-20 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
Ian Affleck

First, I will discuss recent developments in the field of oxide heterostructures, and present our proposal to realize half-metallic Chern bands and a high Tc quantized anomalous Hall effect in mixed 3d/5d oxides. A key component of this proposal involves an orbital analogue of the Rashba effect which may have broader implications in orbitally degenerate oxides.

Cooper like pairing induced by electron ionic polarizability

Speaker: 
Yizhak Yacoby, Hebrew University of Jerusalem
Event Date and Time: 
Thu, 2016-09-22 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
George Sawatzky

Using the fact that the electron ionic polarizability response time is practically instantaneous we show that a charge carrier induces large attractive potential to a second carrier in small pockets in the two particle position space. Taking into account the inter-carrier repulsion and the kinetic energy needed in order to confine the carriers to the attractive potential pockets we find that the pairing energy is of the order of the energies seen in high Tc superconductors.

Design and manipulation of functional molecular nanosystems

Speaker: 
Johannes Barth, Department of Physics, Technical University of Munich
Event Date and Time: 
Wed, 2016-08-10 14:00 - 15:00
Location: 
AMPEL 311
Local Contact: 
Sarah Burke
Intended Audience: 
Graduate

Towards realizing topological superconductivity in quantum wires

Speaker: 
Vincent Mourik, University of New South Wales
Event Date and Time: 
Thu, 2016-06-23 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
Dmitry Pikulin
Intended Audience: 
Graduate

The engineering of topological superconductors and the observation and control of their non-abelian quasiparticles is a dominant effort in condensed matter physics, both out of fundamental interest and for their potential application in topological quantum computing.

Cross-interface electron-phonon interactions in FeSe Films on oxide substrates

Speaker: 
Steve Johnston, University of Tennessee
Event Date and Time: 
Thu, 2016-06-02 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
Mona Berciu
Intended Audience: 
Graduate

A flurry of scientific activities has been generated by the discovery of a significantly enhanced superconductivity in ultra thin films of FeSe grown on oxide substrates such as SrTiO3 .

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