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Calendar of Physics Talks Vienna
| A Holographic Fractional Topological Insulator |
| Speaker: | Carlos Hoyos (University of Washington, Seattle) |
| Abstract: | A topological insulator is a material that respects time reversal invariance
but nevertheless has an effective theta term in the electromagnetic action.
Although the system is an insulator in the bulk, there can be currents at
the interface between a normal and a topological insulator. In this case one
can also observe a quantum Hall effect applying a magnetic field to the
interface. It has been recently argued that a fractional quantum Hall
effect could also be produced if quasiparticles carrying fractional charge
exist in the material, in this sense we talk about fractional topological
insulators. This is only possible if the theory has non-trivial and usually
strong interactions. I explain what kind of effective theories could
describe fractional topological insulators and give an specific example
using a holographic construction involving D7 probe branes in a D3 near
horizon geometry. |
| Date: | Tue, 07.09.2010 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Erwin-Schrödinger-Institut, Boltzmann-HS |
| Contact: | Anton Rebhan, TU Wien |
| Effective Holographic Theories for Condensed Matter Systems |
| Speaker: | Rene Meyer (University of Crete) |
| Abstract: | The IR dynamics of effective holographic theories capturing the interplay between charge density and the leading relevant scalar operator at strong coupling are analyzed. By studying the thermodynamics, spectra and conductivities of several classes of charged dilatonic black hole solutions that include the charge density back reaction fully,
the landscape of such theories in view of condensed matter applications is characterized. Several regions of parameter space can be excluded as the extremal solutions have unacceptable singularities. The classical solutions have generically zero entropy at zero temperature, but there exists a special class with finite residual entropy. We find linear DC resistivity scaling with temperature, a hallmark feature of strange metallic behaviour. For massive carriers, it is shown that
when the scalar operator is not the dilaton, the DC resistivity scales as the heat capacity (and entropy) for planar (3d) systems, a feature observed in experiment. Regions are identified where the theory at finite density is a Mott-like insulator at T=0. We also find that at low enough temperatures the entropy due to the charge carriers is generically larger that that at zero charge density. This talk is based on the work 1005.4690. |
| Date: | Wed, 08.09.2010 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Erwin-Schrödinger-Institut, Boltzmann-HS |
| Contact: | Anton Rebhan, TU Wien |
| Holographic evolution of entanglement entropy |
| Speaker: | Esperanza Lopez (Univ. Autonoma Madrid) |
| Abstract: | We study evolution of entanglement entropy in a holographic setup. Using
an asymptotically AdS-Vaidya metric we are able to recover field theory
results obtained from quantum quenches. In particular we show that
entanglement propagates with v=1. Equilibration is achieved
only on the local level. Remarkably , the holographic derivation of this
fact requires information from behind the apparent horizon. We comment
on the possibility of deriving a thermalization time for occupation
numbers from our analysis. |
| Date: | Thu, 09.09.2010 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Erwin-Schrödinger-Institut, Boltzmann-HS |
| Contact: | Anton Rebhan, TU Wien |
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