At this years edition of the annual Dutch Physics@FOM conference in Veldhoven I will present a poster entitled “*Exciton condensation in strongly correlated electron bilayers*“. Actually, for the first time the poster will actually be about exciton condensation, the initial goal of my PhD research.

In the picture here you see an excerpt from the poster, explaining the exciton t-J model Hamiltonian. The poster itself can be downloaded here (pdf, 1.3 MB).

## Presentation: Frustrated interlayer excitons in antiferromagnets

On 9 September 2011 I was presenting my work on interlayer excitons (see this preprint) at the University of Utrecht in the so-called ‘BEC group meeting’ (that is: the groups of Henk Stoof, Rembert Duine and Cristiane de Morais Smith combined).

Title:Frustrated interlayer excitons in antiferromagnets (click to download the presentation in PDF, 3.6 MB)

## Poster at NSPM 2011, Erice (and OECS12)

In Erice (a beautiful place in Sicily, Italy) both a summer school and a workshop was held about “Quantum Phenomena in Graphene, other Low-Dimensional Materials, and Optical Lattices“. Needless to say I was there for the “other low-dimensional materials”, with lectures on bilayer exciton condensation (by Allan MacDonald) and oxide heterostructures. At the workshop part I presented a poster on my latest work on excitons in bilayer quantum antiferromagnets, which you of course can download here.

**Poster title:** Dynamical frustration of interlayer excitons in bilayer quantum antiferromagnets (PDF, 397 kB)

In addition, I discovered that Shou-Cheng Zhang used the picture Jeroen Huijben made for me in his presentation of topological insulators. Zhang’s presentation (amongst others) can be downloaded here.

**Update:** I presented this very same poster at the international conference on Optics of Excitons in Confined Systems (OECS12) in Paris, 12-16 September 2011.

## Physics@FOM Veldhoven 2010 / Lorentz Workshop April 2011 Poster

At the Physics@FOM Veldhoven 2010 (January 19, 2010) conference I presented a poster with the title “How a Neutral and Massless Superfluid can still exhibit Flux Quantization” (pdf, 2.8 MB).

*Image: In concentric bilayers a supercurrent of excitons will exhibit a quantization of the flux in between the two cylinders. The magnetic field lines are shown in red. (Figure made by Jeroen Huijben.)*

**Update, March 12, 2010**: Recently we found that the results, as presented in Veldhoven, were not completely correct. Flux quantization does appear in exciton double layers, however, the trapped flux must be a multiple of $latex \frac{h}{e} \chi_m$ where $latex \chi_m$ is the diamagnetic susceptibility of the exciton double layer.

**Update, April 4, 2011**: At the Lorentz workshop ‘100th Anniversary of Superconductivity’ I presented a corrected version of the poster. The results have by now been peer-reviewed and published in PRB. On this website I replaced the incorrect old version with the new correct version!

## Presentation at the DRSTP Spring School 2011

This year at the Dutch Research School for Theoretical Physics AIO/OIO School for Statistical Physics and Theory of Condensed Matter (aka the DRSTP SPTCM School 2011) I gave some introduction to the idea of linear spin-wave theory and how it can be applied to interlayer excitons. More information on the school itself can be found here, the presentation itself can be downloaded below.

Title: Excitons and spins in strongly correlated systems (pdf, 741 kB)

## Physics@FOM Veldhoven poster on exciton motion

This years contribution to the annual FOM meeting in Veldhoven is a poster entitled “Exciton motion in strongly correlated heterostructures” (PDF, 700 kB). It was a combined poster with my collaborators from Twente (Marcel Hoek, Francesco Coneri and Hans Hilgenkamp), who were responsible for the experimental part; and with Kai Wu and Jan Zaanen, my theoretical colleagues in Leiden.

## Presentation at Stripe Club, january 2011

Today Kai Wu and I gave a presentation at Jan Zaanen’s group meeting called the “Stripe Club”. Our presentation was named “The motion of a single exciton in a bilayer quantum antiferromagnet” (PDF, 1.9 MB). In summary: we developed a spin wave theory for the bilayer Heisenberg model in order to describe the motion of an exciton through such a bilayer, which we solved using the self-consistent Born approximation. Recently, we obtained numerical results for the exciton spectral function. It appears to be that the Ising-type ladder spectrum reappears even though quantum fluctuations are taken into account, as you can see in the following ‘teaser’ result for alpha=0.2.

## Poster MESA+ meeting 2010

My colleagues at the Twente University and me together presented a poster at the MESA+ Institute for Nanotechnology Meeting 2010 held in Enschede at 14 September. The title of our poster was “Bose-Einstein condensation of excitons in oxide heterostructures” and can be downloaded (3.7 MB).

## Presentation at Casimir Spring School 2010

Last week at the Casimir Spring School 2010 I was invited to give a talk on my work on ‘Flux Quantization in Double Layer Exciton Superfluids’. With this talk I was awarded the prize for best oral presentation! 🙂 You can download the presentation here in Powerpoint-format. Note that this talk is intended for general physics PhD-audiences. A more theoretical talk can be found here.

**Title**: Flux Quantization in Double Layer Exciton Superfluids (pptx, 7.5 MB)

**Abstract**: We predict an unconventional magnetic flux quantization effect to occur in double layer exciton superfluids and we discuss designs for a device to measure this universal electromagnetic signature of the exciton superfluid. This would provide an unambiguous test for the macroscopic phase coherence associated with an exciton Bose-Einstein Condensate.

## Presentation at DRSTP School 2010

At the Dutch Research School for Theoretical Physics AIO/OIO School for Statistical Physics and Theory of Condensed Matter (aka the DRSTP SPTCM School 2010) I gave the following presentation on flux quantization in the exciton double layers. Note that this talk is aimed at a theoretical PhD-students level.

**Title**: Magnetic Flux Quantization in Double Layer Exciton Superfluids (pptx, 7.9 MB)