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.
Last week I put my work on exciton dynamics in strongly correlated bilayers onto the arXiv!
Title: The dynamical frustration of interlayer excitons delocalizing in bilayer quantum antiferromagnets
Abstract: Using the self-consistent Born approximation we study the delocalization of interlayer excitons in the bilayer Heisenberg quantum antiferromagnet (see figure above). Under realistic conditions we find that the coupling between the exciton motion and the spin system is strongly enhanced as compared to the case of a single carrier, to a degree that it mimics the confinement physics of carriers in Ising spin systems. We predict that the ‘ladder spectrum’ associated with this confinement physics should be visible in the c-axis exciton spectra of insulating bilayer cuprates such as YBa2Cu3O6. Our discovery indicates that finite density systems of such excitons should show very rich physical behavior.
Reference: Louk Rademaker, Kai Wu, Hans Hilgenkamp and Jan Zaanen, arXiv:1106.5347
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)
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.
Today my supervisor Hans Hilgenkamp got appointed as professor in Experimental Physics at Leiden University. In the corresponding press release (in Dutch) I’m mentioned in the third paragraph, as I’m his only PhD-student in Leiden. The press release describes briefly the main focus of our research: electron correlations at interfaces.
Today I start officially as PhD-student in Theoretical Physics under the supervision of Hans Hilgenkamp, Jan Zaanen and Jeroen van den Brink. The latter two are professors in theoretical physics at the Lorentz Institute, Leiden University. Professor Hans Hilgenkamp, from Twente University, is the main supervisor since he got a Vici-grant for our research.
The Vici is granted to Hilgenkamps’ proposal which is titled “Opposites attract; Electron-hole dances in coupled p- and n-type Mott-conductors“. The goal of the research is to realize and investigate new states of matter by coupling p-type and n-type Mott materials.
Continue reading “Vici project “Opposites attract” starts”