At the SPICE-Workshop on Bad Metal Behavior in Mott Systems (June 29-July 2 2015) in Mainz, Germany, I was invited speaker. I gave a talk about glassy dynamics in theta-RbZn, the organic material that upon fast-cooling can avoid the charge ordering transition and gets into a disorderfree electron glass phase. At the hand of four characteristics of a glass – slow dynamics, a soft gap, short-range correlations and a rugged energy landscape – I discuss the results of our model of hoppings electrons with long-range Coulomb repulsion.
From June 1 to June 5, 2015, the KITP hosted the conference ‘Closing the entanglement gap: Quantum information, quantum matter, and quantum fields,’ where I presented a poster on my recent (unpublished) work on the entanglement spectrum of a coplanar antiferromagnet. The entanglement entropy attains a logarithmic term from the tower of states, proportional to the number of Goldstone modes, the entanglement spectrum represents the full SO(3) symmetry of the tower of states.
At 7 May 2015 I gave a public outreach talk for Café KITP at Club Soho in Santa Barbara, for a general audience, with the title ‘Quasiparticles – The Dreams That Stuff is Made Of‘. The idea is that I showed how in solid materials all new kind of ‘fundamental’ particles can arise known as ‘quasiparticles’. In fact, we can engineer any kind of particle – even particles that do not exist in the theory of fundamental particles (the Standard Model) like magnetic monopoles and ‘anyons’. The existence of quasiparticles underlies all modern electronic technology and will give rise no new technologies such as quantum computers.
At the APS March Meeting 2015 I presented recent work on the Efros-Shklovskii Gap without disorder.
Abstract: Certain models of frustrated electron systems have been shown to self-generate glassy behavior, in the absence of disorder. Possible candidate materials contain quarter-filled triangular lattices with long-range Coulomb interactions, as found in the θ-family of organic BEDT-TTF crystals. In disordered insulators with localized electronic states, the so-called Coulomb glass, the single particle excitation spectrum displays the well-known Efros-Shklovskii gap. The same excitation spectrum is investigated in a class of models that display self-generated electronic glassiness, showing pseudogap formation related to the Efros-Shklovskii Coulomb gap. Our study suggests universal characteristics of all electron glasses, regardless of disorder.
This are the Powerpoint slides of a talk that I gave at the Washington University in St. Louis, and later at the Lorentz Institute, Leiden University, The Netherlands. The abstract was:
Glass, like ordinary window glass, is known for thousands of years, yet it lacks a universal physical description. We do know that unlike normal phases of matter – think of gas, liquid, solids – a glass cannot reach its state of lowest free energy. This is due to a loss of ergodicity, and can also happen in a many-electron system. Usually electron glasses are considered in the presence of disorder, yet last year it was shown that a group of clean organic crystals (known as theta-(BEDT-TTF)_2MM’-(SCN)_4 with M=Tl,Rb,Cs and M’=Co,Zn) also display glassy behavior. We will discuss those results, including the Arrhenius behavior of the relaxation time. After that, we will explain the self-generated glassy physics in terms of frustration arising from the triangular lattice and the Coulomb interaction between the electrons. Mean field theory, exact diagonalization and Monte Carlo simulations provide a quantitative picture of this particular clean electron glass.
Download the powerpoint file (6MB) here: Triangular Glasses
At the DRSTP Trends in Theory conference, where I was also in the organizing committee, I presented a poster on frustration and cooperation in correlated exciton condensates. There I was runner-up in the Best Poster Presentation award. This poster was also used at the “Universal Themes of Bose-Einstein Condensation“-workshop at the Lorentz center.
As a visitor of the MagLab in the group of Vlad Dobrosavjlevic, I had the opportunity to present my work at a Seminar at the MagLab in Tallahassee, FL. Here you can find already a nice hint of the conclusion:
The full presentation (PDF, 12 MB) can be downloaded here.
In January 2013 I managed to be at two places at the same time: in FOM Veldhoven and at the Winter School in the National High Magnetic Field Laboratory in Tallahassee, FL, USA. Okay, to be honest: I was physically in Florida, whilst Robert-Jan and Kai made sure my poster was presented in Veldhoven. Thanks guys!
The poster, entitled “Exciton condensation in strongly correlated electron bilayers“, can de downloaded here (PDF, 4.4 MB).
At the EXCON 2012 conference in Groningen and at the `Innovations in Strongly Correlated Electron Systems’ Summer School and Workshop at the ICTP (Trieste, Italy) I presented this poster about the most recent developments in the exciton business. You can download the poster here (PDF, 1.6 MB).
As a quasi-member of the Interfaces and Correlated Electron systems (ICE) group from Hans Hilgenkamp I joined the ICE2UK-tour. Together with Marcel Hoek, who is also on the VICI project, I gave a talk in Bristol – the hometown of Nevill F. Mott! We couldn’t resist, the talk is called ‘Mott insulator bilayers’, and can be downloaded here (PDF, 10 MB).