Presentation: Integrals of Motion with Displacement Transformations

15At the KITP conference ‘KITP Conference: Aspects and applications of many-body localization‘ from 16 to 20 November, here in Santa Barbara, my collaborator Miguel Ortuño gave a presentation about the work we have been doing together on MBL.

You can watch the talk on the website of the KITP:

The slides of the presentation can be downloaded here, and the paper that explains our work in more detail is currently on the arXiv.


Presentation: Glassy dynamics in geometrically frustrated Coulomb liquids

mainzAt 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.

You can download the presentation here (pdf, 10 MB).

The talk has been posted on Youtube: click here to watch it!

Poster: The Tower of States and the Entanglement Spectrum in a Coplanar Antiferromagnet

Poster KITP conferenceFrom 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entanglement gap: Quantum information, quantum matter, and quantum fields,’ where I presented a poster on my recent (unpublished) work on the entanglement spectrum of a coplanar antiferromagnet.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.

You can download the poster here (pdf, 1.3 MB).

Presentation, Cafe KITP: Quasiparticles


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.

Download the presentation here (pptx, 10 MB)

Presentation: Efros-Shklovskii Gap without disorder

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.

Download the presentation here (pdf, 5.4 MB).

Presentation: Self-generated electron glasses in frustrated organic crystals

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