News & Outreach


Screening of Coulomb interactions in Holography.

31 December, 2018

The high-temperature superconductors are so-called strange metals that have a number of properties that are very hard to understand. The holographic principle known from string theory has recently had some succeses in explaining some of these properties. However, this principle applies in first instance only to neutral systems, whereas the strange metals consist of electrons that have an electric charge. In this paper we show how to generalize the holographic principle to be able to consider also many-body systems of charged electrons with (long-range) Coulomb interactions. Moreover, we show how also the layered structure of the high-temperature superconductors, where the electrons move primarily on two-dimensional copper-oxygen planes, can be taken into account as well.

Read more in the pre-print..

[1] Enea Mauri, Henk Stoof, Screening of Coulomb interactions in Holography, arXiv:1811.11795.

Workshop & School on Strange Metals

3-5 January, 2018

2018 started with an exciting workshop featuring several internationally renowned speakers. With a 50-50 mix between experiment and theory, we experienced for the first time how challenging it can be to understand each others language. We are grateful for the effort made by all speakers to get this to work!
The workshop was preceded by a one day school with introductory lectures.
Henk Stoof introduces concepts from AdS/CFT.
Milan Allen gives an intro to STM/STS experiment.

The intertwined order of high Tc superconductors and a black hole with fancy hair.

7 November, 2017

The electron systems formed in copper oxides responsible for superconductivity at a high temperature are famously enigmatic. Part of this mystery are the concerted (“intertwined”) exotic electronic ordering patterns competing with the superconductivity as observed in experiment. According to the so-called holographic duality as discovered in string theory such many body quantum systems may be in a precise mathematical relation to the gravitational physics of black holes in a space with an extra dimension. Different from the astrophysical variety, these black holes are allowed to have “hair” — properties such as an atmosphere. Resting on the most general traits of the gravitational theory imposed by symmetry and locality the black hole as of relevance to the electron systems turns out to develop a remarkably textured “hair cut” [1]. Translated to the electrons, this becomes intriguingly similar to the salient features of the intertwined order. Specifically, according to holography the high temperature metallic state is a densely many-body entangled affair. When it becomes unstable at low temperature, parity breaks spontaneously driving charge density modulations accompanied by spontaneous current patterns. The news is that the black hole hair also describes a superconducting state of a kind that appears to be observed in the copper oxides while it is very hard to explain by conventional condensed matter theory. This is the “pair density wave”, a spatially modulated superconductor with a vanishing average and a periodicity locked to the charge density modulations.

Read more in the press release or the article.

[1] Rong-Gen Cai, Li Li, Yong-Qiang Wang and Jan Zaanen, Intertwined Order and Holography: The Case of Parity Breaking Pair Density Waves, Phys. Rev. Lett. 119, 181601 (2017).