A memory of heat

Vo2 memristor

We are witnessing a truly remarkable moment: the birth of an artificial intelligence. Large language models, machine learning and deep fakes are all running on distributed computing networks that use a tremendous amount of energy. For example, the training of chat-GPT used up approximately 1 GWh of energy. The projections are that at the current … Read more

The surprising effect of nothing


In 2015, a team in Strasbourg made an amazing (and controversial) claim: The electrical conductivity of a material can be dramatically enhanced by embedding it in a tailored photonic environment. Remarkably, light was not involved.  The enhancement was due to the coupling of electron-hole pairs to the vacuum field, i.e., to nothing.  The team recently … Read more

Measuring transient violations of the 2nd law

Normal 0 false false false NL JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:”Table Normal”; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:””; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:”Calibri”,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:”Times New Roman”; mso-bidi-theme-font:minor-bidi; mso-ansi-language:NL;} The 2nd law of thermodynamics has been revised many times over the past 2 … Read more

The mysterious normal state of TiSe2


The layered material TiSe2 is famous for several reasons, one of which is the discovery of a new state of matter “excitonium” [1]. This state involves the spontaneous formation and Bose-Einstein condensation of excitons, resulting in an elemental electronic crystal in which excitons play the role of atoms.   The formation of excitonium has been … Read more

Quantifying excitonic light scattering in 2D nanophotonic metasurfaces


Supervisors: Thomas Bauer and Jorik van de Groep Monolayer 2D semiconductors exhibit uniquely strong light-matter interactions in the visible spectral range due to quantum mechanical exciton resonances. When patterned on the nanoscale, light can be confined into these atomically thin layers of material and pick up a scattering phase and amplitude that is dictated by … Read more

Excitonic light-matter interactions in heterostructure 2D solar cells (joint project)


Supervisors: Tom Hoekstra, Peter Schall, and Jorik van de Groep Since the isolation of graphene in 2004, more than two thousand layered 2D materials have been identified. These materials can be exfoliated from bulk down to atomically thin monolayers, which exhibit unique optical and electronic properties, including stable excitons at room temperature. By employing a … Read more

Superlubric particles for friction and wear reduction

Graphene Layers for friction reduction (artist's impression)

Supervisors: Abhishek Gupta and Peter Schall Friction between moving parts and the associated wear are responsible for about 25% of the world’s energy consumption. Superlubricity is a new mechanism of ultralow friction between solid surfaces, achieved with 2D materials such as graphene when sliding along incommensurate lattice directions (see image below). In this project, we … Read more

Solarfoil: Nanocrystal spectral converters for green economy

Solar light spectral shaping by nanocrystals

Supervisors: Ina Flaucher and Peter Schall  Despite many years of photosynthesis research, the photosynthetic efficiency remains low. One reason is that plants use only limited spectral regions for photosynthesis; the solar spectrum, however is much broader, containing much more energy. We develop highly efficient nanocrystal layers to “shape” the solar spectrum into an optimum spectrum … Read more

Active Photonic Metasurfaces

Triggered light operations with an active metasurface

Includes a 3-4 months internship at: Osaka University, Japan (Prof. Dr. Fujiwara) Supervisors: N. de Gaay Fortman, F. Koenderink, P. Schall Metasurfaces are 2D arrangements of nanostructures that resonantly scatter and jointly can act as analogue signal processing components:  upon reflection or transmission of light, they can encode a complex optical function, programmed as an … Read more

AI-assisted nanophotonic inverse design of optical sensors

Screenshot 2023-03-21 at 10.50.23

Nanomaterials have optical properties that strongly depend on their geometry and are therefore are often used as tunable signal transducers in optical sensors. For example, palladium nanoparticles are capable of detecting H2 gas by absorbing hydrogen within its metallic lattice, leading to a modified electronic structure and optical appearance. Recently, we have shown that periodic … Read more