As a kid, were you ever curious to know what lice looked like from really close by? Or even a mosquito? To do this you would definitely need to use a microscope, in order to observe all the complex structures of these insects.
Invented …
Clarivate Web of Science has released its annual list of Highly Cited Researchers, including three ICREA Group Leaders at ICFO:
* Dr. Javier Garcia de Abajo- Cross Field Category
* Dr. Frank Koppens- Cross Field Category
* Dr. Macie…
The General Assembly of Laserlab-Europe AISBL, the international not-for-profit association representing 45 leading laser research infrastructures in 22 European countries, elects ICREA Professor at ICFO Dr Jens Biegert as new Executive Director and ap…
Until very recently, the idea of watching how molecules break, or transform, during chemical reactions was unfathomable. In 2016, researchers from ICFO developed mid-IR-driven laser induced electron diffraction (LIED) with kinematic coincidence detecti…
Precise detection of magnetic fields is important for applications that range from magnetic brain imaging, to detection of sunken ships, to exploration of the solar system. For many of these applications, the most sensitive magnetic-field measuring ins…
Since Albert Einstein provided a theoretical foundation for Robert Brown’s observation of the erratic or unpredictable movement of microscopic particles suspended within pollen grains, significant new findings that deviate quite a bit from the laws of …
We congratulate Dr Niels Caspar Herman Hesp who defended his thesis today in ICFO’s auditorium with online participations due to social distancing to contain the Coronavirus pandemic.
Dr Hesp obtained his MSc degree in Physics of Molecules and Materials from Radboud University in Netherlands. He joined the Quantum Nano-Optoelectronics research group led by ICREA Prof Dr Frank Koppens as a master student to work on hot carrier dynamics in high quality graphene. Afterwards, for his doctoral thesis, he narrowed down the topic to focus specifically on Twisted Bilayer graphene and study its possible potential and capabilities through different innovative experimental techniques. Dr Hesp thesis entitled “Exploring Twisted Bilayer Graphene with Nano-Optics” was supervised by Prof Dr Frank Koppens.
ABSTRACT:
Nano-optics studies the behaviour of light on the nanoscale. In particular, it probes the interaction of light with objects, often of nanometre-size, and reveals fine details of the material’s optical properties. Optoelectronics is an integral part of optics and describes the interaction between light and electronics, such as the detection of light and subsequent conversion to an electrical signal. Understanding such mechanisms at the nanoscale is of importance for improving imaging and light-harvesting applications. In this Thesis, we apply near-field microscopy to study optics on the nanoscale. It probes optical properties using light interacting with the near-field electromagnetic field near the material’s surface.
Twisted bilayer graphene (TBG) is formed by stacking two layers of graphene – a one-atom-thick sheet of carbon atoms – with a small twist angle. This causes an interference pattern in the atomic lattice called a moiré pattern, which affects the electronic properties dramatically. The discovery of unconventional superconductivity in TBG in 2018 made it a thriving field of research. Adding to this, TBG revealed strongly correlating states and topological features, making it a host of tunable exotic phases that may shed light on the origins of unconventional superconductivity. These phenomena motivate us to study the optical properties of TBG on a nanoscale, which have received little attention thus far.
In the first part of this Thesis, I describe spatially oscillating patterns within selected regions of TBG that we detected using near-field microscopy. We interpret them as a manifestation of plasmons — electrons moving collectively in a wave-like pattern — driven by interband transitions. We model these areas with a reduced interlayer coupling, which enhances the strength of interband transitions and explains the observed plasmon dispersion.
After this, I discuss large-scale periodic features observed in minimally twisted bilayer graphene (?
In 1998 astronomers discovered that the expansion of the universe is accelerating. Somehow, something must have made gravity repulsive on cosmological scales. This something was called dark energy, and it amounts to about 70% of the total mass of the u…
Lasers, devices that emit light in one direction, with photons traveling at one specific frequency and all with the same phase (coherent), govern the way we communicate today. Although lasers are known to most people as little torches emitting high pur…
When two layers of graphene are placed one on top of the other, and twisted among them by a very small angle, a “moiré pattern” is formed and the physical properties of the system have proven to change dramatically. In particular, near the ‘magic’ angl…
We congratulate Dr Nils-Eric Guenther who defended his thesis today with online participations due to social distancing to contain the Coronavirus pandemic.
Dr Guenther obtained his Master in Fundamental Physics from the Ecole Normale Superieur…
Quantum-confined materials exhibit tunable optical, electrical, chemical and physical properties. Intensive research carried out since their discovery four decades ago has led to a deepened understanding of these materials, their properties and their m…