Promotor: J. Aarts

Promotor: Prof.dr. C.W.J. Beenakker

In the Aarts lab we combine or structure materials, mostly in thin film form, in such a way that the hybrid has different and novel properties or functionalities.

Promotores: Prof.dr. D. Bouwmeester, Prof.dr. A. Fiore (TU Eindhoven)

The interest of this thesis lies in spin transport in normal metals and superconducting half-metallic junctions.

Promotores: Prof.dr. J. Zaanen & Prof.dr. K.E. Schalm

This thesis consists of two subjects, that are both a consequence of radiation pressure.

CrO2, a half-metal ferromagnet, has shown great promise for superconducting spintronics applications for nearly two decades.

In unconventional high temperature superconductors, supercurrent vortices are known to spoil the Landau levels. In this thesis the emergence of Landau levels is studied in different types of superconductors: Weyl superconductors, and the Fu-Kane heterostructure.

Promotor: C.W.J. Beenakker, Co-Promotor: A.R. Akhmerov

This thesis is devoted to an in-depth examination of the various effects of disorder in the cuprate high-temperature superconductors.

Leiden physicists and international colleagues from Geneva and Barcelona have confirmed the mechanism that makes magic-angle graphene superconducting. This is a key step in elucidating high-temperature superconductivity, a decades-old mystery central to physics, which may lead to technological break…

Nature publishes an article on a paradoxical discovery in superconductivity. Physicists are searching for superconductivity at high temperatures so that less cooling is needed in for example MRI machines. News & Views article by Prof. Jan Zaanen in the same issue of August 19th.

Measurements on a superconducting material show an abrupt transition between a normal metal and a 'strange' metal. The really strange thing, however, is that this abruptness disappears when the temperature falls. 'We don't have any theoretical machinery for this', says theoretical physicist Jan Zaanen,…

If computers work on superconducting current, they won’t consume any energy. Leiden physicists have now gained control over a new type of superconducting memory elements. Publication in Nature Communications.

Superconducting devices such as SQUIDS (Superconducting Quantum Interferometry Device) can perform ultra-sensitive measurements of magnetic fields. Leiden physicsts invented a method to 3D-print these and other superconducting devices in minutes.

Triplet superconductivity refers to a condensate of equal-spin Cooper pairs (pairs of electrons with equal spin).

Majorana meets a mermaid

Physicist Milan Allan will build an instrument that will bring superconductivity research further. He has been awarded an ERC Consolidator Grant of 2 million euros over the next five years. With his PairNoise programme he aims to detect paired electrons as they occur just above the temperature at which…

Unconventional superconductors form one of the big mysteries in physics. Among them is strontium ruthenate, which stands out as a controversial superconductor. During his PhD, Leiden physicist Kaveh Lahabi has provided new insights into the nature of superconductivity in this material, leading to a…

The behaviour of strongly correlated electron systems, such as high-temperature superconductors, defies explanation in the language of ordinary quantum theory. A seemingly unrelated area of physics, string theory, might give physicists a better understanding of the weird behaviour of these kinds of…

Matthias Flór receives the KHMW Graduation Prize in Theoretical Physics for his master's thesis. His research on exotic superconductors at Leiden University and TU Delft struck a chord with the jury. The jury unanimously chose to award Flór noting that ‘he demonstrated impressive technical abilities…

We find ourselves in an era of transition, not just towards a more computing- and data-driven society but also away from unsustainable fossil fuels as an energy source.

This thesis presents insights from our study of various correlated electron systems with a scanning tunneling microscope (STM). In ordinary metals, electron-electron interactions exist, but get substantially screened due to the sheer number of electrons.

Online services are stored on servers in data centres. Remko Fermin researched methods to make the memory in data centres more energy efficient.

Since 2015 the United Nations have declared 11 February the International Day of Women and Girls in Science. Leiden University organized a public event for over a hundred visitors. In between a lecture on the building blocks of life and a talkshow on the impact of science on society, high school students…

Physicist Remko Fermin from Leiden University was awarded a Rubicon grant from NWO. He will use it to study superconducting diodes that could contribute to reducing the CO2 emission of data centres.

Koen Bastiaans and his colleagues discovered a new quantum liquid unlike anything ever seen. They did it by using a technique that can be compared to listening to the sound of raindrops falling on a roof. Publication in Science 29 October.

Experimental physicist Jan Aarts has received a FOM Projectruimte grant of 545,000 euro. He will use the budget to study the interaction between superconducting currents and ferromagnetism. In the future, this might lead to computer memory with negligible energy consumption.

In their quest for materials that conduct electricity without resistance at moderate temperatures, scientists usually work on their chemical make-up. Now Leiden physicists have come up with a radically new approach: pinching holes in a periodic pattern. Publication in SciPost.

In this thesis we use Josephson and noise scanning tunneling microscopy for the study of conventional, unconventional (iron-based) and disordered superconductors. On the one hand, Josephson scanning tunneling microscopy allows us to directly visualize the superfluid density with high spatial resolut…

Promotor: E.R. Eliel, Co-Promotor: M.J.A. de Dood

Research groups in the Quantum Matter & Optics programme investigate electronic properties of matter and light-matter interactions with emphasis on quantum information.

Electrons that spin synchronously around their axis, turn out to stay superconducting across large distances within magnetic chromium dioxide. Electric current from these electrons can flip small magnets, and its superconducting version could form the basis for a hard drive without energy loss. Publication…

Physics professor Jan Aarts starts a collaboration with chip manufacturer Intel to perform fundamental research in low-power, cryogenic computing.

For the first time, physicists have visualized the ‘melting’ of electrons inside a special class of insulators. It allows electrons to move freely and turns the insulator into a metal and possibly later into a superconductor. Publication in Nature Physics.

Our group explores the larger domain of quantum measurement. In particular we investigate two themes that are closely connected: The detection of specially prepared quantum states of light and understanding and characterizing quantum photon detectors.

In this thesis we study quantum transport phenomena on the nanometer scale, in two classes of materials: topological insulators with induced superconductivity and graphene superlattices.

STM scanning experiments on poorly conducting materials are challenging, and can cause a distortion effect. A new model corrects for this effect, allowing physicists to better study materials in their quest to understand unconventional superconductivity. Publication in Physical Review B as Editor’s…

Liquid nitrogen, frozen fruit and levitating market-goers. On Friday 8 April, visitors to the weekly market in the Merenwijk district were exposed to superconductivity. What is it exactly? And what does it look like? Young and old were impressed by the experiments demonstrated by Leiden students from…

The Leiden Institute of Physics has been awarded three out of twelve available grants from the FOM Projectruimte. Principal Investigators Milan Allan, Stefan Semrau and Carlo Beenakker all receive around 400,000 euro for their research.

A couple of years ago, theoretical physicist Carlo Beenakker tracked down the Majorana particles and inspired Leo Kouwenhoven from TU Delft to try to create them in a superconducting nano-structure. He succeeded in doing so in 2012, and the news made headlines around the world. But a lot of work still…

From the Big Bang to superconductivity. Many ground-breaking discoveries have been made in Leiden University’s long history.

As an alternative to the diving board shaped force sensor, we are now developing a magnetically levitated small superconducting particle – or ‘Lead Zeppelin'' – as our mechanical resonator. We explore routes towards detection of gravity between small objects.

Materials with strongly correlated electrons show some of the most mysterious and exotic phases of quantum matter, such as unconventional superconductivity, quantum criticality and strange metal phase.

Our cantilevers have a low intrinsic damping rate: this enables us to measure with low noise, since damping is proportionate to noise. However, when the magnet is close to the surface of a sample we want to study, we measure a much higher effective damping rate. This is caused by magnetic interaction…

In condensed matter systems electron-electron interactions, negligible in everyday metals, can dramatically alter the electronic behavior of the system. Examples of such altered behavior include high-temperature superconductivity and modulation of the electron density.

Schalm

This thesis presents the results of a study on the interfaces of insulating oxides with and without the insertion of a magnetic layer.