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

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

Promotor: J. Aarts

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

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

In my group (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. J. Zaanen & Prof.dr. K.E. Schalm

In this work, we illustrate unconventional approaches towards the fabrication of edge functionalized graphene nanostructures and bidimensional architectures in polymeric and metallic supports, with an outlook towards molecular sensing devices.

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.

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.

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.

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…

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.

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…

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,…

Majorana meets a mermaid

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.

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…

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…

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.

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…

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.

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.

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

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…

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.

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.

Making the most vibration-free, cryogenic scanning tunneling microscope in the world. A bold mission, but one that PhD candidate Irene Battisti successfully executed together with the Fine Mechanical Department. The new microscope might shed light on how unconventional superconductivity works. PhD Defence…

We don’t understand how some materials become superconducting at relatively high temperatures. Leiden physicists have now found a surprising connection with auxiliary black holes. It enables us to use our knowledge of black holes on the mystery of high-temperature superconductivity. Publication in Nature…

Jan Zaanen, Professor in Theoretical Physics of condensed material, has been awarded a Spinoza prize. His pioneering ideas about the collective behaviour of quantum particles and high temperature superconductivity have often given him the reputation of being something of a rebel.

High-temperature superconductivity is one of the big mysteries in physics. Milan Allan’s research group used a Josephson Scanning Tunneling Microscope to image spatial variations of superconducting particles for the first time, and published about it in the journal Nature.

String theory has come under fire in recent years. Promises have been made that have not been lived up to. Leiden theoretical physicists have now for the first time used string theory to describe a physical phenomenon. Their discovery has been reported this week in 'Science'.

On a referendum held on May 21, 2006, 55.5% of voters in Montenegro voted in favor of their country’s independence. While in numerical terms the outcome shows overwhelming support for independent Montenegro, from a normative standpoint it was a narrow win. The normative framework that regulated rules…

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.

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.

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.

PhD Defence

Promotor: Prof.dr.ir. J.W.M. Hilgenkamp, Prof.dr. J. van den Brink

In this thesis unconventional tools based on fluidic interfaces were developed to study the surface and interfacial chemistry of graphene, to characterize the intrinsic properties of graphene, to disentangle the effects of substrate and of the environmental factors, and to improve handling protocols…

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…

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

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…

The Copenhagen interpretation of quantum mechanics states that a measurement collapses a wavefunction onto an eigenstate of the corresponding measurement operator.

Schalm

PhD Defence

Leiden physicists have developed a way to address how accurately a superconducting single photon detector (SSPD) can be characterized by detector tomography. SSPDs are not fully understood, and tomography is a key element to determine how these devices detect light. A better understanding of these detectors…

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