Paul Barklem, astronomy specialising in atomic processes in stellar atmospheres

Photo: Mikael Wallerstedt

How did our Milky Way galaxy form and evolve? Where and when were the various elements formed that make up the Earth and humans? Stars can be compared to fossils, and many of them show on their surfaces the composition of the gas from which they once were formed. By studying carefully selected stars, we can follow the history of the galaxy and the elements and obtain answers to these questions – a kind of archaeology with very long time horizons.

To do this, we need to measure the elemental composition of the stars. Because stars are so distant, the only way to investigate these fossils is by analysing the light that comes to Earth entirely “voluntarily”. Almost everything we know about stars comes from investigating the spectrum of stellar light. Each type of atom absorbs light at its special wavelengths, and we see this as spectral lines. In this way atoms in stellar atmospheres leave their fingerprints in the spectrum, from which we can measure the elemental composition.

My research deals with the theoretical calculations of atomic processes in stellar atmospheres. I and others use these calculations to accurately interpret the complex information of spectral lines and thereby stitch together a detailed and coherent picture of the history of the Milky Way, including an understanding of stars like the Sun, planets like Earth and their origins.

Annica Black-Schaffer, physics specialising in materials theory

Photo: Mikael Wallerstedt

To be able to describe all the different materials and phases of matter in nature, we need to understand how an almost infinite number of electrons interact with each other through the laws of quantum mechanics. As a theoretical physicist, I try to find simple, but universal models that explain the properties of whole families of different materials.

My research primarily deals with superconductivity, which is one of the few purely quantum mechanical phenomena we know of. A superconductor conducts electricity – that is, electrons – with no resistance at all. This occurs when electrons form what is known as a quantum condensate at low temperatures. I investigate superconductivity in materials we do not yet fully understand, neither why these materials are superconducting nor what their properties are. Among other things, I am interested in materials where the electron’s wave functions have a different structure, called topology. In topological superconductors, particles can emerge that behave like half electrons – or more accurately stated, the electron’s wave function is split into two completely separate parts. The half electrons are called Majorana fermions, and we have good expectations that their non-local nature can be used to build a stable quantum computer.

Herman Dürr, instrumentation and accelerators

Photo: Mikael Wallerstedt

My research focuses on the development of methods that make use of very short pulses (a millionth of a billionth of a second, called a femtosecond, 10-15 of a second) from modern laser and X-ray sources. When these light sources are combined with advanced spectroscopy, the researcher can examine the dynamics in condensed matter at the atomic length and time scales by which the most extreme macroscopic properties of materials are determined.

I am particularly interested in rapid transitions between magnetic and electronic states, especially what ultimately limits how quickly such transitions can occur. The processes that interest me are those crucial to the performance of materials used in information technology, for example. The X-ray pulses generated in a free electron laser provide completely new perspectives. With them you can achieve a precision in space and time that permits detailed studies of the fundamental processes. In addition to the work on light pulses at the department’s short pulse laser and at the major facilities in Stanford and Hamburg, I am developing an entirely new method that has the potential to provide unique insights on ultrafast dynamics and that will be of great importance for materials science, chemistry and structural biology. This method uses electron pulses that are very short and high-energy, moving close to the speed of light.

Oleg Kochukhov, astronomy specialising in stellar magnetic fields and activity

Photo: Mikael Wallerstedt

As the building blocks of galaxies and planetary hosts, stars are the central objects of astrophysics research. The nature of stellar magnetic fields and their influence on the stars themselves and their surroundings is one of the key problems in modern stellar physics.

The purpose of my research is to develop an understanding of stars through a detailed study of the origin and development of their magnetic fields. I use advanced polarisation measurement units at large telescopes to detect magnetic fields and then apply sophisticated computational techniques to reconstruct their topologies. By using this method, I obtain unique three-dimensional representations of distant stellar magnetic fields and flecks. I then position these maps on theoretical models of magnetised plasma to further develop the theory for a complete description of the stars and their environments.

In addition to forming a new cornerstone of stellar physics, this research provides us with an understanding of how the Sun’s magnetic activity develops over a period of time and how it affects the Earth’s climate and the biosphere.