Topological Insulators

Topological insulators are a new phase of quantum matter that emerges due to topological twists in the band structure of some materials. Discovered in 2008 in a single material, topological phases of matter now appear to be a pervasive feature of nature. The ideas underpinning the field are now applied in a diversity of topics ranging from acoustics to engineering and from electronics to photonics.

Van Heumen is now program leader of a new research program on correlated, topological phases: TOPCORE. The program focuses on developing new materials and subsequently modifying its properties using a set of external stimuli. Within the program we will study quantum phase transitions between different topological phases. tekst

Unconventional Superconductors

Unconventional superconductors like cuprates, iron-pnictides and heavy fermion superconductors are examples of emergent states of matter that derive their amazing properties from the collective behaviour of interacting electrons. Using transport experiments, ARPES, STM and optical spectroscopy we are searching for smoking-gun evidence of the interactions leading to superconducting instabilities.

Recently, much of our focus has been on the investigation of the so-called strange metal phase of the high Tc cuprates. Together with three other experimental groups and 4 theory groups we are investigating whether predictions made within the framework of the Anti-deSitter/conformal field theory correspondence. This research program is part of the FOM-NWO funded Strange Metal program.

The optics toolbox

Our lab uses both far-field and near-field spectroscpy to study the electronic properties of materials. The far-field optics lab features a Bruker vertex 80v inffrared spectrometer that covers the spectral range between 5 meV and 4.4 eV. This setup is mainly used to perform detailed temperature dependent studies using a dedicated optical cryostat. A recent addition is an 8 Tesla optical magnet, which is directly connected to the vertex 80v.