Erik obtains Senior Qualification Education

On March 3, 2022 I obtained my senior qualification education. To achieve this I started a project to streamline and reorganize the exit qualifications of the Advanced Matter & Energy Physics program. Together with a large group of lecturers we discussed the various study lines of the program and proposed and implemented an update of the program. The project serves as blueprint for a revision of the entire Physics and Astronomy program.

Probing the strange metal with optical spectroscopy

One of the key mysteries in the cuprate phase diagram is the strange metallic phase, which features a variety of anomalous electronic properties. In recent years, various (magneto-) transport experiments have reported a singular behavior around p = 0.2 holes/Cu. In a new publication, we introduce a phenomenological 'generalized' interband transition to describe the incoherent optical response across the cuprate phase diagram. This allows us to directly connect optics to transport experiments.

We show that the doping and temperature evolution of the resistivity can be fully understood from changes in the Drude momentum relaxation rate. At the same time, the carrier density displays a continuous and gradual evolution across the phase diagram.

More can be read in our manuscript in Physical Review B.

ENW-GROOT awarded to van Heumen and de Visser

NWO has awarded a grant of € 3 million within the open competition to the TOPCORE consortium led by UvA-physicist Dr. Erik van Heumen.

The program aims to investigate materials with which the researchers want to find novel ways to gain control over their electrical properties.

Next to Van Heumen, also Dr. Anne de Visser from the UvA-Institute of Physics is involved in the consortium that consists of 9 other researchers from in total 6 Dutch Universities. The consortium aims to kickstart a new field of research, with the goal to develop novel materials that change their electrical or magnetic properties strongly under small perturbations such as pressure, temperature or applied electric field. To achieve this goal, the TOPCORE program combines groundbreaking ideas from the mathematical field of topology with experiments and theoretical investigations of recently discovered materials. More information about the open competition can be found on the NWO website.

Strange metal Workshop 2020: Space and Order

The NWO funded strange metal program is organizing a workshop at the Lorentz center@Snellius from January 6, 2020 to January 10, 2020.

The program revolves around the spatial symmetries and the understanding of emergent spatial structures in both experimental observations and holographic treatment. Together with Christiana Pantelidou, Alexander Krikun and Milan Allen we have been able to attract funding from ICAM-I2CAM to host this workshop. The workshop details can be found on the Strange metal program website.

Optical properties of PdTe2 in Phys. Rev. Materials

We have published the first high resolution optical spectroscopy data on PdTe2. We demonstrate that the temperature dependence of the scattering rate can be explained by the presence of a vanHove singularity close to the Fermi level.

PdTe2 has recently attracted much attention for the possible existence of a low temperature, topological superconducting state. In a new publication in Physical Review Materials we report high resolution infrared, optical data as function of temperature. Our high quality reflectivity data allows us to study the optical conductivity of the normal state in detail. We observe a sharp Drude response and several interband transitions that can be associated with the bands forming the Dirac metal phase in this material.

From an analysis of the complex optical conductivity we extract the frequency and temperature dependent scattering rate, 1/τ(ω,Τ).

Scattering rate

We find that the scattering rate decreases to a value below our detection limit below 50 K. The paper explains that this points to the presence of a van Hove singularity within 20-30 meV of the Fermi level. This observation has important ramifications for the mechanism of superconductivity in these materials and possibly could be evidence for an important role of the density of states in determining the superconducting properties of transition metal di-chalcogenides.

Scattering rate collapse driven by a van Hove singularity in the Dirac semimetal PdTe2 Erik van Heumen, Maarten Berben, Linda Neubrand, and Yingkai Huang Phys. Rev. Materials 3, 114202 (2019)