BESSY II: Experimental verification of an exotic quantum phase in Au2Pb
The figure shows the measured energy-momentum relationship for Au2Pb. The linear behavior is evidence for a Dirac semimetal. In addition, a Lifshitz transition is observed: At temperatures 223 K and below, the electrons behave like positively charged particles, whereas at room temperature they behave like negatively charged ones. © HZB
A team of HZB has investigated the electronic structure of Au2Pb at BESSY II by angle-resolved photoemission spectroscopy across a wide temperature range: The results are in accordance with the electronic structure of a three-dimensional topological Dirac semimetal, in agreement with theoretical calculations.
The experimental data unveil some very special features linked to a Lifshitz transition. The study broadens the range of currently known materials exhibiting three-dimensional Dirac phases, and the observed Lifshitz transition demonstrates a viable mechanism to switch the charge carrier type in electric transport without the need for external doping. Moreover, the material becomes interesting as candidate for the realization of a topological superconductor.
The study which includes theory from San Sebastian and synthesis from Princeton was highlighted as Editor's Suggestion in the journal Physical Review Letters.
- Largest magnetic anisotropy of a molecule measured at BESSY IIAt the Berlin synchrotron radiation source BESSY II, the largest magnetic anisotropy of a single molecule ever measured experimentally has been determined. The larger this anisotropy is, the better a molecule is suited as a molecular nanomagnet. Such nanomagnets have a wide range of potential applications, for example, in energy-efficient data storage. Researchers from the Max Planck Institute for Kohlenforschung (MPI KOFO), the Joint Lab EPR4Energy of the Max Planck Institute for Chemical Energy Conversion (MPI CEC) and the Helmholtz-Zentrum Berlin were involved in the study.
- Ernst Eckhard Koch Prize and Synchrotron Radiation Innovation AwardThis year, the Friends of Helmholtz-Zentrum Berlin (Freundeskreis des HZB e. V.) awarded the Ernst Eckhard Koch Prize to Dr. Dieter Skroblin of the Technische Universität Berlin for his outstanding doctoral thesis. The European Innovation Award Synchrotron Radiation went to Dr. Manfred Faubel from the Max Planck Institute for Dynamics and Self-Organization in Göttingen and Dr. Bernd Winter from the Fritz Haber Institute in Berlin. The award ceremony took place at this year's HZB user meeting.
- Modernisation of BESSY II+ light sourceThe focus of the User Meeting 2024: Helmholtz-Zentrum Berlin (HZB) presents the BESSY II+ upgrade programme. It enables world-class research at BESSY II to be further expanded and new concepts to be tested with regard to the successor source BESSY III.