New at Campus Wannsee: CoreLab Quantum Materials
This optical zone melting furnace is producing large single crystals. © M. Setzpfandt/HZB
A Laue apparatus is used for precise alignment of the crystals. © M. Setzpfandt/HZB
Phase transitions can be detetcted by measuring transport properties of the sample. © M. Setzpfandt/HZB
Helmholtz-Zentrum Berlin has expanded its series of CoreLabs for energy materials research. In addition to the five established CoreLabs, it has now set up a CoreLab for Quantum Materials. A research team from the HZB Institute for Quantum Phenomena in New Materials is responsible for the CoreLab and its modern equipment. The CoreLab is also open to experimenters from other research institutes.
Quantum phenomena are typically easiest to observe within perfect single crystals at very low temperatures. A team led by Prof. Dr. Bella Lake and Dr. Konrad Siemensmeyer has set up a dedicated CoreLab for Quantum Materials for producing and experimenting with such single crystals in the laboratory, or for preparing them for measurements at the neutron source BER II or the synchrotron light source BESSY II. External researchers are also welcome to use this CoreLab and benefit from the expertise of the HZB team.
Growth and preparation of single crystals
In many cases, the materials of interest are initially produced as microcrystalline powders and not as single crystals. Even the process of synthesising these powders is often difficult. It is therefore a key topic at this HZB CoreLab. In a powerful optical zone melting furnace, powder samples can be regrown as larger single crystals, which yield far more meaningful experimental results. Growing single crystals from powder samples requires a great deal of experience, which HZB possesses. A Laue apparatus is used for precise alignment of the crystals. Next, the crystals are cut in orientation with a wire saw or their surfaces polished in preparation for further experiments. The methods are highly flexible and suitable for all possible experiments. Samples are easily prepared here for experiments at the neutron source, at BESSY II, or in the lab. Less experienced users are closely supervised to ensure the success of their experiments.
Transport properties and phase transitions
Another room provides high magnetic fields, low temperatures with two “Physical Property Measurement Systems” and a sensitive SQUID magnetometer. These allow the measurement of transport properties such as thermal conductivity, magnetisation and specific heats of materials. Measuring these properties renders so-called phase transitions visible. These phase transitions have a correlation with quantum physical laws and indicate the formation of new structures within the material.
CoreLabs for users in academia and industry
As an operator of large facilities, HZB has great experience in organising external user operation. HZB is now also introducing this experience into the operation of its CoreLabs, which are equipped with latest generation, and sometimes unique, instruments and equipment for analysing and synthesising energy materials. International experimental guests and partners from industry are equally welcome here.
- Long-term stability for perovskite solar cells: a big step forwardPerovskite solar cells are inexpensive to produce and generate a high amount of electric power per surface area. However, they are not yet stable enough, losing efficiency more rapidly than the silicon market standard. Now, an international team led by Prof. Dr. Antonio Abate has dramatically increased their stability by applying a novel coating to the interface between the surface of the perovskite and the top contact layer. This has even boosted efficiency to almost 27%, which represents the state-of-the-art. After 1,200 hours of continuous operation under standard illumination, no decrease in efficiency was observed. The study involved research teams from China, Italy, Switzerland and Germany and has been published in Nature Photonics.
- Energy of charge carrier pairs in cuprate compoundsHigh-temperature superconductivity is still not fully understood. Now, an international research team at BESSY II has measured the energy of charge carrier pairs in undoped La₂CuO₄. Their findings revealed that the interaction energies within the potentially superconducting copper oxide layers are significantly lower than those in the insulating lanthanum oxide layers. These results contribute to a better understanding of high-temperature superconductivity and could also be relevant for research into other functional materials.
- Electrocatalysis with dual functionality – an overviewHybrid electrocatalysts can produce green hydrogen, for example, and valuable organic compounds simultaneously. This promises economically viable applications. However, the complex catalytic reactions involved in producing organic compounds are not yet fully understood. Modern X-ray methods at synchrotron sources such as BESSY II, enable catalyst materials and the reactions occurring on their surfaces to be analysed in real time, in situ and under real operating conditions. This provides insights that can be used for targeted optimisation. A team has now published an overview of the current state of knowledge in Nature Reviews Chemistry.