Max Planck Institute for Chemical Physics of Solids

Experiments show that the heavy fermion compound YbRh₂Si₂ undergoes a spectacular electro-nuclear phase transition into a modulated magnetic state at a temperature as low as 1.5 mK. In a just published paper, an international team of scientists from the UK (Royal Holloway University of London) and Germany (Goethe University Frankfurt, MPI-CPfS Dresden) demonstrated that in YbRh₂Si₂, at T_A = 1.5 mK, the tiny nuclear moments profoundly change an electronic magnetic state formed at a much higher temperature  T_N = 70.5 mK.  

Roughly 90 percent of all materials can have electronic states on surfaces which differ from those in their bulk

A giant anomalous Nernst effect was found in YbMnBi₂

A novel material has been discovered that is characterised by the coupling of a charge density wave with the topology of the electronic structure.

Researchers demonstrate new high-throughput method for discovering magnetic topology

It is frequently only the development of new materials that makes technological advances possible, whether in the areas of energy supply or information technology. With the Heusler compounds, Claudia Felser, Director at the Max Planck Institute for Chemical Physics of Solids in Dresden, uncovered a rich source of materials that offer promising properties for a variety of applications.

Electric cables that routinely conduct electricity without loss – physicists have been motivated by this idea ever since superconductivity was discovered 100 years ago.

Even the most efficient motor generates more heat than propulsion. However, thermoelectric generators could convert some of this unused energy into electricity. Scientists are currently searching for suitable materials.

Using a recently developed formalism, titled topological quantum chemistry (TQC) and magnetic TQC, we carry out a high-throughput search of topological materials in well known databases, such as Inorganic Crystal Structure Database. We identified as many as 20000 materials that display topological features and another ~100 new topological magnetic materials. Herein, we review this discovery and provide insights for future material search directions.

The Quantum Hall Effect (QHE) in two-dimensional (2D) metals is a macroscopic quantum phenomenon and has helped to solve many important aspects of quantum physics. In common three-dimensional (3D) metals, the QHE is usually forbidden, because the third dimension destroys the quantization. However, our studies on the 3D metals ZrTe ₅ and HfTe ₅ show that their Hall resistance can be quasi-quantized if there are enough electrons in the materials. This makes the Hall effect in ZrTe ₅ and HfTe ₅ a real 3D counterpart to QHE in 2D systems.

The search for new quantum materials with novel properties is often focused on materials containing transition-metal or rare-earth elements. The presence of the atomic-like d or f orbitals provides a fruitful playground to generate novel phenomena. In order to efficiently design and tune the materials, it is essential to identify the d or f orbitals that actively participate in the formation of the ground state. Here we developed a new experimental method that circumvents the need for theory and instead provides the information as measured.

Tantalum has one of the largest quadrupole moments among all elements which makes it a rather useful local probe for excitations of Weyl fermions in the new Weyl semimetal TaP. We found three NQR lines in a good agreement with theoretical calculations including spin orbit coupling. The temperature dependence of the spin lattice relaxation rate is attributed to the magnetic excitations at the Weyl nodes and a good agreement with predictions from theory could be found. The microscopic magnetic resonance techniques therefore provide new insides into the class of Weyl semimetals.

Every musical instrument has its own sound with a frequency spectrum that is determined by the shape of the instrument. In analogy to that, every metal has its characteristic frequency spectrum reflecting the properties of its electrons. Our investigation of the quantum sound of electrons in the metal PdRhO2 shows that electrons move quickly in the crystallographic planes whereas they hardly move perpendicular to the planes. The quantum music sounds slightly differently than expected and will help understand the particular hydrodynamic transport properties of electrons in these metals.