New insights into magnetic quantum effects in solids
by Staff Writers
Berlin, Germany (SPX) Jan 23, 2019
Atoms and molecules in crystalline solids are arranged in regular three-dimensional lattices. The atoms interact with each other via various forces, finally reaching a state of minimum energy.
Near absolute zero, the lattice oscillations freeze, so that interactions between electron spins dominate. A particularly interesting case occurs when the spins cannot all align at the same time to reach a state of lowest energy. This results in a frustrated system in which the spins are almost completely disordered and are therefore referred to as a spin liquid.
One of the leading models for studying 3D frustrated quantum magnets is the Heisenberg model on a pyrochlore lattice - a simple cubic crystal structure (see illustration). Nevertheless, it has so far been extremely difficult to derive practical predictions, i.e. for specific materials and temperatures, from this theoretical model.
Different spin values
It is possible with this new method to vary the spin value of the lattice atoms as well as the temperature and other interaction parameters, and to calculate the parameter ranges in which novel magnetic quantum effects occur. The calculations were carried out at the Leibniz Supercomputing Centre (LRZ) in Munich.
Quantum effects only for small spins
These quantum effects are most pronounced at the smallest possible spin (spin value 1/2). However, spin systems in the crystal structure investigated by the teams already behave almost completely like classical physical systems at spin values of 1.5 and above.
The work published deepens our understanding of solids and contributes to the systematic advancement of the search for 3D spin fluids in quantum materials.
Proposed engineering method could help make buildings and bridges safer
Ishikawa, Japan (SPX) Jan 18, 2019
Pearlitic steel, or pearlite, is one of the strongest materials in the world and can be made into thin and long wires. The strength of pearlite allows it to sustain very heavy weight, however what makes it special is its ability to stretch and contract without breaking (ductility). Ductility is important for building bridges, as even if a material is strong enough to support heavy weight, it can break when subjected to stretching if it is not ductile enough. This is why structures made of concrete ... read more
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