Researchers Arka Ghosh, Sushmita Saha, and Alestin Mawrie from the Indian Institute of Science Education and Research, Kolkata, have published a study in the journal Physical Review Letters that explores the quantum-mechanical theory behind negative magnetoresistance in multi-Weyl semimetals. Their work could have significant implications for the energy sector, particularly in the development of advanced materials for energy storage and transmission.
Negative magnetoresistance refers to the phenomenon where the resistance of a material decreases when a magnetic field is applied. In this study, the researchers focused on multi-Weyl semimetals, a class of materials that exhibit unique electronic properties due to their unusual band structure. The team developed a fully quantum-mechanical theory to explain how negative magnetoresistance occurs in these materials when an electric field is applied parallel to a magnetic field, a configuration that activates the chiral anomaly.
The chiral anomaly is a phenomenon in particle physics that has been shown to play a role in the electronic properties of certain materials. In multi-Weyl semimetals, the chiral anomaly leads to the emergence of multiple chiral Landau levels, which are quantized energy levels that arise due to the interaction between the material’s electrons and the applied magnetic field. These chiral Landau levels have unidirectional dispersion, meaning that they only allow electrons to move in one direction, and are fixed by the node’s monopole charge.
As the magnetic field is increased, individual chiral branches successively cross the Fermi energy, which is the energy level at which electrons can freely move through the material. This crossing produces discrete slope changes in the longitudinal conductivity and a step-like negative magnetoresistance. The researchers found that this quantized evolution provides a direct experimental signature of multi-Weyl topology, which is the unique geometric structure of the material’s band structure.
The researchers also found that bulk Landau levels, which are energy levels that arise due to the quantization of electron orbits in a magnetic field, contribute only at very low fields due to strong disorder scattering. Disorder scattering refers to the scattering of electrons by impurities or defects in the material, which can disrupt the formation of Landau levels. The researchers found that bulk Landau levels do not affect the anomaly-driven regime, which is the range of magnetic field strengths where the chiral anomaly is active.
Overall, this study provides a unified, fully quantum-mechanical framework for understanding negative magnetoresistance in multi-Weyl semimetals. The researchers’ findings could have practical applications in the energy sector, particularly in the development of advanced materials for energy storage and transmission. For example, materials with negative magnetoresistance could be used to create more efficient power lines or to develop new types of batteries that can store and release energy more quickly. The research was published in Physical Review Letters.
This article is based on research available at arXiv.