Sahal Kaushik, Stony Brook University
Late News: Tunable Chiral Symmetry Breaking in Symmetric Weyl Materials
Written by Jessalyn Hui Ying Low
Asymmetric Weyl materials have an inherently chiral crystal structure, but lack symmetry between left- and right-handed fermions. Due to these properties, they exhibit many unique phenomena such as the quantized circular photogalvanic effect, yet are much rarer as compared to symmetric Weyl materials. In this talk, Sahal Kaushik shows how by applying external perturbations, in particular external magnetic field, chiral symmetry in symmetric Weyl materials can be broken to become asymmetric.
With a focus on materials with the -43m (Td) point group, Kaushik explains that for chiral symmetry breaking, it is insufficient to break only reflection symmetries as this could induce false chirality. Rather, all combinations of reflection and time reversal should be broken. Therefore, for a measure of true chirality, the magnitude of the magnetic field must be different along all three directions, implying that chirality will be broken when the magnetic field is applied along low symmetry directions like  and not high symmetry directions like  and . It was shown that when magnetic field was applied along low symmetry directions, left- and right-handed Weyl cones indeed showed different energies, velocities, and tilts. These symmetry breaking parameters were influenced by magnitude and direction of the magnetic field. Notably, as the direction of magnetic field increased in asymmetry, the discrepancy between left- and right-handed Weyl cones increased, highlighting how chirality symmetry breaking in Weyl materials can be tuned.