LEAPS-MPS: Unveiling the Interplay of Chiral Transport, Magnetism, and Topology in Weyl Magnets: A Magneto-Optical Investigation

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NON-TECHNICAL SUMMARYIn a solid, electrons exhibit many behaviors depending on their crystal structure and constituent elements. For semiconductors, electrons are heavy or light depending on a doping element. Massless electrons reside on graphene, an atomically thin honeycomb lattice of carbon. Recently, a new type of electron behavior has been discovered in a new class of materials called Weyl semimetals. The new electrons are massless, and their spin is locked in the direction of their motion. Particularly, the electrons have handedness or chirality, determining whether the electrons move forward or backward. Such chiral electrons offer the potential for new and high-speed electronics. This LEAPS-MPS project studies how the magnetization of bulk materials can affect chiral electron behavior measured by modulating the light polarization between left-handed and right-handed. This project aims to increase awareness and understanding of basic material science through hands-on research experience in optics and polarimetry for young students in the South Plains of West Texas. The monthly public outreach demonstrations in this project will engage and inspire the next generation of scientists and researchers, particularly K-12 students, by involving parents in their children’s education and creating a supportive environment for under-served student populations to pursue science and research. In addition, this project strengthens the physics curriculum for junior and senior undergraduate students who want to pursue advanced-degree programs in condensed matter physics.TECHNICAL SUMMARYChiral fermions are quasiparticles that arise in materials with two non-degenerate bands crossing – called Weyl points – at the Fermi level in three-dimensional momentum space. Weyl points, acting as monopoles and anti-monopoles of the magnetic field in momentum space, give rise to exotic properties such as Fermi arc surface states, the chiral anomaly, and the intrinsic anomalous Hall conductivity. The discovery of magnetic Weyl semimetals has generated considerable interest in the relationship between chiral fermions and magnetism. However, the complex interplay between magnetic texture and topological Weyl properties is not fully understood. This LEAPS-MPS award supports experimental research utilizing advanced magneto-optical techniques to investigate the intricate relationship between chiral transport, magnetic texture, and topology in magnetic Weyl semimetals. The proposed time-resolved magneto-optical measurement using nonlinear chiral pumping and broadband infrared Hall probing enables the simultaneous examination of non-equilibrium chiral states, local magnetic texture dynamics, and intrinsic anomalous Hall conductivity in magnetic Weyl semimetals. This project provides new insights into controlling topological functionalities through optical, electrical, and magnetic means, providing a foundation for investigating Weyl semimetals’ electronic structure and their potential applications in non-dissipative information control.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.