Quantifying quasiparticle chirality in a chiral topological semimetal
Abstract
Recently, the projection of the electron's spin on its crystal momentum has been proposed as a metric to quantify electronic chirality of Bloch states in crystals, which is expected to affect a wide range of physical properties, such as magnetoelectric and optical responses. However, a direct experimental quantification of this chirality metric over an entire iso-energy surface has remained elusive. Here, we have used spin- and angle-resolved photoemission spectroscopy to directly probe the electronic chirality by measuring the bulk spin texture of Kramers-Weyl and Weyl cones in RhSi, a chiral topological semimetal with strong spin-orbit coupling (SOC). After quantifying the SOC splitting of Weyl cones, we determine their spin direction along different azimuthal angles to extract energy dependent the deviations (up to ~40{\deg}) from perfect parallel spin-momentum locking. From these deviations we define an energy-dependent normalized electron chirality density (NECD), a directly accessible metric of bulk electronic chirality. In RhSi, the NECD decreases from 1 at the Kramers-Weyl point to ~0.8 at ~200 meV below it. Finally, we show that this experimentally grounded NECD provides predictive power for magneto-optical and transport responses of chiral materials, exemplified by the longitudinal Edelstein effect.
Cite
@article{arxiv.2603.14640,
title = {Quantifying quasiparticle chirality in a chiral topological semimetal},
author = {Jiaju Wang and Jaime Sánchez-Barriga and Amit Kumar and Markel Pardo-Almanza and Jorge Cardenas-Gamboa and Iñigo Robredo and Chandra Shekhar and Daiyu Geng and Emily C. McFarlane and Martin Trautmann and Enrico Della Valle and Moritz Hoesch and Meng-Jie Huang and Jens Buck and Vladimir N. Strocov and Annika Johansson and Stuart S. P. Parkin and Claudia Felser and Maia G. Vergniory and Niels B. M. Schröter},
journal= {arXiv preprint arXiv:2603.14640},
year = {2026}
}