Radial Spin Texture of the Weyl Fermions in Chiral Tellurium
G. Gatti, Daniel Gosálbez-Martínez, Stepan S. Tsirkin, Mauro Fanciulli, Michele Puppin, S. Polishchuk, Simon Moser, Luc Testa, Edoardo Martino, Silvan Roth, Ph. Bugnon, Luca Moreschini, Aaron Bostwick, Chris Jozwiak, Eli Rotenberg, Giovanni Di Santo, L. Petaccia, I. Vobornik, Jun Fujii, Joeson Wong, Deep Jariwala, Harry A. Atwater, H. M. Rønnow, Majed Chergui, Oleg V. Yazyev, M. Grioni, A. Crepaldi
Abstract
Trigonal tellurium, a small-gap semiconductor with pronounced magneto-electric and magneto-optical responses, is among the simplest realizations of a chiral crystal. We have studied by spin- and angle-resolved photoelectron spectroscopy its unconventional electronic structure and unique spin texture. We identify Kramers-Weyl, composite, and accordionlike Weyl fermions, so far only predicted by theory, and show that the spin polarization is parallel to the wave vector along the lines in k space connecting high-symmetry points. Our results clarify the symmetries that enforce such spin texture in a chiral crystal, thus bringing new insight in the formation of a spin vectorial field more complex than the previously proposed hedgehog configuration. Our findings thus pave the way to a classification scheme for these exotic spin textures and their search in chiral crystals.