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Observation of chiral fermions with a large topological charge and associated fermi-arc surface states in cosi

DOI: 10.1103/PhysRevLett.122.076402 DOI Help

Authors: Daichi Takane (Tohoku University) , Zhiwei Wang (University of Cologne) , Seigo Souma (Tohoku University) , Kosuke Nakayama (Tohoku University) , Takechika Nakamura (Tohoku University) , Hikaru Oinuma (Tohoku University) , Yuki Nakata (Tohoku University) , Hideaki Iwasawa (Diamond Light Source) , Cephise Cacho (Diamond Light Source; Central Laser Facility, Rutherford Appleton Laboratory) , Timur Kim (Diamond Light Source) , Koji Horiba (High Energy Accelerator Research Organization (KEK)) , Hiroshi Kumigashira (High Energy Accelerator Research Organization (KEK); Tohoku University) , Takashi Takahashi (Tohoku University) , Yoichi Ando (University of Cologne) , Takafumi Sato (Tohoku University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review Letters , VOL 122 , PAGES 076402

State: Published (Approved)
Published: February 2019
Diamond Proposal Number(s): 18839

Abstract: Topological semimetals materialize a new state of quantum matter where massless fermions protected by a specific crystal symmetry host exotic quantum phenomena. Distinct from well-known Dirac and Weyl fermions, structurally chiral topological semimetals are predicted to host new types of massless fermions characterized by a large topological charge, whereas such exotic fermions are yet to be experimentally established. Here, by using angle-resolved photoemission spectroscopy, we experimentally demonstrate that a transition-metal silicide CoSi hosts two types of chiral topological fermions, a spin-1 chiral fermion and a double Weyl fermion, in the center and corner of the bulk Brillouin zone, respectively. Intriguingly, we found that the bulk Fermi surfaces are purely composed of the energy bands related to these fermions. We also find the surface states connecting the Fermi surfaces associated with these fermions, suggesting the existence of the predicted Fermi-arc surface states. Our result provides the first experimental evidence for the chiral topological fermions beyond Dirac and Weyl fermions in condensed-matter systems, and paves the pathway toward realizing exotic electronic properties associated with unconventional chiral fermions.

Journal Keywords: Topological phases of matter; Dirac semimetal; Weyl semimetal; Angle-resolved photoemission spectroscopy; GGA

Subject Areas: Physics, Materials


Instruments: I05-ARPES

Other Facilities: KEK-PF; UVSOR