Robust structure symmetry and electronic band structure of the chiral topological semimetal CoSi against high pressure

The chiral crystal symmetry in the transition metal monosilicide CoSi plays a requisite role in protecting the multifold chiral fermion and its robustness to external pressures is very crucial for the applications of this important material. By performing high-pressure X-ray diffraction and electronic transport measurements, we reveal that the chiral structure of CoSi is robust against external pressure up to ~ 39 GPa. The ab initio calculations unveil that the external pressure negligibly influences the electric band structure in which the threefold degenerate spin-1 chiral fermion at the Gamma point and the fourfold degenerate charge-2 Dirac node at the R point in the Brillouin zone could be well preserved. Through studying the high pressure effects on the unconventional topological semimetal CoSi, our results have unveiled robust multifold chiral fermions under the high pressure.