https://doi.org/10.1140/epjb/s10051-021-00091-1
Regular Article - Solid State and Materials
Electronic correlation effect on nontrivial topological fermions in CoSi
1
School of Basic Sciences, Indian Institute of Technology Mandi, 175075, Kamand, Himachal Pradesh, India
2
School of Engineering, Indian Institute of Technology Mandi, 175075, Kamand, Himachal Pradesh, India
Received:
21
January
2021
Accepted:
26
March
2021
Published online:
10
April
2021
The present study has been carried out to understand the effect of electronic correlations on the recently found fermions in CoSi. For which the spectral functions of bulk and (001) surface of CoSi have been investigated using DFT + DMFT advanced methodology at T = 100 K with and without inclusion of spin–orbit coupling (SOC). The Co 
+ 
and 
bands seem to contribute at threefold degenerate 
point. On the other hand, fourfold degenerate R point seems to posses maximum of Co 
orbitals and minimum of 
orbitals. However, SOC and electronic correlations appear to modify the nature of bands involved at point. DFT + DMFT calculations for the bulk states have shown one extra hole pocket at M point. Incoherent features seem to be possessed by mostly Co orbitals in the spectra of bulk CoSi. The existence of both coherent and incoherent features indicates the presence of quasiparticle–quasiparticle (QP–QP) interactions which is eventually affecting the lifetime (
) of exotic fermionic QPs. For instance, the calculated for QPs at 
− 3 and − 186 mev are found to be 
s and 
s, respectively, when SOC is not considered. However, 
corrections have shown for spin-1 fermionic QP at to be infinite while for double Weyl fermionic QP at R point to be s. Their effective masses (
) have also been calculated as 
1.60 and 1.64 at and R points, respectively. Furthermore, the spectral functions at T = 100 K of (001) surface have also shown both coherent and incoherent features. Consequently, at 
= 0 for surface states, has been calculated of the order 
s for both without SOC and with SOC inclusions.
© The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature 2021
