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Abstract

Many-body correlations are known to be responsible for a broad range of fascinating physical phenomena, introducing corrections that appear elusive at the single-particle level. An example of this is the Lifshitz transition that occurs as the Fermi surface topology changes when, e.g., Coulomb interaction effects break into the picture. The Fermi velocity renormalization can lead a type-II Weyl semimetal at mean-field level to become a trivial or a type-I Dirac material when correlations are accounted for, which is far from being obvious. In this paper, we scrutinize the band structure of NiTe2, a material that features a type-II Dirac point (DP) near the Fermi level, within the mean-field approach. Including GW-level correlations, our findings showcase anisotropic corrections on the Dirac carrier velocity exceeding 100% enhancements, underscoring the nuanced influence of electronic interactions in the band structure. We also consider type-II Dirac crossings in PtSe2 and PtTe2 and observe that, including many-body effects via GW, the band topology changes, featuring trivial topology and type-I Dirac crossings, respectively. Our findings highlight the necessity to evaluate the many-body effects on nontrivial bands, contributing essential insights into the broader exploration of many-body correlation effects in type-II DPs of condensed-matter systems.