Correlation-driven electron-hole instability in nodal-line semimetal ZrSiS

ZrSiS is an emerging material, which belongs to the class of 3D materials that feature a nodal line in the electronic band structure $[$1$]$. Recent experimental observations reveal an unconventional mass enhancement of quasiparticles in ZrSiS $[$2$]$, which suggests the importance of electron correlation effects in this material. Here, we study many-body effects in ZrSiS using a combination of first-principles calculations and model approaches, taking the correlation effects perturbatively. We show that at moderately low temperatures ZrSiS exhibit electron-hole instability, leading to the formation of a pseudogap in the electronic spectrum. The results can be understood in terms of Coulomb-interaction-assisted electron-hole pairing reminiscent to that of a conventional superconductor.