Correlation induced instability in topological nodal-line semimetal ZrSiS

Quantum phase transition hosts a quantum criticality around which the collective low-energy excitations are governed by quantum fluctuations. At this quantum critical regime, fluctuations alter the quasiparticle characteristics introducing some instabilities in the system. The experimental signatures of quantum criticality in topological Dirac materials are sparse. Here, we report the transport studies on nodal line semimetal ZrSiS, which is predicted to own excitonic instability at quantum criticality. Our quantum oscillation studies demonstrate a significant change in Berry phase at higher magnetic fields revealing a field-induced gap modification at the nodal line. Notably, the quasiparticle effective mass executes unique field-dependent oscillations, which is unexplainable from present theories. The temperature dependent oscillation amplitude dramatically departs from conventional Lifshitz-Kosevich theory. These unusual phenomena along with a zero field resistivity upturn collectively suggest the possibility of ZrSiS lying at the excitonic instability. Our findings will engender the systematic exploration of correlation induced phenomenon in topological materials.