Giant nonlinear response due to unconventional magneto-oscillations in nodal-line semimetals

Quantum oscillations in magnetoconductance of a material at low temperatures and presence an intense magnetic field are described by the Shubnikov de Haas (SdH) effect. It is widely assumed to be hallmark Fermi surface given metal. In contrast canonical situation, we identify exotic oscillation nonlinear responses three-dimensional nodal line semimetals (NLSMs) which persist even where typical SdH-like vanish. This occurs due periodic gap-closing pair Landau levels zero energy with variation field. The emergence remarkable fingerprint ring dispersion corresponding frequency can used determine radius ring. Using Boltzmann equation, calculate second harmonic generation under parallel DC electric strong fields. conductivity diverges gap closing condition leading giant response NLSMs.