TITLE : Quantum Oscillations in Nodal-line semimetals

ABSTRACT :

Nodal line semimetals (NLSM) exhibit interesting quantum oscillation characteristics when acted upon by strong magnetic fields. We consider a NLSM continuum model to report the features of the Landau level spectra and the fluctuations in the Fermi level as the field in a direction perpendicular to the nodal plane is varied through. Based on the results on parallel magnetization, we demonstrate the growth of quantum oscillation with field strength as well as its constancy in period when plotted against 1/B. We find that the density of states which show a series of peaks in succession, witness bifurcation of those peaks due to the Zeeman effect. For field normal to nodal plane, such bifurcations are discernible only if the electron effective mass is considerably smaller than its free value, which usually happens in these systems. Though a reduced effective mass m* causes the Zeeman splitting to become small compared to Landau level spacings, experimental results indicate a manyfold increase in the Lande g factor which again amplifies the Zeeman contribution. Interestingly, topologically nontrivial oscillations are witnessed at low energies when the magnetic field lies in the nodal plane. There the density of state peaks do not repeat periodically with energy anymore. The spectra become more spread out and the Zeeman splittings become less prominent. We find the low energy topological regime, that appears with such an in-plane field set up, to shrink further with reduced m* values. However, such a topological regime can be stretched out in case there are smaller Fermi velocities for electrons in the direction normal to the nodal plane. Moreover, an oscillatory field variation, as opposed to a steady one, has an interesting impact on the quantum oscillation phenomena with the Landau tubes crossing the Fermi surface externally two times per cycle. With proper parameters chosen, one can engineer topological transitions to occur periodically in such systems as an in-plane oscillating field is swept through its cycles.

MEETING DETAILS :

Speaker: Dr. Satyaki Kar

Venue: A4 Conference room

Date and Time: November 9th, 2021 4:00pm.