New details of the Fermi surface of 2H-NbSe2 revealed by quantum oscillations in the magnetostriction

The layered charge-density wave (CDW) superconductor 2H-NbSe2 (TS=7.2 K) is the very first material in which quantum oscillations have been observed in the mixed state by means of magnetization and magnetostriction measurements. The magnetostriction technique offers the advantage that quantum oscillations are particularly pronounced, which is due to pressure sensitivity of the relevant cross-section of the Fermi surface. Moreover, measurements can be performed for a field oriented along the crystallographic axis in contrast to the torque technique that is routinely used. Here we present magnetostriction measurement on a high-quality single-crystalline sample for temperatures 0.25-8.0 K using a sensitive capacitance dilatometer. Two oscillation frequencies are observed at the lowest temperatures for the in-plane orientation of the applied magnetic field. These new data reveal that the Fermi-surface sheet in the first Brillouin zone has two cross-sections, rather than the conventional pan-cake shape.