De Haas-van Alphen oscillations in extremely type-II nearly 2D superconductors

Abstract

Two-Dimensional (2D) electron systems are expected to exhibit strikingly new phenomena in the superconducting state when placed under strong quantizing magnetic fields. We analyze the nature of the field dependent magnetization around the normal-superconducting phase boundary at low temperatures. Under ideal conditions (i.e. for sufficiently weak electron scattering by sideorder) both the normal and the superconducting components of the magnetization are in the 2D quantum diamagnetic regime, i.e. both are purely oscillatory and of the same order of magnitude. Unlike the normal 2D magnetooscillations, however, which are generated only by the two Landau levels adjacent to the Fermi energy, the superconducting ones involve many Landau levels around the Fermi energy and have a gapless structure. In contrast to the usual dHvA oscillations pattern, the amplitude of the oscillations' envelop is shown to increase with the decreasing field below H c2(T), up to a maximum located at lower fields for lower Temperatures. Under the conditions of zero spin splitting the system may crossover into a new (reentrant) superconducting state, driven by the (resonant) pairing of many electrons within a single Landau level.