Damping of the de Haas-van Alphen oscillations in the superconducting state of MgB_2

TL;DR

This study investigates how superconductivity in MgB₂ affects de Haas-van Alphen oscillations, revealing that the damping exceeds current theoretical predictions and that the π band gap persists up to the upper critical field.

Contribution

The paper provides experimental evidence of enhanced damping of dHvA oscillations in MgB₂'s superconducting state and compares it with existing theories, highlighting significant discrepancies.

Findings

dHvA oscillations are observed below Hc2 in MgB₂

Superconducting gap causes additional damping beyond conventional models

Recent theories underestimate damping effects in MgB₂

Abstract

The de Haas-van Alphen (dHvA) signal arising from orbits on the $\pi$ Fermi surface sheet of the two-gap superconductor MgB$_2$ has been observed in the vortex state below $H_{c2}$. An extra attenuation of the dHvA signal, beyond those effects described in the conventional Lifshitz-Kosevich expression, is seen due to the opening of the superconducting gap. Our data show that the $\pi$ band gap is still present up to $H_{c2}$. The data are compared to current theories of dHvA oscillations in the superconducting state which allow us to extract estimates for the evolution of the $\pi$ band gap with magnetic field. Contrary to results for other materials, we find that the most recent theories dramatically underestimate the damping in MgB$_2$.