Spin-zero anomaly in the magnetic quantum oscillations of a two-dimensional metal

TL;DR

This paper investigates anomalous spin-splitting zeros in the dHvA signal of a quasi-two-dimensional superconductor, revealing deviations from standard theory explained by chemical potential oscillations.

Contribution

It demonstrates that chemical potential oscillations account for the anomalous behavior of spin-splitting zeros in magnetic quantum oscillations.

Findings

Deviations from Lifshitz-Kosevich theory in second harmonic amplitude.

Confirmation of oscillating chemical potential through wave-shape analysis.

Standard LK behavior observed in fundamental dHvA and Shubnikov-de Haas signals.

Abstract

We report on an anomalous behavior of the spin-splitting zeros in the de Haas-van Alphen (dHvA) signal of a quasi-two-dimensional organic superconductor. The zeros as well as the angular dependence of the amplitude of the second harmonic deviate remarkably from the standard Lifshitz-Kosevich (LK) prediction. In contrast, the angular dependence of the fundamental dHvA amplitude as well as the spin-splitting zeros of the Shubnikov-de Haas signal follow the LK theory. We can explain this behavior by small chemical-potential oscillations and find a very good agreement between theory and experiment. A detailed wave-shape analysis of the dHvA signal corroborates the existence of an oscillating chemical potential.