Diagnosing Altermagnetic Phases through Quantum Oscillations

TL;DR

This paper demonstrates how quantum oscillation measurements can reveal the unique Fermi surface features of altermagnets, including spin-split orbits and Lifshitz transitions, providing a new diagnostic tool for these materials.

Contribution

It introduces a method to identify altermagnetic Fermi surfaces via quantum oscillations, highlighting the effects of Zeeman fields and spin-orbit coupling on their electronic properties.

Findings

Quantum oscillations reveal spin-split Fermi surfaces in altermagnets.

Lifshitz transitions cause frequency splitting and merging in quantum oscillation signals.

Zeeman fields induce distinct changes in cyclotron orbits and Landau levels.

Abstract

The recently delimited altermagnetic phase is characterized by zero net magnetization but momentum-dependent collinear spin-splitting. To explore the intriguing physical effects and potential applications of altermagnets, it is essential to analyze their Fermi surface properties, encompassing both configurations and spin textures. Here, we conduct a Fermiology study on metallic altermagnets and demonstrate that the collinear spin-split features of their Fermi surfaces can be clearly revealed through quantum oscillation measurements. By introducing a transverse Zeeman field to remove the spin-degenerate lines in the momentum space, the Fermi surface undergoes a Lifshitz transition, giving rise to spin-flipped cyclotron motion between orbits with opposite spins. Accordingly, the Lifshitz-Onsager quantization yields two sets of Landau levels, leading to frequency splitting of the Shubnikov-de Haas oscillations in conductivity. In the presence of spin-orbit coupling, the Zeeman field causes two separate cyclotron orbits to merge at the Lifshitz transition point before splitting again. This results in the two original frequencies discontinuously changing into a single frequency equal to their sum. Our work unveils a unique and universal signature of altermagnetic Fermi surfaces that can be probed through quantum oscillation measurements.