Lifshitz Transitions in the Ferromagnetic Superconductor UCoGe

TL;DR

This study investigates how high magnetic fields induce multiple Fermi surface instabilities in the ferromagnetic superconductor UCoGe, revealing complex electronic structure changes through various measurements.

Contribution

It provides the first detailed experimental evidence of Lifshitz transitions in UCoGe under high magnetic fields using multiple probes.

Findings

Five successive anomalies observed at specific magnetic fields.

Detection of magnetic quantum oscillations in resistivity and thermopower.

Significant changes in oscillation frequencies and effective masses indicating Fermi surface instabilities.

Abstract

We present high field magnetoresistance, Hall effect and thermopower measurements in the Ising-type ferromagnetic superconductor UCoGe. Magnetic field is applied along the easy magnetization $c$ axis of the orthorhombic crystal. In the different experimental probes we observed five successive anomalies at $H \approx 4$, 9, 12, 16, and 21~T. Magnetic quantum oscillations were detected both in resistivity and thermoelectric power. At most of the anomalies, significant changes of the oscillation frequencies and the effective masses have been observed indicating successive Fermi surface instabilities induced by the strong magnetic polarization under magnetic field.