First Observation of Quantum Oscillations in the Ferromagnetic Superconductor UCoGe

TL;DR

This study reports the first observation of quantum oscillations in the ferromagnetic superconductor UCoGe, revealing a small, heavy Fermi surface that changes with magnetic field, advancing understanding of its electronic structure.

Contribution

First detection of Shubnikov-de Haas oscillations in UCoGe, providing new insights into its Fermi surface and quasiparticle properties.

Findings

Detected a small Fermi surface pocket with heavy effective mass

Fermi surface volume decreases nonlinearly with increasing magnetic field

Cyclotron mass decreases along with resistivity coefficient A

Abstract

We succeeded in growing high quality single crystals of the ferromagnetic superconductor UCoGe and measured the magnetoresistance at fields up to 34T. The Shubnikov-de Haas signal was observed for the first time in a U-111 system (UTGe, UTSi, T: transition metal). A small pocket Fermi surface (F~1kT) with large cyclotron effective mass 25m0 was detected at high fields above 22T, implying that UCoGe is a low carrier system accompanyed with heavy quasi-particles. The observed frequency decreases with increasing fields, indicating that the volume of detected Fermi surface changes nonlinearly with field. The cyclotron mass also decreases, which is consistent with the decrease of the A coefficient of resistivity.