In metals or semimetals, the application of a strong magnetic field at low temperature leads to the quantization of electronic states into discrete Landau levels with distinct energies, resulting in periodic oscillations of the density of states near the Fermi surface, dubbed quantum oscillations.
These oscillations were experimentally observed in magnetization and resistivity measurements performed in bismuth during the 1930s and are known as de Haas–van Alphen (dHvA) and Shubnikov–de Haas (SdH) effects, respectively. The oscillations period is traditionally represented in an inverse magnetic field plot. The corresponding frequency (Fr) is proportional to the extremal cross-section of the Fermi surface (AF) perpendicular to the applied field, as dictated by the Onsager relation Fr = (φ0/2π2)AF, where φ0 = h/2e is the magnetic flux quantum. This characteristic establishes quantum oscillations as one of the most powerful tools for investigating the geometry of Fermi surface. In parallel, the temperature evolution of the amplitude of quantum oscillations is directly linked to the effective mass of the electronic carriers, which is the footprint of the degree of correlations in the material. Quantum oscillations appear as the main way to experimentally determine the band structure of a material, as its DNA, and compare it with different theoretical prediction.
Typically, the magnitude of the quantum oscillations at a specific frequency increase with decreasing temperature and increasing magnetic field. Consequently, a comprehensive information about the Fermi surface is obtained through measurements of quantum oscillations under extreme conditions of ultralow temperatures (<1 K) and high magnetic fields (>20 T). Our strategy in the team is to develop several probes to detect these oscillations in different quantum materials: resistivity, magnetization, thermoelectricity and recently tunnel diode measurements. In collaboration with the high magnetic field laboratory LNCMI of the CNRS in Grenoble, we were able to not only map the detailed fermiology of different materials but also to detect specific changes of the topology of the Fermi surface called Lifshitz transitions. Lifshitz transitions recently attracted a renewed interest in the possible role they have in various transitions between competing orders in quantum materials, as metamagnetic or superconducting transitions.
Z. Yang, et al.
Unveiling the double-peak structure of quantum oscillations in the specific heat
Nat. Commun 14, 7006 (2023)
G. Bastien et al.
Lifshitz Transitions in the Ferro-magnetic Superconductor UCoGe
Phys. Rev. Lett. 117, 206401 (2016)
A. Palacio-Morales et al.
Thermoelectric power quantum oscillations in the ferromagnet UGe2
Phys. Rev. B 93, 155120 (2016)