Abstract
The interactions among the macroscopic number of electrons in crystalline solids can lead to the emergence of new states of matter that cannot be described by the properties of the individual constituents. Quantum materials, in which ‘emergent’ phenomena are manifest, have become a recent focus of condensed matter research. In this talk, I will review recent experimental discoveries of anomalous metallic behaviour in materials on the brink of metal-insulator transitions, probed via high magnetic fields created in a highly controlled environment. In SmB6, an archetypal Kondo insulator with 4f electrons, the observation of magnetic quantum oscillations indicates the existence of a coherent Fermi surface within its insulating bulk [1], challenging the established distinction between a metallic and insulating state within the Landau-Fermi liquid paradigm. In the cuprate superconductor YBa2Cu3O6+x with a Mott-insulating parent state, definite signatures of a Fermi surface and superconductivity are found to coexist in the underdoped regime [2],
contrasting the strange metallic states with T-linear resistivity and H-linear agnetoresistance in the overdoped side [3]. Lastly, I will present new results of magnetotransport studies on infinite-layer nickelates, which reveal the anomalous metallic behaviour in this new model system for unconventional superconductivity [4]. These results highlight the approach of exposing materials near metal-insulator transitions to high magnetic fields as a promising avenue for discoveries in quantum solids.