Phys.org October 30, 2023
Rhombohedral-stacked multilayer graphene hosts a pair of flat bands touching at zero energy, which should give rise to correlated electron phenomena that can be tuned further by an electric field. An international team of researchers (USA – MIT, Harvard University, Japan) measured electron transport through hexagonal boron nitride-encapsulated pentalayer graphene down to 100 mK and observed a correlated insulating state with resistance at the megaohm level or greater at charge density n = 0 and displacement field D = 0. By increasing D, they observed a Chern insulator state with C = −5 and two other states with C = −3 at a magnetic field of around 1 T. At high D and n, they observed isospin-polarized quarter- and half-metals. Hence, rhombohedral pentalayer graphene exhibited two different types of Fermi-surface instability, one driven by a pair of flat bands touching at zero energy, and one induced by the Stoner mechanism in a single flat band. According to the researchers their results rhombohedral multilayer graphene is a suitable system for exploring intertwined electron correlation and topology phenomena in natural graphitic materials without the need for moiré superlattice engineering… read more. TECHNICAL ARTICLE
Temperature and magnetic field dependence of the correlated insulator state. Credit: Nature Nanotechnology, 5 October 2023