Exploring the Interplay of MAGnetism and electronic properties in monolayers of magnetic topological INsulators

• Applicants: Alexey Alfonsov, Ph.D.; Joseph Dufouleur, Ph.D.
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545611182

Quantum materials display a broad range of collective phenomena governed by quantum mechanics and hold great promise for future applications. In 2D materials in particular, topological phases such as the Quantum Anomalous Hall (QAH) effect hold promises for potential application in the field of spintronics, quantum metrology, or low-power electronics. The quantum anomalous Hall effect (QAH), characterised by a one-dimensional edge channel circulating around an insulating surface at zero magnetic field, has been first observed in magnetically-doped 3D topological insulators (TI) nearly a decade ago, it has been extremely difficult to reproduce and control. A new paradigm recently developed with the discovery of intrinsically magnetic TI such as MnBi2Te4 (MBT). In magnetic TIs, time reversal symmetry is broken in the whole bulk without affecting the topological character, resulting in the opening of a magnetic gap in surface states. The MBT family and other magnetic TIs are currently intensively investigated in growth, spectroscopy and transport, to understand their electronic and topological properties. In particular, electronic, topological and magnetic properties are strongly coupled with each other and are related to the microscopic disorder of the system. This project aims at investigating the interplay between magnetism, electronic properties and topology in bulk to monolayers of MBT, through magnetotransport measurements and electrically-detected electron spin resonance (ED-ESR) experiments. To this end, we will study quantum transport in nanostructures of high-quality epitaxial MBT thin films in up to very high magnetic field as well as the spin dynamics of the system through ED-ESR. In particular, we will investigate heterostructures of MBT monolayers on Bi2Te3 (monoMBT/BT) who are predicted to realize a new ferromagnetic QAH system. The project is oriented along two main axes: 1. The investigation of the electronic properties (effective mass, band bending) of thin films of MBT down to monolayer thickness through quantum oscillations (Shubnikov-de-Haas oscillations) in high magnetic fields. 2. The investigation of static and dynamical spin and electronic properties in thin films and monolayers of magnetic topological insulators MBT through quantum transport and ED-ESR. To access information about the magnetic disorder, quantum interferences (universal conductance fluctuations, Aharonov-Bohm effect) will be measured down to very low temperature. Furthermore, the dynamic of the spins and their interaction with conduction electrons (trivial and topological) will be investigated through ED-ESR.

• DFG Programme: Research Grants
• International Connection: France
• Partner Organisation: Agence Nationale de la Recherche / The French National Research Agency
• Cooperation Partner: Professor Dr. Louis Veyrat