Subhajit Roychowdhury

Humboldt Fellow as of August 2021

Overview of my Research Project:

Crystal symmetry and magnetism are the two important tools to tailor material properties, especially in topological materials. Magnetic topological insulators (MTIs) are mainly narrow band gap semiconductor which combine magnetic order and non-trivial band topology together. Thus, it is necessary to understand how topological properties are affected by structural imperfections, such as the presence of atoms with a nonzero magnetic moment to make practical devices based on TIs. In contrast to their nonmagnetic counterparts, MTIs have some of the surfaces gapped which allow for a variety of exotic phenomena with potential applications in spintronics such as the quantum anomalous Hall effect (QAHE), topological axion insulating states, Majorana modes etc. So far, magnetic topological insulators have only been created by means of doping nonmagnetic topological insulators with 3d ferromagnets. However, the fabrication, measurement, and property optimization of those devices are quite challenging, restricting the observation of important phenomena to low temperatures or high magnetic field which limit the use of these materials for practical applications. Hence, searching for intrinsic and stoichiometric MTIs with less rigid constraints are urgently needed to realize exotic quantum phenomenon experimentally. In this scenario, intrinsic antiferromagnetic (AFM) topological insulators (TIs) with a 2-invariant, offer a fertile ground for the exploration of such exotic quantum phenomena. However, the research on AFM TIs is still in its infancy.

As an awardee of prestigious Alexander von Humboldt fellowship, my research work is focused on the investigations of magnetic and transport properties of antiferromagnetic topological insulators. Synthesizing novel intrinsic magnetic topological materials in which magnetism and topology natively coexist, becomes a key research topic to future applications. Further, more experimental, and systematic research on antiferromagnetic topological insulators is required to discover novel fundamental physics as well as making new quantum devices. The materials will be synthesized in the single crystalline form followed by thin flakes devices. Temperature and magnetic field dependent electrical and thermal transport property measurement will be performed in Prof. Claudia Felser group at the Max Planck Institute for Chemical Physics of Solids in Dresden. Her group is an outstanding combination of synthesis, characterizations, measurements of inorganic solids and understanding of the electronic structures via theoretical calculations. Moreover, the group’s excellent scientific expertise in solid-state chemistry and physics offers a sound basis for executing my proposed research project.

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