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Topology and Transport in Chiral Magnetoelectric Nanomaterials under Extreme Conditions


The goal of this proposal is to investigate, theoretically, numerically, and experimentally, the connection between electronic transport and topology in 1D, 2D, and 3D chiral nanomaterialsunder extreme conditions. This project will be executed by the visiting researcher to the group of Prof. Dr. Rodrigo Capaz, director of LNNANO/CNPEM. We are going to study semiconductingmaterials with a correlated gap that can be driven into a metallic state by the tuning of externalparameters. When such metallic phase happens to occur close to a ferromagnetic or ferroelectricordering the role of topology will become evident by the different possibilities for the Berry curvature; the magnetism breaks time reversal symmetry while polarizability breaks space inversion symmetry, chirality, leaving signatures in transport to be compared to the ongoing experiments.The theoretical methods include Mott's theory for the transport properties in metals anddoped semiconductors at low temperatures, quantum corrections to conductivity in disorderedsystems and under hydrostatic pressure, the quantum kinetic equations in the presence of external electric and magnetic fields, the k.p method for Bloch states in electronic bands withnonzero Berry curvature and the many body Green's functions for strongly correlated systems. Some of the phenomena to be investigated include thermoelectricity, electrical conductivity, Hallresponse, Nernst effect, Kerr effect, Pockels effect, all of which under extreme conditions of temperature, pressure, and disorder. Special attention will be given to tellurium, in all its allotropic forms, as well as to other tellurium based compounds. The reason is tellurium peculiar chiral structure. Gyrotropy in tellurium, combined to inhomogeneities at the nanoscale produce veryinteresting phenomena in tellurium, generating the simultaneous breakdown of both time reversal and space inversion symmetries, which renders tellurium a novel paradigm for the study ofthe transport properties in topological systems.It is worth emphasizing the reaching potential of this proposal, that includes several other institutions in the state of São Paulo, such as Unicamp, USP, ILUM, LNLS and LNNANO. From thetechnological point of view, completing the research project at LNNANO/CNPEM will allow thedesign, fabrication, and characterization of prototypes for technological devices at the nanoscale with possible applications to optical, magnetic, and thermelectric sensors, efficient storage devices for sustainable energy and also of topological nanodiodes and nanotransistors. (AU)

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