Topological and chiral quantum materials exhibit intriguing electronic, magnetic, and optical properties, holding great promise to shape future electronic and spintronic technologies. I will show three different approaches to manipulate quantum phases, based on physics models and density functional theory (DFT) calculations. First, exotic electronic band structures are realized through atomic lattice design, as exemplified by the design of perfectly flat bands based on the line graph theorem. I will present a system with two flat bands of opposite chirality that induces a giant circular dichroism effect. Secondly, topological states are manipulated by applying an external field. I will demonstrate a physical mechanism to remotely control the spin polarization of the topological corner states in a higher-order topological insulator. Thirdly, structural chirality engenders a chiral-induced spin selectivity effect, which enables the harnessing of electron spin to open promising opportunities in spintronics and quantum technologies. I will showcase the realization of higher-dimensional spin selectivity in chiral crystals for controlling phase transition and spin-flipping processes.
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