Novel Quantum Properties Arising from Symmetry Breaking in Topological Materials

Abstract

Recent advances in condensed matter physics have unveiled a new class of quantum materials known as topological insulators (TIs). TIs are insulating in the bulk while hosting metallic surface states within the bulk band gap. Notably, these surface states exhibit spin-polarized Dirac cones that are robust against backscattering, making TIs promising candidates for next-generation spintronic and quantum computing applications. Meanwhile, breaking a certain symmetry (e.g., inducing magnetism or ferroelectricity in TIs) gives rise to exotic quantum phenomena such as the quantum anomalous Hall effect, magnetic skyrmions, and Majorana fermions. These emergent phenomena are expected to offer new opportunities for fundamental physics and technological innovation.

In this talk, I will present recent research progress in topological materials based on my experimental work: magnetic topological insulator layered materials [1,2] (MnBi2Te4 and

MnSb2Te4) and ferroelectric topological insulators [3] (SnTe and PbSnSe) grown by molecular beam epitaxy. To probe the topological nature in terms of electronic structures, state-of-the-art angle-resolved photoemission spectroscopy (ARPES) is employed. Furthermore, low- temperature magnetotransport measurements are conducted to investigate quantum Hall effects and magnetic skyrmions reflecting the band topology. These research efforts provide new insights into the interplay of Dirac electrons and magnetic and crystalline structures, paving the way for future studies on quantum materials and their potential applications.

[1] E.D.L. Rienks, et al., Nature 576, 423 (2019).

[2] T. Takashiro, et al., Nano Letters 22, 881 (2022).

[3] G. Krizman, ..., T. Takashiro, et al., Phys. Rev. Lett. 132, 166601 (2024).

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