Applied Physics Seminar | Metal or insulator? That is the question

Abstract:
Lu will talk about the dual nature of the topological Kondo insulators. They are perfect insulators like pure silicon, and their electrical resistivity diverges by more than a million times during cooling down. Yet, they show a characteristic feature of good metal---oscillations in magnetization under magnetic fields.

In this talk, Lu will review his discovery of this contradiction: his quest to observe insulators’ oscillations, not only in magnetization but also in electrical resistivity. His experiments demonstrate that the oscillatory carriers are just like electrons, following the Fermi-Dirac distributions, even in this perfect insulator. So, can the compound be both metal and insulator? Or can a fermion exist in solids even without electrical charge? Let's find the answer.

References:
[1] Xiang, Z. et al., Science 362, 65 (2018).
[2] Li, Lu et al., Nature Review Physics 2, 463 (2020).
[3] Xiang, Z., et al., Nature Physics 17, 788 (2021).
[4] Zheng, G. et al., PNAS 122, e2421390122 (2025)
[5] Li, G. et al., Science 346, 1208 (2014).
[6] Xiang, Z., et al., Physical Review X 7, 031054 (2017).
[7] Chen, KW, et al., Physical Review Letters 135, 156501 (2025).
[8] Zheng, G. et al., Physical Review X 15, 021076 (2025).