Title : Replica topology of a quantum fractal
일시 : 2022년 12월 9일 (금) 16시, 아산이학관 440A호
Speaker : 김영국 교수 (성균관대학교 물리학과)
Replica topology of a quantum fractal
Youngkuk Kim1
1Department
of Physics, Sungkyunkwan University, Suwon, Korea
Hofstadter
butterflies, a quantum fractal spectrum of electrons in a strong magnetic
field, have fascinated researchers across various disciplines. Here we report
the scientific discovery and major computational breakthrough that
self-similarity-driven topological phases arise in Hofstadter butterflies by
rigorous demonstration of a large-scale simulation of twisted bilayer graphene.
Without any protection of underlying symmetries, Hofstadter butterflies realize
a topological phase as replicas of the original topology. This is particularly
remarkable when considering the standard phenomenology of symmetry-protected
topological phases. The self-similarity copies the energy spectrum and the
underlying topological structures. We demonstrate this by performing
large-scale numerical calculations in twisted bilayer graphene using Kernel
polynomial methods for the first time for the calculations of the Hofstadter
butterflies in a realistic atomic model, which leads to the beautiful
high-resolution quantum fractal shown in the figure below.
Figure: Hofstadter butterflies of
twisted bilayer graphene