https://scholar.dgist.ac.kr/handle/20.500.11750/10043 Sat, 04 Apr 2026 15:17:15 GMT 2026-04-04T15:17:15Z https://scholar.dgist.ac.kr/handle/20.500.11750/59364 Title: Correlated Interlayer Quantum Hall State in Large-Angle Twisted Trilayer Graphene Author(s): Kim, Dohun; Lee, Gyeoul; Leconte, Nicolas; Jin, Seyoung; Taniguchi, Takashi; Watanabe, Kenji; Jung, Jeil; Cho, Gil Young; Kim, Youngwook Abstract: Trilayer graphene offers systematic control of its electronic structure through the stacking sequence and twist geometry, providing a versatile platform for correlated states. Here we report magnetotransport in a large-angle twisted trilayer graphene with a twist angle of about 5 degrees. The data reveal an electron-hole asymmetry that can be captured by introducing layer-dependent potential shifts. At charge neutrality (nu tot = 0), three low-resistance states appear, which Hartree-Fock mean-field analysis attributes to spin-resolved helical edge modes in the quantum Hall regime, analogous to quantum spin Hall-like configurations. At nu tot = -1, we also observe suppressed resistance when the middle and bottom layers are each half filled, while the top layer remains inert at nu = -2, consistent with an interlayer excitonic phase in the quantum Hall regime. These results demonstrate correlated interlayer quantum Hall phases in large-angle twisted trilayer graphene by combining spin-resolved helical edge transport with excitonic order. Wed, 31 Dec 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/59364 2025-12-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/58219 Title: Observation of 1/3 fractional quantum Hall physics in balanced large angle twisted bilayer graphene Author(s): Kim, Dohun; Jin, Seyoung; Taniguchi, Takashi; Watanabe, Kenji; Smet, Jurgen H.; Cho, Gil Young; Kim, Youngwook Abstract: Magnetotransport of conventional semiconductor based double layer systems with barrier suppressed interlayer tunneling has been a rewarding subject due to the emergence of an interlayer coherent state that behaves as an excitonic superfluid. Large angle twisted bilayer graphene offers unprecedented strong interlayer Coulomb interaction, since both layer thickness and layer spacing are of atomic scale and a barrier is no more needed as the twist induced momentum mismatch suppresses tunneling. The extra valley degree of freedom also adds richness. Here we report the observation of fractional quantum Hall physics at 1/3 total filling for balanced layer population in this system. Monte Carlo simulations support that the ground state is also an excitonic superfluid but the excitons are composed of fractional rather than elementary charges. The observed phase transitions with an applied displacement field at this and other fractional fillings are also addressed with simulations. They reveal ground states with different topology and symmetry properties. © The Author(s) 2024. Tue, 31 Dec 2024 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/58219 2024-12-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/57379 Title: Breaking barriers by interfacial charge transfer Author(s): Kim, Youngwook Abstract: The issue of ohmic contact in WSe2 has been effectively addressed through a significant charge transfer mechanism enabled by the RuCl3/WSe2 heterostructure. © Springer Nature Limited 2024. Sun, 30 Jun 2024 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/57379 2024-06-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/57374 Title: Non-Abelian fractional quantum anomalous Hall states and first Landau level physics of the second moiré band of twisted bilayer MoTe2 Author(s): Ahn, Cheong-Eung; Lee, Wonjun; Yananose, Kunihiro; Kim, Youngwook; Cho, Gil Young Abstract: Utilizing the realistic continuum description of twisted bilayer MoTe2 and many-body exact diagonalization calculation, we establish that the second moiré band of twisted bilayer MoTe2, at a small twist angle of approximately 2∘, serves as an optimal platform for achieving the long-sought non-Abelian fractional quantum anomalous Hall states without the need for external magnetic fields. Across a wide parameter range, our exact diagonalization calculations reveal that the half-filled second moiré band demonstrates the ground state degeneracy and spectral flows, which are consistent with the Pfaffian state in the first Landau level. We further elucidate that the emergence of the non-Abelian state is deeply connected to the remarkable similarity between the second moiré band and the first Landau level. Essentially, the band not only exhibits characteristics akin to the first Landau level, 12π∫BZd2ktrη(k)≈3 where ηab(k) is the Fubini-Study metric of the band, but also that its projected Coulomb interaction closely mirrors the Haldane pseudopotentials of the first Landau level. Motivated by this observation, we introduce a metric of first Landau level-ness of a band, which quantitatively measures the alignment of the projected Coulomb interaction with the Haldane pseudopotentials in Landau levels. This metric is then compared with the global phase diagram of the half-filled second moiré band, revealing its utility in predicting the parameter region of the non-Abelian state. In addition, we uncover that the first and third moiré bands closely resemble the lowest and second Landau levels, revealing a remarkable sequential equivalence between the moiré bands and Landau levels. We finally discuss the potential implications on experiments. © 2024 American Physical Society. Mon, 30 Sep 2024 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/57374 2024-09-30T15:00:00Z