https://scholar.dgist.ac.kr/handle/20.500.11750/10043 2026-04-24T21:21:28Z https://scholar.dgist.ac.kr/handle/20.500.11750/60225 Title: Ferroelectric switching of interfacial dipoles in α-RuCl3/graphene heterostructure Author(s): Kim, Soyun; Yun, Jo Hyun; Choe, Junsik; Kim, Dohun; Taniguchi, Takashi; Watanabe, Kenji; Falson, Joseph; Kim, Jun Sung; Jin, Kyung-Hwan; Cho, Gil Young; Kim, Youngwook Abstract: We demonstrate electrically switchable, non-volatile dipoles in graphene/thin hBN/α-RuCl3 heterostructures, stabilized purely by interfacial charge transfer across an atomically thin dielectric barrier. This mechanism requires no sliding or twisting to explicitly break inversion symmetry and produces robust ferroelectric-like hysteresis loops that emerge prominently near 30 K. Systematic measurements under strong in-plane and out-of-plane magnetic fields reveal negligible effects on the hysteresis characteristics, confirming that the primary mechanism driving the dipole switching is electrostatic. Our findings establish a distinct and robust route to electrically tunable ferroelectric phenomena in van der Waals heterostructures, opening opportunities to explore the interplay between interfacial charge transfer and temperature-tuned barrier crossing of dipole states at the atomic scale. 2025-12-31T15:00:00Z 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. 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. 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. 2024-06-30T15:00:00Z