When two layers of graphene are stacked with a twist angle of approximately 1.1°,strong interlayer coupling gives rise to a pair of flat bands in twisted bilayer graphene(TBG),resulting in pronounced electron–el...When two layers of graphene are stacked with a twist angle of approximately 1.1°,strong interlayer coupling gives rise to a pair of flat bands in twisted bilayer graphene(TBG),resulting in pronounced electron–electron interactions.At half filling of the flat bands,TBG exhibits correlated insulating states.Here,we investigate the electrical transport properties of heterostructures composed of TBG and the antiferromagnetic insulator chromium oxychloride(CrOCl),and propose a strategy to modulate the correlated insulating states in TBG.During the transition from a conventional phase to a strong interfacial coupling phase,kink-like features are observed in the charge neutrality point(CNP),correlated insulating state,and band insulating state.Under a perpendicular magnetic field,the system exhibits broadened quantum Hall plateaus in the strong interfacial coupling regime.Electrons localized in the CrOCl layer screen the bottom gate,rendering the carrier density in TBG less sensitive to variations in the bottom gate voltage.These phenomena are well captured by a charge-transfer model between TBG and CrOCl.Our results provide insights into the control of electronic correlations and topological states in graphene moirésystems via interfacial charge coupling.展开更多
With the packing density growing continuously in integrated electronic devices,sufficient heat dissipation becomes a serious challenge.Recently,dielectric materials with high thermal conductivity have brought insight ...With the packing density growing continuously in integrated electronic devices,sufficient heat dissipation becomes a serious challenge.Recently,dielectric materials with high thermal conductivity have brought insight into effective dissipation of waste heat in electronic devices to prevent them from overheating and guarantee the performance stability.Layered CrOCl,an antiferromagnetic insulator with low-symmetry crystal structure and atomic level flatness,might be a promising solution to the thermal challenge.Herein,we have systematically studied the thermal transport of suspended few-layer CrOCl flakes by microRaman thermometry.The CrOCl flakes exhibit high thermal conductivities along zigzag direction,from~392±33 to~1,017±46 W·m^(−1)·K^(−1) with flake thickness from 2 to 50 nm.Besides,pronounced thickness-dependent thermal conductivity ratio(/from~2.8±0.24 to~4.3±0.25)has been observed in the CrOCl flakes,attributed to the discrepancy of phonon dispersion and phonon surface scattering.As a demonstration to the heat sink application of layered CrOCl,we then investigate the energy dissipation in graphene devices on CrOCl,SiO_(2) and hexagonal boron nitride(h-BN)substrates,respectively.The graphene device temperature rise on CrOCl is only 15.4%of that on SiO_(2) and 30%on h-BN upon the same electric power density,indicating the efficient heat dissipation of graphene device on CrOCl.Our study provides new insights into two-dimentional(2D)dielectric material with high thermal conductivity and strong anisotropy for the application of thermal management in electronic devices.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52225207 and 52350001)the Shanghai Pilot Program for Basic Research–Fudan University 21TQ1400100(Grant No.21TQ006)the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)。
文摘When two layers of graphene are stacked with a twist angle of approximately 1.1°,strong interlayer coupling gives rise to a pair of flat bands in twisted bilayer graphene(TBG),resulting in pronounced electron–electron interactions.At half filling of the flat bands,TBG exhibits correlated insulating states.Here,we investigate the electrical transport properties of heterostructures composed of TBG and the antiferromagnetic insulator chromium oxychloride(CrOCl),and propose a strategy to modulate the correlated insulating states in TBG.During the transition from a conventional phase to a strong interfacial coupling phase,kink-like features are observed in the charge neutrality point(CNP),correlated insulating state,and band insulating state.Under a perpendicular magnetic field,the system exhibits broadened quantum Hall plateaus in the strong interfacial coupling regime.Electrons localized in the CrOCl layer screen the bottom gate,rendering the carrier density in TBG less sensitive to variations in the bottom gate voltage.These phenomena are well captured by a charge-transfer model between TBG and CrOCl.Our results provide insights into the control of electronic correlations and topological states in graphene moirésystems via interfacial charge coupling.
基金supported by the National Natural Science Foundation of China(No.11874423).
文摘With the packing density growing continuously in integrated electronic devices,sufficient heat dissipation becomes a serious challenge.Recently,dielectric materials with high thermal conductivity have brought insight into effective dissipation of waste heat in electronic devices to prevent them from overheating and guarantee the performance stability.Layered CrOCl,an antiferromagnetic insulator with low-symmetry crystal structure and atomic level flatness,might be a promising solution to the thermal challenge.Herein,we have systematically studied the thermal transport of suspended few-layer CrOCl flakes by microRaman thermometry.The CrOCl flakes exhibit high thermal conductivities along zigzag direction,from~392±33 to~1,017±46 W·m^(−1)·K^(−1) with flake thickness from 2 to 50 nm.Besides,pronounced thickness-dependent thermal conductivity ratio(/from~2.8±0.24 to~4.3±0.25)has been observed in the CrOCl flakes,attributed to the discrepancy of phonon dispersion and phonon surface scattering.As a demonstration to the heat sink application of layered CrOCl,we then investigate the energy dissipation in graphene devices on CrOCl,SiO_(2) and hexagonal boron nitride(h-BN)substrates,respectively.The graphene device temperature rise on CrOCl is only 15.4%of that on SiO_(2) and 30%on h-BN upon the same electric power density,indicating the efficient heat dissipation of graphene device on CrOCl.Our study provides new insights into two-dimentional(2D)dielectric material with high thermal conductivity and strong anisotropy for the application of thermal management in electronic devices.
