Spin-orbit interaction(SOI)can be introduced by the proximity effect to modulate the electronic properties of graphene-based heterostructures.In this work,we stack trilayer WSe_(2) on Bernal tetralayer graphene to inv...Spin-orbit interaction(SOI)can be introduced by the proximity effect to modulate the electronic properties of graphene-based heterostructures.In this work,we stack trilayer WSe_(2) on Bernal tetralayer graphene to investigate the influence of SOI on the anomalous Hall effect(AHE).In this structurally asymmetric device,by comparing the magnitude of AHE at positive and negative displacement fields,we find that AHE is strongly enhanced by bringing electrons in proximity to the WSe_(2) layer.Meanwhile,the enhanced AHE signal persists up to 80 K,providing important routes for topological device applications at high temperatures.展开更多
Recent experimental findings have demonstrated the occurrence of superconductivity in Bernal bilayer graphene when induced by a magnetic field.In this study,we conduct a theoretical investigation of the potential pair...Recent experimental findings have demonstrated the occurrence of superconductivity in Bernal bilayer graphene when induced by a magnetic field.In this study,we conduct a theoretical investigation of the potential pairing symmetry within this superconducting system.By developing a theoretical model,we primarily calculate the free energy of the system with p+ip-wave parallel spin pairing,p+ip-wave anti-parallel spin pairing and d+i d-wave pairing symmetry.Our results confirm that the magnetic field is indeed essential for generating the superconductivity.We discover that the p+ip-wave parallel spin pairing leads to a lower free energy for the system.The numerical calculations of the energy band structure,zero-energy spectral function and density of states for each of the three pairing symmetries under consideration show a strong consistency with the free energy results.展开更多
We consider the AB-(Bernal) stacking for the bi-layer graphene (BLG) system and assume that a perpendicular electric field is created by the external gates deposited on the BLG surface. In the basis (A1, B2, A2, B1) f...We consider the AB-(Bernal) stacking for the bi-layer graphene (BLG) system and assume that a perpendicular electric field is created by the external gates deposited on the BLG surface. In the basis (A1, B2, A2, B1) for the valleyKand the basis (B2, A1, B1, A2) for the valley K′, we show the occurrence of trigonal warping [1], that is, splitting of the energy bands or the density of states on the kx - ky plane into four pockets comprising of the central part and three legs due to a (skew) interlayer hopping between A1 and B2. The hopping between A1 - B2 leads to a concurrent velocity v3 in addition to the Fermi velocity vF. Our noteworthy outcome is that the above-mentioned topological change, referred to as the Lifshitz transition [2, 3], is entirely bias-tunable. Furthermore, the many-body effects, which is known to yield logarithmic renormalizations [4] in the band dispersions of monolayer graphene, is found to have significant effect on the bias-tunability of this transition. We also consider a variant of the system where the A atoms of the two layers are over each other and the B atoms of the layers are displaced with respect to each other. The Fermi energy density of statesfor zero bias corresponds to the inverted sombrero-like structure. The structure is found to get deformed due to the increase in the bias.展开更多
Tetralayer graphene has shown several interesting properties such as tunable Lifshitz transitions,helical edge states,and high-temperature anomalous Hall effects.The band structure,which directly relates to these phen...Tetralayer graphene has shown several interesting properties such as tunable Lifshitz transitions,helical edge states,and high-temperature anomalous Hall effects.The band structure,which directly relates to these phenomena,has so far been predominantly determined by fitting Landau-level spectra.Here,by characterizing the electronic capacitance,we reveal unprecedented details of its band structure:the energy shift between the heavy-and light-mass band edges in the conduction band is much larger than that in the valence band.Their responses to displacement fields are also distinct:while the former increases monotonically and significantly,the latter first decreases and then increases slightly.Our results suggest that the interlayer interactions and hopping parameters are more complex than previously expected,calling for precise measurements of band structures in various multilayer van der Waals systems.展开更多
Graphene, defined as a single atomic plane of graphite, is a semimetal with a small overlap between the valence and conduction bands. The stacking of graphene up to several atomic layers can lead to diverse physical p...Graphene, defined as a single atomic plane of graphite, is a semimetal with a small overlap between the valence and conduction bands. The stacking of graphene up to several atomic layers can lead to diverse physical properties, depending on the stacking method. Bi layer graphene is also a semimetal, adopting the AB-stacked (or Bernal-stacked) structure or the rare AA-stacked structure . Trilayer or few-layer graphene (FLG) can be semimetals or semiconductors, depending on whether they adopt Bernal (ABA) stacking or rhoinbohedral (ABC) stacking.展开更多
The remarkable properties of graphene have shown promise for new perspectives in future electronics, notably for nanometer scale devices. Here we grow graphene epitaxially on an off-axis 4H-SiC（0001） substrate and d...The remarkable properties of graphene have shown promise for new perspectives in future electronics, notably for nanometer scale devices. Here we grow graphene epitaxially on an off-axis 4H-SiC（0001） substrate and demonstrate the formation of periodic arrangement of monolayer graphene on planar （0001） terraces and Bernal bilayer graphene on （1120） nanofacets of SiC. We investigate these lateral superlattices using Raman spectroscopy, atomic force microscopy/ electrostatic force microscopy （AFM/EFM） and X-ray and angle resolved photoemission spectroscopy （XPS/ARPES）. The correlation of EFM and ARPES reveals the appearance of permanent electronic band gaps in AB-stacked bilayer graphene on （1120） SiC nanofacets of 150 meV. This feature is confirmed by density functional theory （DFT） calculations. The charge transfer between the substrate and graphene bilayer results in an asymmetric charge distribution between the top and the bottom graphene layers opening an energy gap. This surface organization can be thus defined as self-organized metal-semiconductor graphene.展开更多
基金Project supported by the National Key R&D Program of China(Grant Nos.2021YFA1400100 and 2024YFA1409700)the National Natural Science Foudation of China(Grant Nos.12374168 and T2325026)。
文摘Spin-orbit interaction(SOI)can be introduced by the proximity effect to modulate the electronic properties of graphene-based heterostructures.In this work,we stack trilayer WSe_(2) on Bernal tetralayer graphene to investigate the influence of SOI on the anomalous Hall effect(AHE).In this structurally asymmetric device,by comparing the magnitude of AHE at positive and negative displacement fields,we find that AHE is strongly enhanced by bringing electrons in proximity to the WSe_(2) layer.Meanwhile,the enhanced AHE signal persists up to 80 K,providing important routes for topological device applications at high temperatures.
基金Project supported by the National Natural Science Foundation of China (Grant No.12074130)the Natural Science Foundation of Guangdong Province (Grant No.2021A1515012340)。
文摘Recent experimental findings have demonstrated the occurrence of superconductivity in Bernal bilayer graphene when induced by a magnetic field.In this study,we conduct a theoretical investigation of the potential pairing symmetry within this superconducting system.By developing a theoretical model,we primarily calculate the free energy of the system with p+ip-wave parallel spin pairing,p+ip-wave anti-parallel spin pairing and d+i d-wave pairing symmetry.Our results confirm that the magnetic field is indeed essential for generating the superconductivity.We discover that the p+ip-wave parallel spin pairing leads to a lower free energy for the system.The numerical calculations of the energy band structure,zero-energy spectral function and density of states for each of the three pairing symmetries under consideration show a strong consistency with the free energy results.
文摘We consider the AB-(Bernal) stacking for the bi-layer graphene (BLG) system and assume that a perpendicular electric field is created by the external gates deposited on the BLG surface. In the basis (A1, B2, A2, B1) for the valleyKand the basis (B2, A1, B1, A2) for the valley K′, we show the occurrence of trigonal warping [1], that is, splitting of the energy bands or the density of states on the kx - ky plane into four pockets comprising of the central part and three legs due to a (skew) interlayer hopping between A1 and B2. The hopping between A1 - B2 leads to a concurrent velocity v3 in addition to the Fermi velocity vF. Our noteworthy outcome is that the above-mentioned topological change, referred to as the Lifshitz transition [2, 3], is entirely bias-tunable. Furthermore, the many-body effects, which is known to yield logarithmic renormalizations [4] in the band dispersions of monolayer graphene, is found to have significant effect on the bias-tunability of this transition. We also consider a variant of the system where the A atoms of the two layers are over each other and the B atoms of the layers are displaced with respect to each other. The Fermi energy density of statesfor zero bias corresponds to the inverted sombrero-like structure. The structure is found to get deformed due to the increase in the bias.
基金supported by the National Natural Science Foundation of China(Grant Nos.123B1037 and 12274402)the National Key Research and Development Program of China(Grant No.2024YFA1409700).
文摘Tetralayer graphene has shown several interesting properties such as tunable Lifshitz transitions,helical edge states,and high-temperature anomalous Hall effects.The band structure,which directly relates to these phenomena,has so far been predominantly determined by fitting Landau-level spectra.Here,by characterizing the electronic capacitance,we reveal unprecedented details of its band structure:the energy shift between the heavy-and light-mass band edges in the conduction band is much larger than that in the valence band.Their responses to displacement fields are also distinct:while the former increases monotonically and significantly,the latter first decreases and then increases slightly.Our results suggest that the interlayer interactions and hopping parameters are more complex than previously expected,calling for precise measurements of band structures in various multilayer van der Waals systems.
文摘Graphene, defined as a single atomic plane of graphite, is a semimetal with a small overlap between the valence and conduction bands. The stacking of graphene up to several atomic layers can lead to diverse physical properties, depending on the stacking method. Bi layer graphene is also a semimetal, adopting the AB-stacked (or Bernal-stacked) structure or the rare AA-stacked structure . Trilayer or few-layer graphene (FLG) can be semimetals or semiconductors, depending on whether they adopt Bernal (ABA) stacking or rhoinbohedral (ABC) stacking.
文摘The remarkable properties of graphene have shown promise for new perspectives in future electronics, notably for nanometer scale devices. Here we grow graphene epitaxially on an off-axis 4H-SiC（0001） substrate and demonstrate the formation of periodic arrangement of monolayer graphene on planar （0001） terraces and Bernal bilayer graphene on （1120） nanofacets of SiC. We investigate these lateral superlattices using Raman spectroscopy, atomic force microscopy/ electrostatic force microscopy （AFM/EFM） and X-ray and angle resolved photoemission spectroscopy （XPS/ARPES）. The correlation of EFM and ARPES reveals the appearance of permanent electronic band gaps in AB-stacked bilayer graphene on （1120） SiC nanofacets of 150 meV. This feature is confirmed by density functional theory （DFT） calculations. The charge transfer between the substrate and graphene bilayer results in an asymmetric charge distribution between the top and the bottom graphene layers opening an energy gap. This surface organization can be thus defined as self-organized metal-semiconductor graphene.
