Modulating the Electronic Properties of Graphene by Self-Organized Sulfur Identical Nanoclusters and Atomic Superlattices Confined at an Interface

Ma, Donglin; Fu, Zhong-Qiu; Sui, Xuelei; Bai, Ke-Ke; Qiao, Jia-Bin; Yan, Chao; Zhang, Yu; Hu, Jingyi; Xiao, Qian; Mao, Xinrui; Duan, Wenhui; He, Lin

doi:10.1021/acsnano.8b04874

Cited by 21 publications

(21 citation statements)

References 67 publications

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“…Figures 1d and 1e show representative STS spectra recorded in two different regions of the 1.49º TBG and the doping in the two regions differs about 30 meV. The slight difference of the doping may arise from variations of the distance between Cu substrate and graphene owning to intercalation of S atoms that segregated from the Cu substrate, as demonstrated very recently 51,52 . The spectra shown in Figs.…”

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confidence: 78%

Spectroscopic Evidence for a Spin- and Valley-Polarized Metallic State in a Nonmagic-Angle Twisted Bilayer Graphene

et al. 2020

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In the magic-angle twisted bilayer graphene (MA-TBG), strong electron-electron (e-e) correlations caused by the band-flattening lead to many exotic quantum phases such as superconductivity, correlated insulator, ferromagnetism, and quantum anomalous Hall effects, when its low-energy van Hove singularities (VHSs) are partially filled. Here our high-resolution scanning tunneling microscope and spectroscopy measurements demonstrate that the e-e correlation in a non-magic-angle TBG with a twist angle θ = 1.49º still plays an important role in determining its electronic properties. Our most interesting observation on that sample is that when one of its VHS is partially filled, the one associated peak in the spectrum splits into four peaks. Our analysis based on the continuum model suggests that such a one-to-four split of the VHS originates from the formation of an interaction-driven spin-valley-polarized metallic state near the VHS, lifting both the spin and valley degeneracies. Our results for this non-magic-angle TBG reveal a new symmetry-breaking phase, which has not been identified in the MA-TBG or in other systems.

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confidence: 78%

Spectroscopic Evidence for a Spin- and Valley-Polarized Metallic State in a Nonmagic-Angle Twisted Bilayer Graphene

et al. 2020

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“…To obtain coupled graphene QDs, a new method is developed to generate circular pn junctions in a continuous graphene sheet. In our experiment, graphene monolayer was synthesized at high temperature by low pressure chemical vapor deposition (LPCVD) on a S-rich copper foil [31]. Then the sample is slowly cooled down to room temperature.…”

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confidence: 99%

Relativistic Artificial Molecules Realized by Two Coupled Graphene Quantum Dots

Pan

Zhou

et al. 2020

Nano Lett.

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Coupled quantum dots (QDs), usually referred to as artificial molecules, are important not only in exploring fundamental physics of coupled quantum objects, but also in realizing advanced QD devices. However, previous studies have been limited to artificial molecules with nonrelativistic fermions. Here, we show that relativistic artificial molecules can be realized when two circular graphene QDs are coupled to each other. Using scanning tunneling microscopy (STM) and spectroscopy (STS), we observe the formation of bonding and antibonding states of the relativistic artificial molecule and directly visualize these states of the two coupled graphene QDs. The formation of the relativistic molecular states strongly alters distributions of massless Dirac fermions confined in the graphene QDs. Because of the relativistic nature of the molecular states, our experiment demonstrates that the degeneracy of different angular-momentum states in the relativistic artificial molecule can be further lifted by external magnetic fields. Then, both the bonding and antibonding states are split into two peaks.

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“…In this work we show that atomically-resolved STM measurements are an ideal method for distinguishing between these competing states. The K-IVC can be detected by the formation of a √ 3 × √ 3 Kekulé pattern [18][19][20][21][22][23][24] only in the presence of a small (B ∼ 1 T) magnetic field, while other states can be detected via sublattice polarization and bond nematicity. Combined with transport measurements, the following states can be distinguished: 1) symmetric Dirac semimetal 2) nSM 3) K-IVC 4) Generic IVC state (e.g.…”

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Detecting symmetry breaking in magic angle graphene using scanning tunneling microscopy

Hong,

Soejima,

Zaletel

2021

Preprint

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A growing body of experimental work suggests that magic angle twisted bilayer graphene exhibits a "cascade" of spontaneous symmetry breaking transitions, sparking interest in the potential relationship between symmetry-breaking and superconductivity. However, it has proven difficult to find experimental probes which can unambiguously identify the nature of the symmetry breaking.Here we show how atomically-resolved scanning tunneling microscopy can be used as a fingerprint of symmetry breaking order. By analyzing the pattern of sublattice polarization and "Kekulé" distortions in small magnetic fields, order parameters for each of the most competitive symmetry-breaking states can be identified. In particular, we show that the "Kramers intervalley coherent state," which theoretical work predicts to be the ground state at even integer fillings, shows a Kekulé distortion which emerges only in a magnetic field.

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Modulating the Electronic Properties of Graphene by Self-Organized Sulfur Identical Nanoclusters and Atomic Superlattices Confined at an Interface

Cited by 21 publications

References 67 publications

Spectroscopic Evidence for a Spin- and Valley-Polarized Metallic State in a Nonmagic-Angle Twisted Bilayer Graphene

Spectroscopic Evidence for a Spin- and Valley-Polarized Metallic State in a Nonmagic-Angle Twisted Bilayer Graphene

Relativistic Artificial Molecules Realized by Two Coupled Graphene Quantum Dots

Detecting symmetry breaking in magic angle graphene using scanning tunneling microscopy

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