Strong Coupling Superconductivity in Ca-Intercalated Bilayer Graphene on SiC

Wang, Xutao; Liu, Ningning; Wu, Yanfu; Qu, Yueqiao; Zhang, Wenxuan; Wang, Jinyue; Guan, Dandan; Wang, Shiyong; Zheng, Hao; Li, Yaoyi; Liu, Canhua; Jia, Jin‐Feng

doi:10.1021/acs.nanolett.2c02804

Cited by 10 publications

(15 citation statements)

References 55 publications

(84 reference statements)

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“…Inspired by the hydrogen intercalation at EG/SiC interface, many efforts have been made to intercalate metal atoms into the EG/SiC interface to form confined 2D metals. Most of the confined growths of 2D metals are achieved by intercalation under ultrahigh vacuum (UHV). − First, metal atoms are deposited on the buffer or EG surface via thermal or E-beam evaporation, sputtering, or MBE. Then metal/EG/SiC is annealed under vacuum and metal atoms will enter EG/SiC interface.…”

Section: Discussionmentioning

confidence: 99%

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Air-Stable, Large-Area 2D Metals and Semiconductors

Dong,

Lu,

Lin

et al. 2024

ACS Nanosci. Au

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materials are popular for fundamental physics study and technological applications in next-generation electronics, spintronics, and optoelectronic devices due to a wide range of intriguing physical and chemical properties. Recently, the family of 2D metals and 2D semiconductors has been expanding rapidly because they offer properties once unknown to us. One of the challenges to fully access their properties is poor stability in ambient conditions. In the first half of this Review, we briefly summarize common methods of preparing 2D metals and highlight some recent approaches for making air-stable 2D metals. Additionally, we introduce the physicochemical properties of some air-stable 2D metals recently explored. The second half discusses the air stability and oxidation mechanisms of 2D transition metal dichalcogenides and some elemental 2D semiconductors. Their air stability can be enhanced by optimizing growth temperature, substrates, and precursors during 2D material growth to improve material quality, which will be discussed. Other methods, including doping, postgrowth annealing, and encapsulation of insulators that can suppress defects and isolate the encapsulated samples from the ambient environment, will be reviewed.

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Section: Discussionmentioning

confidence: 99%

“…Copyright 2020 Springer Nature. (g, h) Superconducting properties of 2D Ca and Ga, respectively. , Adapted with permission from refs and . Copyright 2020 Springer Nature and 2022 American Chemical Society, respectively.…”

Section: Discussionmentioning

confidence: 99%

Air-Stable, Large-Area 2D Metals and Semiconductors

Dong,

Lu,

Lin

et al. 2024

ACS Nanosci. Au

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“…Superconductivity in ultra-thin two-dimensional (2D) films is of long-standing scientific importance and has undergone a recent revival of interest. Experimental studies of atomically thin elemental superconductors [1][2][3], superconducting 2D electron gases formed in layered oxide heterostructures [4,5], as well as 2D van-der-Waals materials such as transition metal dichalcogenides [6][7][8][9][10][11][12], FeSe [13][14][15][16][17], and various forms of multilayer graphene [18][19][20][21] have produced results that challenge the conventional understanding of superconductivity. Most recently, the ability to tune properties by gate voltages and novel heterostructuring including 'moiré' systems [22][23][24][25][26][27][28] has further increased the interest in 2D superconductivity and rendered layered superconductors a promising platform for many-body material design.…”

Section: Introductionmentioning

confidence: 99%

Screening induced crossover between phonon- and plasmon-mediated pairing in layered superconductors

in’t Veld,

Katsnelson,

Millis

et al. 2023

2D Mater.

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Two-dimensional (2D) metals can host gapless plasmonic excitations that strongly couple to electrons and thus may significantly affect superconductivity. To investigate the dynamical interplay of the electron–electron and electron–phonon interactions in the theory of 2D superconductivity, we apply a full momentum- and frequency-dependent one-loop theory treating electron–phonon, electron–plasmon, and phonon–plasmon coupling with the same accuracy. We tune the strength of the Coulomb interaction by varying the external screening ε e x t to the layered superconductor and find three distinct regions. At weak screening, superconductivity is mediated by plasmons. In the opposite limit conventional electron–phonon interactions dominate. In between, we find a suppressed superconducting state. Our results show that even in conventional electron–phonon coupled layered materials, superconductivity can be significantly enhanced by the electron–plasmon coupling in a manner that can be controlled by the external screening.

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“…Recently, graphene intercalation has attracted considerable attention owing to the functionalization of graphene during the intercalation process. − Intercalation by various metals can customize Dirac Fermions, triggering unique quantum phenomena within graphene. For instance, metal atomic intercalation can generate a bandgap with massive Dirac Fermions in graphene. − Furthermore, Ca-intercalation can typically induce charge density waves (CDWs) and two-dimensional (2D) superconductivity within epitaxial bilayer graphene on SiC. − In addition, Briggs et al documented the observation of 2D superconductivity at the graphene/SiC heterointerface via Ga intercalation, featuring a critical superconducting temperature of 3.2 K . The Kekulé-ordered state has been reported within Li-intercalated graphene possessing a (√3 × √3)R30° superlattice, where the chiral symmetry was broken. − The Lifshitz transition beyond the van Hove singularity has been achieved in overdoped epitaxial graphene through Yb intercalation and potassium adsorption .…”

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confidence: 99%

Observation of a Folded Dirac Cone in Heavily Doped Graphene

Wang

et al. 2023

J. Phys. Chem. Lett.

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Superlattice potentials imposed on graphene can alter its Dirac states, enabling the realization of various quantum phases. We report the experimental observation of a replica Dirac cone at the Brillouin zone center induced by a superlattice in heavily doped graphene with Gd intercalation using angle-resolved photoemission spectroscopy (ARPES). The replica Dirac cone arises from the (√3× √3)R30°superlattice formed by the intervalley coupling of two nonequivalent valleys (e.g., the Kekule-like distortion phase), accompanied by a bandgap opening. According to the findings, the replica Dirac band in Gd-intercalated graphene disappears beyond a critical temperature of 30 K and can be suppressed by potassium adsorption. The modulation of the replica Dirac band is primarily attributable to the residual frozen gas, which can act as a source of intervalley scattering at temperatures below 30 K. Our results highlight the persistence of the hidden Kekule-like phase within the heavily doped graphene, enriching our current understanding of its replica Dirac Fermions.

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Strong Coupling Superconductivity in Ca-Intercalated Bilayer Graphene on SiC

Cited by 10 publications

References 55 publications

Air-Stable, Large-Area 2D Metals and Semiconductors

Air-Stable, Large-Area 2D Metals and Semiconductors

Screening induced crossover between phonon- and plasmon-mediated pairing in layered superconductors

Observation of a Folded Dirac Cone in Heavily Doped Graphene

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