Observing Atomic Collapse Resonances in Artificial Nuclei on Graphene

Wang, Yan; Wong, Dillon; Shytov, A. V.; Brar, Victor W.; Choi, Sangkook; Wu, Qiong; Tsai, Hsin‐Zon; Regan, William; Zettl, A.; Kawakami, Roland; Louie, Steven G.; Levitov, L. S.; Crommie, Michael F.

doi:10.1126/science.1234320

Cited by 252 publications

(319 citation statements)

References 35 publications

(77 reference statements)

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“…The band gap can be controlled, e.g., in the case of carbon nanotubes, by applying an external field [48][49][50][51][52] or via strain [56] or, in graphene nanoribbons, by choosing certain nanoribbons with a desirable geometry [57]. Alternatively, the strength of the interaction potential can be controlled by having multiple charged impurities [58] or changing the dielectric environment.…”

Section: Discussionmentioning

confidence: 99%

One-dimensional Coulomb problem in Dirac materials

Downing

Portnoi

2014

Phys. Rev. A

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We investigate the one-dimensional Coulomb potential with application to a class of quasirelativistic systems, so-called Dirac-Weyl materials, described by matrix Hamiltonians. We obtain the exact solution of the shifted and truncated Coulomb problems, with the wave functions expressed in terms of special functions (namely, Whittaker functions), while the energy spectrum must be determined via solutions to transcendental equations. Most notably, there are critical band gaps below which certain low-lying quantum states are missing in a manifestation of atomic collapse.

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Section: Discussionmentioning

confidence: 99%

One-dimensional Coulomb problem in Dirac materials

Downing

Portnoi

2014

Phys. Rev. A

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“…Previously, the LDOS of graphene around clusters of pointlike charged impurities has been measured by scanning tunneling spectroscopy. 32 These experiments discovered peaks in LDOS, which were attributed to the emergence of the supercritical quasi-bound states. 33 We find that for a 1D perturbation the bound states, instead of the quasi-bound ones, produce the dominant features in the LDOS.…”

Section: Appendix B: Local Density and Density Of Statesmentioning

confidence: 99%

“…In graphene where the role of c is played by the Fermi velocity v F ∼ c/300, the critical charge is rather small, Z c ∼ 1 36,37 . This has made it possible to observe the long-sought supercriticality experimentally by measuring the tunneling density of states near charged impurities 32 . Analogous transitions 15 are possible for the bound states studied in this Letter, Fig.…”

Section: Appendix F: Supercritical Transitionsmentioning

confidence: 99%

Tunable Plasmonic Reflection by Bound 1D Electron States in a 2D Dirac Metal

Jiang

Pan

et al. 2016

Phys. Rev. Lett.

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We show that surface plasmons of a two-dimensional Dirac metal such as graphene can be reflected by line-like perturbations hosting one-dimensional electron states. The reflection originates from a strong enhancement of the local optical conductivity caused by optical transitions involving these bound states. We propose that the bound states can be systematically created, controlled, and liquidated by an ultranarrow electrostatic gate. Using infrared nanoimaging, we obtain experimental evidence for the locally enhanced conductivity of graphene induced by a carbon nanotube gate, which supports this theoretical concept.Plasmon scattering and plasmon losses in Dirac materials, such as graphene and topological insulators, are problems of interest to both fundamental and applied research. It is an outstanding challenge to understand various kinds of interaction (electron-electron, electron-phonon, electron-photon, electron-disorder) responsible for these complex phenomena [1][2][3][4][5] . At the same time, control of plasmon scattering is critical if this class of materials is to become a new platform for nanophotonics [6][7][8][9] .One source of plasmon scattering is long-range inhomogeneity of the electron density, which causes local fluctuations in the plasmon wavelength λ p . If the inhomogeneities are weak, those of size comparable to the average λ p are expected to be the dominant scatterers 10,11 Surprisingly, recent experiments have revealed that one-dimensional (1D) defects of nominally atomic width can act as effective reflectors for plasmons with wavelengths as large as a few hundred nm. Strong plasmon reflection was observed near grain boundaries 12,13 , topological stacking faults 14 , as well as nanometerscale wrinkles and cracks 11,12 in graphene. If this anomalous reflection is indeed an ubiquitous effect largely unrelated to the specific nature of a defect, it calls for a universal explanation. In this Letter we attribute its origin to electron bound states commonly occurring near 1D defects. We show that optical transitions involving the bound states can produce strong dissipation at small distances x from the defect and therefore, alter plasmon dynamics. To support this idea we present a theoretical analysis of an exactly solvable model, which illustrates qualitative and quantitative characteristics of the bound states and predicts how their optical response depends on the tunable parameters of a 1D potential well. We also report an attempt to probe the predicted effects experimentally. Our approach is to employ an ultranarrow electric gate in the form of a carbon nanotube (CNT) to create a precisely tunable 1D barrier in graphene. This device enables a systematic investigation and control of plasmon propagation, including, in principle, an implementation of a plasmon on-off switch (Fig. 1). What we find is that the measured real-space profile of the plasmon amplitude (Fig. 4) cannot be accounted for by a local change in λ p alone. Instead, the data are consistent with the presence of an enhanced ...

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“…Recently, Wang and his collaborators studied the graphene system with Coulomb impurities with STM and observed the resonance like the quasibound state [10]. They put Ca dimers as impurity, and measured the local density of states (LDOS) of electron around the impurity.…”

Section: Review On Coulomb Impurity On Graphenementioning

confidence: 99%

“…The massless fermion forms infinite number of quasibound states with negative energy, and the characteristic resonances appear in the local density of states (LDOS) of the electron [9]. Inspired by these theoretical studies, the scanning tunneling microscope (STM) experiment was carried out and a characteristic peak in LDOS was measured [10]. However, the above theoretical studies do not take into account the many body effect which involve electron-positron pair creation.…”

Section: Jhep02(2016)092mentioning

confidence: 99%

Bosonization approach for “atomic collapse” in graphene

Kagimura

Onogi

2016

J. High Energ. Phys.

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Abstract:We study quantum electrodynamics with 2+1 dimensional massless Dirac fermion around a Coulomb impurity. Around a large charge with atomic number Z > 137, the QED vacuum is expected to collapse due to the strong Coulombic force. While the relativistic quantum mechanics fails to make reliable predictions for the fate of the vacuum, the heavy ion collision experiment also does not give clear understanding of this system. Recently, the "atomic collapse" resonances were observed on graphene where an artificial nuclei can be made. In this paper, we present our nonperturbative study of the vacuum structure of the quasiparticles in graphene with a charge impurity which contains multi-body effect using bosonization method.

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Observing Atomic Collapse Resonances in Artificial Nuclei on Graphene

Cited by 252 publications

References 35 publications

One-dimensional Coulomb problem in Dirac materials

One-dimensional Coulomb problem in Dirac materials

Tunable Plasmonic Reflection by Bound 1D Electron States in a 2D Dirac Metal

Bosonization approach for “atomic collapse” in graphene

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