Position and momentum mapping of vibrations in graphene nanostructures

Senga, Ryosuke; Suenaga, Kazu; Barone, Paolo; Morishita, Shigeyuki; Mauri, Francesco; Pichler, Thomas

doi:10.1038/s41586-019-1477-8

Cited by 127 publications

(130 citation statements)

References 23 publications

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“…Following Ref. (24), we assign these peaks to scattering by transverse (T) and longitudinal (L), acoustic (A) or optical (O) modes in graphene, respectively (the graphene phonon dispersion diagram is presented for 35 reference in fig. S10).…”

Section: Main Textmentioning

confidence: 99%

Single-atom vibrational spectroscopy in the scanning transmission electron microscope

Hage

Radtke

Kepaptsoglou

et al. 2020

Science

196

158

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Single-atom impurities and other atomic-scale defects can notably alter the local vibrational responses of solids and, ultimately, their macroscopic properties. Using high-resolution electron energy-loss spectroscopy in the electron microscope, we show that a single substitutional silicon impurity in graphene induces a characteristic, localized modification of the vibrational response. Extensive ab initio calculations reveal that the measured spectroscopic signature arises from defect-induced pseudo-localized phonon modes—that is, resonant states resulting from the hybridization of the defect modes and the bulk continuum—with energies that can be directly matched to the experiments. This finding realizes the promise of vibrational spectroscopy in the electron microscope with single-atom sensitivity and has broad implications across the fields of physics, chemistry, and materials science.

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Section: Main Textmentioning

confidence: 99%

Single-atom vibrational spectroscopy in the scanning transmission electron microscope

Hage

Radtke

Kepaptsoglou

et al. 2020

Science

196

158

View full text Add to dashboard Cite

show abstract

“…Of course, INS studies of single-layer materials seem to be impossible due to a small number of atoms. However, other techniques such as electron energy loss spectroscopy can be, in principle, used 61 . Our work suggests the necessity of an explicit treatment of electron correlations to accurately describe the magnetism in the broad family of layered magnetic materials 62,63 , including magnetic topological vdW materials 64,65 , where the interaction between magnetization and the topological surface state is essential.…”

Section: Stacking-dependent Magnetic Orderingmentioning

confidence: 99%

Electron correlation effects on exchange interactions and spin excitations in 2D van der Waals materials

Katsnelson

2021

npj Comput Mater

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Despite serious effort, the nature of the magnetic interactions and the role of electron-correlation effects in magnetic two-dimensional (2D) van der Waals materials remains elusive. Using CrI3 as a model system, we show that the calculated electronic structure including nonlocal electron correlations yields spin excitations consistent with inelastic neutron-scattering measurements. Remarkably, this approach identifies an unreported correlation-enhanced interlayer super-superexchange, which rotates the magnon Dirac lines off, and introduces a gap along the high-symmetry Γ-K-M path. This discovery provides a different perspective on the gap-opening mechanism observed in CrI3, which was previously associated with spin–orbit coupling through the Dzyaloshinskii–Moriya interaction or Kitaev interaction. Our observation elucidates the critical role of electron correlations on the spin ordering and spin dynamics in magnetic van der Waals materials and demonstrates the necessity of explicit treatment of electron correlations in the broad family of 2D magnetic materials.

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“…Recent instrumental developments have improved the energy resolution of electron energy loss spectroscopy down to 4.2 meV [7,8]. This unique combination of high spatial and energy resolution opened doors to unprecedented experiments such as temperature measurement at the nanoscale [9, 10], identification and mapping of isotopically labeled molecules [11], position-and momentum-resolved mapping of phonon modes [12,13], mapping of bulk and surface modes of nanocubes [14], or investigations of the nature of polariton modes in van der Waals crystals [15].Inelastic electron scattering on atomic vibrations in a polar material consists of two major contributions, namely, impact scattering and dipolar scattering [16,17]. The latter stems from a long ranged interaction between the beam electron and an oscillating dipole moment generated by the atomic vibrations.…”

mentioning

confidence: 99%

Efficient and Versatile Model for Vibrational STEM-EELS

Zeiger

Rusz

2020

Phys. Rev. Lett.

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We introduce a novel method for the simulation of the impact scattering in vibrational scanning transmission electron microscopy electron energy loss spectroscopy (STEM-EELS) simulations. The phonon-loss process is modeled by a combination of molecular dynamics and elastic multislice calculations within a modified frozen phonon approximation. The key idea is thereby to use a so-called δ-thermostat in the classical molecular dynamics simulation to generate frequency dependent configurations of the vibrating specimen's atomic structure. The method includes correlated motion of atoms and provides vibrational spectrum images at the cost comparable to standard frozen phonon calculations. We demonstrate good agreement of our method with simulations and experiments for a 15 nm flake of hexagonal boron-nitride (hBN).Excellent spatial resolution is the highlight of the transmission electron microscope [1-6], allowing atomically resolved elemental mapping and chemistry. Recent instrumental developments have improved the energy resolution of electron energy loss spectroscopy down to 4.2 meV [7,8]. This unique combination of high spatial and energy resolution opened doors to unprecedented experiments such as temperature measurement at the nanoscale [9, 10], identification and mapping of isotopically labeled molecules [11], position-and momentum-resolved mapping of phonon modes [12,13], mapping of bulk and surface modes of nanocubes [14], or investigations of the nature of polariton modes in van der Waals crystals [15].Inelastic electron scattering on atomic vibrations in a polar material consists of two major contributions, namely, impact scattering and dipolar scattering [16,17]. The latter stems from a long ranged interaction between the beam electron and an oscillating dipole moment generated by the atomic vibrations. It can be used to perform damage-free vibrational spectroscopy in an aloof beam geometry [18,19]. High-angle impact scattering on the other hand is quite localized scattering on the atomic potential and allows for high resolution imaging and spectroscopy [17,[20][21][22].From a theoretical point of view, there is a limited number of approaches one can follow to simulate vibrational spectroscopy and imaging. Dwyer presents a treatment of both single impact and single dipolar scattering including a detailed phonon dispersion from a density functional theory calculation in a multislice scheme [23]. Forbes et al. introduced a quantum excitation of phonons model, which allows for the inclusion of thermal diffuse scattering into multislice image simulations [24]. The thermal vibrations are modeled within the Einstein model for quick image calculations, neglecting correlations in atomic movements and dispersion effects. Such an approach is not able to simulate vibrational spectra but in principle one could use different models of atomic vibrations to generate the necessary configurations. In a more recent work, Forbes et al. described a method to model the vibrational sector of the electron energy loss spectrum [25...

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Position and momentum mapping of vibrations in graphene nanostructures

Cited by 127 publications

References 23 publications

Single-atom vibrational spectroscopy in the scanning transmission electron microscope

Single-atom vibrational spectroscopy in the scanning transmission electron microscope

Electron correlation effects on exchange interactions and spin excitations in 2D van der Waals materials

Efficient and Versatile Model for Vibrational STEM-EELS

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