Quasi-particle spectrum in trilayer graphene: Role of onsite coulomb interaction and interlayer coupling

We present results of numerical calculations emphasizing the central role of the Coulomb interaction in the mechanism of d-wave Cooper pairing in layered cuprate metal-oxides. We demonstrate that many-particle Coulomb correlation described by the Coulomb vertex function Γ substantially enhances the effective electron-electron attraction in the d-wave Cooper-pairing channel in these compounds. Such a "Coulomb" mechanism of anisotropic Cooper pairing may provide high superconducting transition critical temperatures (Tc⩾100 K ) for optimum-doped cuprates.

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Graphene Domain Signature of Raman Spectra of sp2 Amorphous Carbons

Nanomaterials ◽

10.3390/nano10102021 ◽

2020 ◽

Vol 10 (10) ◽

pp. 2021

Author(s):

Elena F. Sheka ◽

Yevgeny A. Golubev ◽

Nadezhda A. Popova

Keyword(s):

Raman Spectra ◽

Molecular Spectroscopy ◽

Basic Structure ◽

Quasi Particle ◽

Phonon Spectra ◽

2D Pattern ◽

Density Delocalization ◽

Electron Density Delocalization ◽

High Degree

The standard D-G-2D pattern of Raman spectra of sp2 amorphous carbons is considered from the viewpoint of graphene domains presenting their basic structure units (BSUs) in terms of molecular spectroscopy. The molecular approximation allows connecting the characteristic D-G doublet spectra image of one-phonon spectra with a considerable dispersion of the C=C bond lengths within graphene domains, governed by size, heteroatom necklace of BSUs as well as BSUs packing. The interpretation of 2D two-phonon spectra reveals a particular role of electrical anharmonicity in the spectra formation and attributes this effect to a high degree of the electron density delocalization in graphene domains. A size-stimulated transition from molecular to quasi-particle phonon consideration of Raman spectra was experimentally traced, which allowed evaluation of a free path of optical phonons in graphene crystal.

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О природе красного сдвига G-пика раман-спектра в эпитаксиальном двумерном слое

Физика твердого тела ◽

10.21883/ftt.2021.04.50723.253 ◽

2021 ◽

Vol 63 (4) ◽

pp. 550

Author(s):

С.Ю. Давыдов ◽

О.В. Посредник

Keyword(s):

Interlayer Coupling ◽

External Pressure

With the use of the model excluded any deformation at the contact of monolayer and substrate role of the interlayer coupling is considered. It is shown that this coupling leads to the increase of the phonons frequencies values. Role of the external pressure and temperature is shortly discussed.

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Studies of Exchange Coupling in Fe/Cu/Fe(001) “Loose Spin” Structures

MRS Proceedings ◽

10.1557/proc-384-171 ◽

1995 ◽

Vol 384 ◽

Cited By ~ 5

Author(s):

M. Kowalewski ◽

B. Heinrich ◽

K. Totland ◽

J.F. Cochran ◽

S. Govorkov ◽

...

Keyword(s):

Exchange Coupling ◽

Interlayer Coupling ◽

Antiferromagnetic Coupling ◽

Concentration Limit ◽

Interlayer Exchange Coupling ◽

High Concentration ◽

Significant Difference ◽

Valence Electrons ◽

Interlayer Exchange

ABSTRACTThe interlayer exchange coupling has been studied in two trilayer structures:(a) 5.7Fe/5Cu/1FecCu1-c/5Cu/10Fe(001), where c=0.0, 0.1, 0.2, 0.45 0.60(b) 5.7Fe/5Cu/1CrcCu1-c/5Cu/10Fe(001), where c=0.1, 0.45, 0.8 and 1.0.The intention of these studies was to identify the role of Fe and Cr atoms in the alloyed FecCu1-c and CrcCu1-c layers on the direct interlayer coupling which is facilitated by the Cu valence electrons. FMR, BLS and MOKE studies were used to determine the interlayer exchange coupling. Mossbauer spectroscopy was used to identify the magnetic state of the Fe atoms in the alloyed layer. The results showed that the presence of foreign atoms inside the Cu spacer significantly decreased the bilinear antiferromagnetic coupling between the Fe layers. In the low concentration limit the Fe and Cr atoms behaved in a similar manner. A significant difference was found in the high concentration limit where the Fe atoms start to be partially magnetically ordered.

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