1,069 research outputs found
Competing rhombohedral and monoclinic crystal structures in Mn compounds: an {\em ab-initio} study
Based on the relativistic spin-polarized density functional theory
calculations we investigate the crystal structure, electronic and magnetic
properties of a family MnPn2Ch4 compounds, where pnictogen metal atoms (Pn) are
Sb and Bi; chalcogens (Ch) are Se, Te. We show that in the series the compounds
of this family with heavier elements prefer to adopt rhombohedral crystal
structure composed of weakly bonded septuple monoatomic layers while those with
lighter elements tend to be in the monoclinic structure. Irrespective of the
crystal structure all compounds of the MnPn2Ch4 series demonstrate a weak
energy gain (of a few meV per formula unit or even smaller than meV) for
antiferromagnetic (AFM) coupling for magnetic moments on Mn atoms with respect
to their ferromagnetic (FM) state. For rhombohedral structures the interlayer
AFM coupling is preferable while in monoclinic phases intralayer AFM
configuration with ferromagnetic ordering along the Mn chain and
antiferromagnetic ordering between the chains has a minimum energy. Over the
series the monoclinic compounds are characterized by substantially wider
bandgap than compounds with rhombohedral structure
Electron-phonon interaction at the Be(0001) surface
We present a first principle study of the electron-phonon (e-p) interaction
at the Be(0001) surface. The real and imaginary part of the e-p self energy are
calculated for the surface state in the binding energy range from the
point to the Fermi level. Our calculation shows an overall good
agreement with several photoemission data measured at high and low
temperatures. Additionally, we show that the energy derivative of real part of
the self-energy presents a strong temperature and energy variation close to
, making it difficult to measure its value just at .Comment: Accepted in Phys. Rev. Lett., 5 figure
Surface-state electron dynamics in noble metals
Theoretical investigations of surface-state electron dynamics in noble metals
are reported. The dynamically screened interaction is computed, within
many-body theory, by going beyond a free-electron description of the metal
surface. Calculations of the inelastic linewidth of Shockley surface-state
electrons and holes in these materials are also presented. While the linewidth
of excited holes at the surface-state band edge () is
dominated by a two-dimensional decay channel, within the surface-state band
itself, our calculations indicate that major contributions to the
electron-electron interaction of surface-state electrons above the Fermi level
come from the underlying bulk electrons.Comment: 17 pages, 7 figures, to appear in Prog. Surf. Sc
Ultrafast electron dynamics in metals
During the last decade, significant progress has been achieved in the rapidly
growing field of the dynamics of {\it hot} carriers in metals. Here we present
an overview of the recent achievements in the theoretical understanding of
electron dynamics in metals, and focus on the theoretical description of the
inelastic lifetime of excited hot electrons. We outline theoretical
formulations of the hot-electron lifetime that is originated in the inelastic
scattering of the excited {\it quasiparticle} with occupied states below the
Fermi level of the solid. {\it First-principles} many-body calculations are
reviewed. Related work and future directions are also addressed.Comment: 17 pages, two columns, 13 figures, to appear in ChemPhysChe
Spin-helical Dirac states in graphene induced by polar-substrate surfaces with giant spin-orbit interaction: a new platform for spintronics
Spintronics, or spin electronics, is aimed at efficient control and
manipulation of spin degrees of freedom in electron systems. To comply with
demands of nowaday spintronics, the studies of electron systems hosting giant
spin-orbit-split electron states have become one of the most important
directions providing us with a basis for desirable spintronics devices. In
construction of such devices, it is also tempting to involve graphene, which
has attracted great attention because of its unique and remarkable electronic
properties and was recognized as a viable replacement for silicon in
electronics. In this case, a challenging goal is to make graphene Dirac states
spin-polarized. Here, we report on absolutely new promising pathway to create
spin-polarized Dirac states based on coupling of graphene and polar-substrate
surface states with giant Rashba-type spin-splitting. We demonstrate how the
spin-helical Dirac states are formed in graphene deposited on the surface of
BiTeCl. This coupling induces spin separation of the originally spin-degenerate
graphene states and results in fully helical in-plane spin polarization of the
Dirac electrons.Comment: 5 pages, 3 figure
Ideal two-dimensional electron systems with a giant Rashba-type spin splitting in real materials: surfaces of bismuth tellurohalides
Spintronics is aimed at active controlling and manipulating the spin degrees
of freedom in semiconductor devices. A promising way to achieve this goal is to
make use of the tunable Rashba effect that relies on the spin-orbit interaction
(SOI) in a two-dimensional (2D) electron system immersed in an
inversion-asymmetric environment. The SOI induced spin-splitting of the
2D-electron state provides a basis for many theoretically proposed spintronic
devices. However, the lack of semiconductors with large Rashba effect hinders
realization of these devices in actual practice. Here we report on a giant
Rashba-type spin splitting in 2D electron systems which reside at
tellurium-terminated surfaces of bismuth tellurohalides. Among these
semiconductors, BiTeCl stands out for its isotropic metallic surface-state band
with the Gamma-point energy lying deep inside the bulk band gap. The giant
spin-splitting of this band ensures a substantial spin asymmetry of the
inelastic mean free path of quasiparticles with different spin orientations.Comment: 12 pages, 5 figure
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