arXiv subjects

I. A. Nechaev

Publications and source records attributed to I. A. Nechaev.

27 records · Page 2Linked to original sources

arXiv2011

Energy Shift and Wavefunction Overlap of Metal-Organic Interface-States

The properties of Shockley-type interface states between $π$-conjugated organic molecular layers and metal surfaces are investigated by time-resolved two-photon photoemission experiments and density functional theory. For perylene- and naphthalene-tetracarboxylic acid dianhydride (PTCDA and NTCDA) adsorbed on Ag(111), a common mechanism of formation of the interface state from the partly occupied surface state of the bare Ag(111) is revealed. The energy position is found to be strongly dependent on the distance of the molecular carbon rings from the metal and their surface density. Bending of the carboxyl groups enhances the molecular overlap of the interface state.

cond-mat.other↗

arXiv2010

Quasiparticle dynamics in ferromagnetic compounds of the Co-Fe and Ni-Fe systems

We report a theoretical study of the quasiparticle lifetime and the quasiparticle mean free path caused by inelastic electron-electron scattering in ferromagnetic compounds of the Co-Fe and Ni-Fe systems. The study is based on spin-polarized calculations, which are performed within the $GW$ approximation for equiatomic and Co- and Ni-rich compounds, as well as for their constituents. We mainly focus on the spin asymmetry of the quasiparticle properties, which leads to the spin-filtering effect experimentally observed in spin-dependent transport of hot electrons and holes in the systems under study. By comparing with available experimental data on the attenuation length, we estimate the contribution of the inelastic mean free path to the latter.

cond-mat.mtrl-sci↗

arXiv2010

Inelastic decay rate of quasiparticles in a two-dimensional spin-orbit coupled electron system

We present a study of the inelastic decay rate of quasiparticles in a two-dimensional electron gas with spin-orbit interaction. The study is done within the G0W0 approximation. The spin-orbit interaction is taken in the most general form that includes both Rashba and Dresselhaus contributions linear in magnitude of the electron 2D momentum. Spin-orbit interaction effect on the inelastic decay rate is examined at different parameters characterizing the interaction strength in the electron gas.

cond-mat.other↗

arXiv2010

Ab initio study of origin and properties of a metal-organic interface state of the PTCDA/Ag(111) system

We present a detailed study of a monolayer film of 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) on Ag(111) (the PTCDA/Ag(111) system). The study is done within density functional theory with the use of the periodic slab model. The slab is chosen to contain a PTCDA monolayer film on a silver thin film of different thicknesses (6, 9, and 12 layers) with the (111) orientation. We show that one of two surface states of the pure Ag(111) films transforms into an unoccupied interface state due to the adsorbate-substrate interaction. The relation of the resulting state to the unoccupied state that has been experimentally observed in the PTCDA/Ag(111) system by scanning tunneling and two photon photoemission spectroscopy is discussed.

cond-mat.mtrl-sci↗

arXiv2006

Experimental time-resolved photoemission and ab initio study of lifetimes of excited electrons in Mo and Rh

We have studied the relaxation dynamics of optically excited electrons in molybdenum and rhodium by means of time resolved two-photon photoemission spectroscopy (TR-2PPE) and ab initio electron self-energy calculations performed within the GW and GW+T approximations. Both theoretical approaches reproduce qualitatively the experimentally observed trends and differences in the lifetimes of excited electrons in molybdenum and rhodium. For excitation energies exceeding the Fermi energy by more than 1 eV, the GW+T theory yields lifetimes in quantitative agreement with the experimental results. As one of the relevant mechanisms causing different excited state lifetime in Mo and Rh we identify the occupation of the 4d bands. An increasing occupation of the 4d bands results in an efficient decrease of the lifetime even for rather small excitation energies of a few 100 meV.

cond-mat.other↗

arXiv2006

Point-like spin-dependent interaction in calculations of self-energy ladder diagrams

An instantaneous and zero-range spin-dependent interaction, derived by summing an infinite number of electron-hole ladder diagrams within a local approximation, is analyzed as a function of the electron gas density and the relative spin polarization. The strength of such an interaction is defined by an integral of a statically screened Coulomb interaction with a spatially localized weighting factor. This weighting factor represents the mutually uncorrelated motion of an electron-hole pair in singlet or triplet spin states ($S^z=0,\pm1$). An implementation, based on a Yukawa-type interaction with a spin-polarization-dependent Thomas-Fermi screening length, is given.

cond-mat.other↗

arXiv2006

Multiple electron-hole scattering effect on quasiparticle properties in a homogeneous electron gas

We present a detailed study of a contribution of the T matrix accounting for multiple scattering between an electron and a hole to the quasiparticle self-energy. This contribution is considered as an additional term to the GW self-energy. The study is based on a variational solution of the T-matrix integral equation within a local approximation. A key quantity of such a solution, the local electron-hole interaction, is obtained at the small four-momentum transfer limit. Performed by making use of this limit form, extensive calculations of quasiparticle properties in the homogeneous electron gas over a broad range of electron densities are reported. We carry out an analysis of how the T-matrix contribution affects the quasiparticle damping rate, the quasiparticle energy, the renormalization constant, and the effective mass enhancement. We find that in comparison with the GW approximation the inclusion of the T matrix leads to an essential increase of the damping rate, a slight reduction of the GW band narrowing, a decrease of the renormalization constant at the Fermi wave vector, and some "weighting" of quasiparticles at the Fermi surface.

cond-mat.other↗

arXiv2005

Induced Charge-Density Oscillations at Metal Surfaces

Induced charge-density (ICD) oscillations at the Cu(111) surface caused by an external impurity are studied within linear response theory. The calculation takes into account such properties of the Cu(111) surface electronic structure as an energy gap for three-dimensional (3D) bulk electrons and a $s-p_z$ surface state that forms two-dimensional (2D) electron system. It is demonstrated that the coexistence of these 2D and 3D electron systems has profound impact on the ICD in the surface region. In the case of a static impurity the characteristic ICD oscillations with the $1/ρ^2$ decay as a function of lateral distance, $ρ$, are established in both electron systems. For the impurity with a periodically time-varying potential, the novel dominant ICD oscillations which fall off like $\sim1/ρ$ are predicted.

cond-mat.soft↗

arXiv2005

Variational solution of the T-matrix integral equation

We present a variational solution of the T-matrix integral equation within a local approximation. This solution provides a simple form for the T matrix similar to Hubbard models but with the local interaction depending on momentum and frequency. By examining the ladder diagrams for irreducible polarizability, a connection between this interaction and the local-field factor is established. Based on the obtained solution, a form for the T-matrix contribution to the electron self-energy in addition to the GW term is proposed. In the case of the electron-hole multiple scattering, this form allows one to avoid double counting.

cond-mat.other↗