Lifetimes of electronic excitations in unoccupied surface states and the image potential states on Pd(110)
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ONIC PROPERTIES OF SOLID
Lifetimes of Electronic Excitations in Unoccupied Surface States and the Image Potential States on Pd(110) S. S. Tsirkina,b, S. V. Eremeeva,c, and E. V. Chulkovb,d a
Tomsk State University, Tomsk, 634050 Russia Donostia International Physics Center (DIPC), San Sebastian/Donostia, Basque Country, 20018 Spain cInstitute of Strength Physics and Materials Science, Siberian Branch, Russian Academy of Sciences, Tomsk, 634021 Russia d Departamento de Física de Materiales and Centro de Física de Materiales (CFM)–Materials Physics Center (MPC), San Sebastian/Donostia, Basque Country, 20018 Spain Facultad de Ciencias Quimicas, UPV/EHU, San Sebastian/Donostia, Basque Country, 20080 Spain email: [email protected] b
Received February 18, 2012
Abstract—The contribution of inelastic electron–electron scattering to the decay rate of excitations in the surface states and first two image potential states at the Y point on the surface is calculated in the GW approx imation, and the quasimomentum dependence of the corresponding contribution for the surface states is analyzed. The mechanisms of electron scattering in these states are studied, and the temperature dependence of the excitation lifetime is analyzed with allowance for the contribution of the electron–phonon interaction calculated earlier. DOI: 10.1134/S1063776112090154
1. INTRODUCTION A large number of recent theoretical and experi mental studies have been devoted to the dynamics of electrons and holes in the bulk states [1–6], surface states, and the image potential states on clean metal surfaces [7–16], as well as the dynamics of excitations appearing on the surface upon the deposition of thin films [16–21], adatoms [22–26], nanoislands [27], and nanopyramids [28]. The interest in this field is due to the important role of electronic excitations in vari ous physical phenomena such as desorption [29], cat alytic reactions [30, 31], and epitaxial growth [32]. Information on the lifetime τ of quasiparticles is often obtained from measuring the width Γ of the pho toemission peak corresponding to a given state, which is related to the lifetime by the relation Γ = ប/τ. The linewidth consists of the contributions from scattering via three channels: inelastic electron–electron scat tering (Γe–e), electron–phonon scattering (Γe–ph), and scattering on defects (Γe–d). Scattering width Γe–e is independent of temperature, and the thermal broad ening of the line is determined by the electron– phonon scattering [35, 39] and scattering on thermally activated defects [36, 37]. Most studies were performed for closepacked sur faces [13, 14, 33, 34, 39] and only a few publications contained estimates of excitation lifetimes on open surfaces [38, 40–42]. However, more open surfaces such as the (110) surfaces of fcc metals are of special interest, in particular, due to their high catalytic activ
ity [43]. The ab initio calculations of lifetime require considerable computational resources [33, 34, 38]; therefore, the description of the dynamics of surf
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