Theory of two-photon photoemission spectroscopy of surfaces

Ueba, H.; Gumhalter, B.

doi:10.1016/j.progsurf.2007.03.002

Cited by 79 publications

(68 citation statements)

References 68 publications

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“…Dynamics of electronic excitations at metal surfaces has been widely investigated both experimentally (1-6) and theoretically (5,(7)(8)(9)(10)(11)(12)(13). As a consequence, deep understanding has been reached about the mechanisms ruling electron decay and electron charge transfer.…”

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confidence: 99%

Time-dependent electron phenomena at surfaces

Muiño

Sánchez‐Portal

Silkin

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Femtosecond and subfemtosecond time scales typically rule electron dynamics at metal surfaces. Recent advance in experimental techniques permits now remarkable precision in the description of these processes. In particular, shorter time scales, smaller system sizes, and spin-dependent effects are current targets of interest. In this article, we use state-of-the-art theoretical methods to analyze these refined features of electron dynamics. We show that the screening of localized charges at metal surfaces is created locally in the attosecond time scale, while collective excitations transfer the perturbation to larger distances in longer time scales. We predict that the elastic width of the resonance in excited alkali adsorbates on ferromagnetic surfaces can depend on spin orientation in a counterintuitive way. Finally, we quantitatively evaluate the electron-electron and electron-phonon contributions to the electronic excited states widths in ultrathin metal layers. We conclude that confinement and spin effects are key factors in the behavior of electron dynamics at metal surfaces.lifetimes | spin effects | time-dependent phenomena C hemistry is driven by electrons. Chemical dynamics is often determined by electron dynamics, with electronically excited states frequently acting as necessary intermediate steps in chemical activity. The understanding and control of charge transfer times and electronic excitation survival times is thus a necessary step to understand, control, and design physical and chemical processes at surfaces.Dynamics of electronic excitations at metal surfaces has been widely investigated both experimentally (1-6) and theoretically (5, 7-13). As a consequence, deep understanding has been reached about the mechanisms ruling electron decay and electron charge transfer. However, recent advances in experimental tools are raising new challenges, many of them linked to shorter time scales, smaller system sizes, and/or spin effects. In this article, we present fresh results on these expanding topics, in an effort to blaze trails in electron dynamics research.At surfaces, electron excitation, charge exchange, and electron decay typically take place in the femtosecond (fs) and attosecond (as) time scales (1 as ¼ 10 −18 s, 1 fs ¼ 10 −15 s) (i.e., at times much faster than any nuclear motion). Advance in laser-based experimental techniques has carried research on this field to a new frontier, in which direct measurements of electron processes in this time scale are possible. Attosecond spectroscopy, for instance, is nowadays able to discern the individual elementary steps in photoemission from surfaces (i.e., excitation, transport, and emission) (14, 15). Access to experimental information in the attosecond scale is asking for new theoretical concepts. In particular, one of the relevant questions is how electronic excitations are created in time and how the environment reacts in such time scale. In the photocreation of localized holes in adsorbates at metallic surfaces, this question can be reformulated as...

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mentioning

confidence: 99%

Time-dependent electron phenomena at surfaces

Muiño

Sánchez‐Portal

Silkin

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…A non-Markovian evolution of the survival probability decaying faster than Eq. ͑38͒ will manifest itself through the modifications of relative intensities of direct and indirect transitions in 2PPE and of the peak shapes in PE, IPE, and 2PPE spectra from surface bands relative to the ones deduced from the asymptotic approaches 18,46,47 utilizing Eq. ͑38͒.…”

Section: Discussionmentioning

confidence: 99%

“…17,18 However, the phenomenologically introduced rate constants do not carry information on the early quasiparticle evolution and hence the validity of this approach is restricted to the asymptotic regime in which the time scale͑s͒ of perturbation of the system by external probe͑s͒ is separated from the time scale of relaxation processes that affect spectral shapes. 6,18 To overcome this shortcoming of the phenomenological approaches we develop in the present paper a microscopic description of presymptotic evolution of electrons and holes subsequent to their promotion into the surface localized states. The formalism is applied to illustrate and interpret ultrafast quasiparticle dynamics in Q2D bands on the benchmark Cu͑111͒ surface in the course of spectroscopic measurements.…”

Section: Introductionmentioning

confidence: 99%

“…In concluding Sec. IV we summarize the main results of application of the developed formalism to description of quasiparticle dynamics in surface bands and discuss its merits in the context of complementing and refining the earlier theoretical treatments of ultrafast dynamics in which the decoherence and decay of quasiparticles were introduced either on a semiphenomenological basis 13,17,18 or were restricted to asymptotic regimes. 7,8 To facilitate applications of the developed description in interpretations of time resolved measurements we formulate a simple interpolation scheme for fitting the non-Markovian ultrafast decay of quasiparticles that could be used for analyzing the results of high resolution spectroscopic studies.…”

Section: Introductionmentioning

confidence: 99%

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Ultrafast dynamics and decoherence of quasiparticles in surface bands: Preasymptotic decay and dephasing of quasiparticle states

et al. 2007

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We develop a many-body description of ultrafast electron dynamics in surface bands appropriate for studying relaxation of hot electrons and holes excited in the processes of one-and two-photon photoemission and inverse photoemission from surfaces. The description is based on the formalism for calculation of quasiparticle survival probabilities combined with self-consistent treatment of the electronic response of the system. We show that the calculation of survival amplitudes which carry information on the quasiparticle decay and decoherence can be conveniently mapped onto the problem of renormalization of quasiparticles by the interactions with bosonized excitations constituting the system heatbath. Applying this approach to the benchmark Cu͑111͒ surface we are able to assess the regimes of preasymptotic non-Markovian quasiparticle dynamics in surface bands and locate transitions to the regime of exponential decay governed by the modified Fermi golden rule-type of transition rates. The general validity of these findings enables us to establish borderlines between different regimes of ultrafast electronic relaxation and on that basis to introduce a simple interpolation scheme for modeling of quasiparticle decay in the course of spectroscopic measurements.

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“…In contrast to the momentum-averaged analysis, the momentum-dependent population dynamics cannot be described by means of the simple rate-equation approach under the constraint of a fixed pulse cross correlation. In particular, the time delays of the population maxima, which are known to be an effective measure of the states lifetime [39,40], cannot be reproduced. This is indicated by the dash-dotted line in Fig.…”

Section: B Analysis Of Relaxation Dynamicsmentioning

confidence: 99%

Unoccupied electronic structure and momentum-dependent scattering dynamics in Pb/Si(557) nanowire arrays

et al. 2015

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The unoccupied electronic structure of quasi-one-dimensional reconstructions of Pb atoms on a Si(557) surface is investigated by means of femtosecond time-and angle-resolved two-photon photoemission. Two distinct unoccupied electronic states are observed at E − E F = 3.55 and 3.30 eV, respectively. Density functional theory calculations reveal that these states are spatially located predominantly on the lead wires and that they are energetically degenerated with an energy window of reduced electronic density of states in Si. We further find momentum-averaged lifetimes of 24 and 35 fs of these two states, respectively. The photoemission yield and the population dynamics depend on the electron momentum component perpendicular to the steps of the Si substrate, and the momentum-dependent dynamics cannot be described by means of rate equations. We conclude that momentum-and direction-dependent dephasing of the electronic excitations, likely caused by elastic scattering at the step edges on the vicinal surface, modifies the excited-state population dynamics in this system.

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Theory of two-photon photoemission spectroscopy of surfaces

Cited by 79 publications

References 68 publications

Time-dependent electron phenomena at surfaces

Time-dependent electron phenomena at surfaces

Ultrafast dynamics and decoherence of quasiparticles in surface bands: Preasymptotic decay and dephasing of quasiparticle states

Unoccupied electronic structure and momentum-dependent scattering dynamics in Pb/Si(557) nanowire arrays

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