Communication: Momentum-resolved quantum interference in optically excited surface states

Abstract

Surface states play essential roles in condensed matter physics, e.g., as model two-dimensional (2D) electron gases and as the basis for topological insulators. Here, we demonstrate quantum interference in the optical excitation of 2D surface states using the model system of C60/Au(111). These surface states are transiently populated and probed in a femtosecond time- and angle-resolved two-photon photoemission experiment. We observe quantum interference within the excited populations of these surface states as a function of parallel momentum vector. Such quantum interference in momentum space may allow one to control 2D transport properties by optical fields.

Two-State Double-Continuum Fano Resonance at the Si(100) Surface

“…For the Si(100) surface the two-photon photoemission (2PPE) intensity exhibits complex interference phenomena as a function of the excitation energy, which can be explained by a two-state double-continuum extension of Fano's theory. Our observations and modeling are general and clarify unexplained intensity variations in optical absorption, for example, at surfaces [14], in nanostructures [15], and organic thin films on inorganic substrates [16].…”

“…For the Si(100) surface the two-photon photoemission (2PPE) intensity exhibits complex interference phenomena as a function of the excitation energy, which can be explained by a two-state double-continuum extension of Fano's theory. Our observations and modeling are general and clarify unexplained intensity variations in optical absorption, for example, at surfaces [14], in nanostructures [15], and organic thin films on inorganic substrates [16].As the Si(100) surface is the most important template for semiconductor device fabrication, a detailed description of its electronic structure has been developed [17][18][19][20]. The formation of surface dimers results in a (2 Â 1) reconstruction at room temperature and a semiconducting surface with occupied and empty dangling-bond bands D up and D down .…”

Electronic structure and dynamics of quasi-2D states of vanadyl naphthalocyanine on Au(111)†

“…Inspecting once more the optical resonance in the n = 2 IPR manifold in Figure 11, we find that as a function of excitation energy the intensities of the Shockley state and the n = 2 IPR experience 'intensity switching' upon crossing the resonance: below resonance the IPR generally dominates, while above resonance the Shockley surface state carries most of the excitation cross-section. This is reminiscent of the asymmetric intensity distributions for the image potential states on Si(100) and for C 60 /Au(111) in k-space, where the observation of quantum interference was reported [26][27][28].…”

“…Fano resonances on surfaces have indeed been observed recently on Si(100) and in momentum-space maps of C 60 on Au(111) [27,28]. The IPR on Au(111) provides thus a model system to measure directly factors controlling the coupling of a confined quasi-2D quantum system to a continuum, the fingerprints of which are expected to appear in the TPPE excitation spectra.…”

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

“…6) might be based on the assumption of a strongly anisotropic dephasing time, caused by elastic scattering from the step edges, that changes the population dynamics within individual momentum windows and additionally modulates the total 2PPE yield as a function of k y [50,53]. A finite dephasing time T * 2 influences both the maximum population of the intermediate state as well as the time of maximum population.…”