Bulk Excitonic Effects in Surface Optical Spectra

Hahn, P. H.; Schmidt, Wolf Gero; Bechstedt, F.

doi:10.1103/physrevlett.88.016402

Cited by 128 publications

(97 citation statements)

References 32 publications

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“…Quasiparticle calculations for the high-symmetry points of the hexagon model surface band structure found self-energy effects to increase the lowest transition energies by 0.26 eV on average [13]. A larger shift of 0.5 eV, typical for Si excitation energies [35], applies to the higher energy negative optical anisotropies, because the optical transitions involve Si states [32]. Allowing for these energy shifts, the agreement between the calculated and measured RAS spectra is truly impressive.…”

Section: Prl 102 226805 (2009) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 83%

“…The underestimation of excitation energies is typical for DFT calculations where self-energy effects are neglected. The complexity and size of the In nanowire structure prevents the calculation of optical spectra using many-body perturbation theory that includes self-energy and excitonic effects [35]. Quasiparticle calculations for the high-symmetry points of the hexagon model surface band structure found self-energy effects to increase the lowest transition energies by 0.26 eV on average [13].…”

Section: Prl 102 226805 (2009) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

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Structure of Si(111)-In Nanowires Determined from the Midinfrared Optical Response

Chandola

Hinrichs²,

Gensch³

et al. 2009

Phys. Rev. Lett.

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The anisotropic optical response of Sið111Þ À ð4 Â 1Þ=ð8 Â 2Þ-In in the midinfrared, where ab initio studies predict significant changes in the band structure between competing models of this important quasi-1D system, has been measured using infrared spectroscopic ellipsometry (IRSE) and reflection anisotropy spectroscopy (RAS). Both IRSE and RAS of the (8 Â 2) phase show that the anisotropic Drude tail of the (4 Â 1) phase is replaced by two peaks at 0.50 and 0.72 eV, which appear in ab initio optical response calculations for the hexagon model of the (8 Â 2) structure, but not the trimer model.

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Section: Prl 102 226805 (2009) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 83%

Section: Prl 102 226805 (2009) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Structure of Si(111)-In Nanowires Determined from the Midinfrared Optical Response

Chandola

Hinrichs²,

Gensch³

et al. 2009

Phys. Rev. Lett.

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“…Based on the electronic structure obtained within DFT-LDA, we calculate the reflectance anisotropy in the independent-particle approximation following Del Sole [24] and Manghi et al [25]. Optical spectra are usually strongly influenced by many-body effects such as self-energy corrections and electron-hole attraction [26]. In the case of RAS, however, some error cancellation occurs: RAS spectra are difference spectra, normalized to the bulk dielectric function (cf.…”

Section: Computationalmentioning

confidence: 99%

Gallium‐rich reconstructions on GaAs(001)

Pristovsek

Tsukamoto

Ohtake

et al. 2003

Physica Status Solidi (b)

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Ga-rich reconstructions on GaAs(001) surfaces were prepared by annealing and Ga dosing of Molecular Beam Epitaxy grown samples and analyzed in-situ by Reflectance Anisotropy Spectroscopy and Reflection High-Energy Electron Diffraction. Annealing or dosing gallium above about 800 K invariably results in a (4 Â 2)/c(8 Â 2) reconstruction. Lowering the temperature or annealing below 800 K results in a (2 Â 6)/(3 Â 6) reconstruction. By dosing the (2 Â 6)/(3 Â 6) reconstruction with more than 0.2 monolayer of gallium, it transforms into a (4 Â 6) reconstruction. The observed translational symmetries and measured RAS spectra are compared with results of first-principles calculations. None of the (2 Â 6) structures proposed in the literature is energetically stable. The RAS spectrum calculated for the z(4 Â 2) model resembles reasonably the data measured for the (4 Â 2) surface. The RAS spectra calculated for (2 Â 6) symmetries indicate that mixed Ga-As dimers likely are a structural element of the corresponding surface reconstructions.

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“…Other scalings, namely, M 8 or M 10 , are obtained by also including triply or quadruply excited determinants. The approaches which will be discussed in this review can exhibit a much better scaling, according to the system and to the numerical implementation (Benedict et al, 1998a;Hahn et al, 2002;Vasiliev et al, 2002).…”

Section: Overviewmentioning

confidence: 99%

Electronic excitations: density-functional versus many-body Green’s-function approaches

2002

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Electronic excitations lie at the origin of most of the commonly measured spectra. However, the first-principles computation of excited states requires a larger effort than ground-state calculations, which can be very efficiently carried out within density-functional theory. On the other hand, two theoretical and computational tools have come to prominence for the description of electronic excitations. One of them, many-body perturbation theory, is based on a set of Green's-function equations, starting with a one-electron propagator and considering the electron-hole Green's function for the response. Key ingredients are the electron's self-energy ⌺ and the electron-hole interaction. A good approximation for ⌺ is obtained with Hedin's GW approach, using density-functional theory as a zero-order solution. First-principles GW calculations for real systems have been successfully carried out since the 1980s. Similarly, the electron-hole interaction is well described by the Bethe-Salpeter equation, via a functional derivative of ⌺. An alternative approach to calculating electronic excitations is the time-dependent density-functional theory (TDDFT), which offers the important practical advantage of a dependence on density rather than on multivariable Green's functions. This approach leads to a screening equation similar to the Bethe-Salpeter one, but with a two-point, rather than a four-point, interaction kernel. At present, the simple adiabatic local-density approximation has given promising results for finite systems, but has significant deficiencies in the description of absorption spectra in solids, leading to wrong excitation energies, the absence of bound excitonic states, and appreciable distortions of the spectral line shapes. The search for improved TDDFT potentials and kernels is hence a subject of increasing interest. It can be addressed within the framework of many-body perturbation theory: in fact, both the Green's functions and the TDDFT approaches profit from mutual insight. This review compares the theoretical and practical aspects of the two approaches and their specific numerical implementations, and presents an overview of accomplishments and work in progress. CONTENTS

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Bulk Excitonic Effects in Surface Optical Spectra

Cited by 128 publications

References 32 publications

Structure of Si(111)-In Nanowires Determined from the Midinfrared Optical Response

Structure of Si(111)-In Nanowires Determined from the Midinfrared Optical Response

Gallium‐rich reconstructions on GaAs(001)

Electronic excitations: density-functional versus many-body Green’s-function approaches

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