Fermi surface mapping with photoelectrons at UV energies

Aebi, Philipp; Osterwalder, Jürg; Fasel, Román; Naumović, D.; Schlapbach, L.

doi:10.1016/0039-6028(94)91515-6

Cited by 102 publications

(77 citation statements)

References 12 publications

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“…This is especially important when one has to rely on ARPES spectral intensities as is the case in an analysis of the momentum distribution function 7,15 n(k) ͑the momentum-integrated spectral intensity͒ and in the angle-scanning mode of angle-resolved photoelectron spectroscopy. 21 The Ames Laboratory is operated by Iowa State University for the U.S. DOE under Contract No. W-7405-ENG-82.…”

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confidence: 99%

Evidence for a strong impact of the electron-photon matrix element on angle-resolved photoelectron spectra of layered cuprate compounds

et al. 2000

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Evidence for a strong impact of the electron-photon matrix element on angle-resolved photoelectron spectra of layered cuprate compounds

et al. 2000

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“…Angle-resolved photoemission spectroscopy (ARPES) has emerged as probably the most powerful tool for determining the occupied electronic band structure of solids and their surfaces. Recently, it has been extensively applied to gain insight into the topology of Fermi surfaces of a variety of materials ranging from conventional three-dimensional metals like W and Cu [1,2,3] to quasi two dimensional layered compounds [4,5,6], purple bronzes [7] and high T C cuprate materials [8,9]. The accuracy of the determination of the Fermi surface by ARPES, however, has never been questioned and it turns out that even for the extensively studied BiSrCaCuO it is not at all clear that the topology of the normal state FS shows hole-like pockets around the corners of the Brillouin zone [8,9,10] or electron-pockets around the center of the BZ [11].…”

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How to Determine Fermi Vectors by Angle-Resolved Photoemission

et al. 1999

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Angle resolved photoemission spectroscopy (ARPES) has been commonly applied to evaluate the shape of Fermi surfaces by employing simple criteria for the determination of the Fermi vector kF parallel to the surface such as maximum photoemission intensity at the Fermi level or discontinuity in the momentum distribution function. Here we show that these criteria may lead to large uncertainties in particular for narrow band systems. We develop a reliable method for the determination of Fermi vectors employing high resolution ARPES at different temperatures. The relevance and accuracy of the method is discussed on data of the quasi two dimensional system TiTe2.A wide variety of physical phenomena of crystalline materials, such as e. g. transport, optical and magnetic response, and phase transitions rely on details of the topology of the Fermi surface (FS). Its experimental determination performed by traditional techniques like de Haas-van Alphen effect, magnetoacoustic effect, Compton scattering, or positron annihilation have, however, been restricted to bulk materials. All techniques in common is the indirect information on the shape of the Fermi surface. While the first two determine extremal crosssections of FS's in a plane normal to the applied magnetic field, the latter yield information on one and two dimensional projections of FS's. More complex cases, such as superlattices, heterostructures or even clean surfaces can also hardly be accessed. Angle-resolved photoemission spectroscopy (ARPES) has emerged as probably the most powerful tool for determining the occupied electronic band structure of solids and their surfaces. Recently, it has been extensively applied to gain insight into the topology of Fermi surfaces of a variety of materials ranging from conventional three-dimensional metals like W and Cu [1,2,3] to quasi two dimensional layered compounds [4,5,6], purple bronzes [7] and high T C cuprate materials [8,9]. The accuracy of the determination of the Fermi surface by ARPES, however, has never been questioned and it turns out that even for the extensively studied BiSrCaCuO it is not at all clear that the topology of the normal state FS shows hole-like pockets around the corners of the Brillouin zone [8,9,10] or electron-pockets around the center of the BZ [11].It is widely assumed that ARPES measures the spectral function A(k, ω) of the one-particle system times the Fermi function f (ω) and matrix elements do not play a significant role (see e.g. ref. [12,13]). This motivates studies of band dispersions, line shapes, momentum distribution functions, and Fermi surfaces. Fermi vectors have been extracted from ARPES data employing criteria like (i) maximum ARPES intensity at the Fermi level E F [1,2,7,8,14], (ii) max|∇ k | of the energy integrated photoemission intensity [4,5,15,16] or (iii) fitting ARPES peak positions over several emission angles and extrapolating the dispersion to E F [17]. However, none of these techniques explicitly considers the detailed mechanism of the photoemission process. In part...

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“…In the present work we use sequential angle-scanning data acquisition [14], providing a high energy resolution and access to a wide range in k space. Recently we demonstrated the efficiency and accuracy of this method by measuring the two-dimensional FS of a Bi cuprate [15] and cuts through the three-dimensional FS of Cu [16]. The obvious advantage of this procedure is that it provides a very accurate intensity mapping with a selectable uniform sampling density.…”

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“…Judging from these data, the violation of the conservation of the wave vector component perpendicular to the surface ͑k Ќ ͒ does not appear to be too severe. The mapping corresponds to a section through the FS perpendicular to the [110] direction as has been demonstrated in [16] for the example of Cu. Intensities are modulated along these lines due to matrix element effects.…”

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k-Space Mapping of Majority and Minority Bands on the Fermi Surface of Nickel below and above the Curie Temperature

et al. 1996

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A section through the three-dimensional Fermi surface of Ni has been mapped perpendicular to the [110] direction using angle-scanned photoemission. Regions of minority and majority spin bands, well separated in k space, can clearly be identified through comparison with a band structure calculation. The behavior of the different bands is observed for temperatures below and above the Curie temperature T C . We find bands which move and bands which stay in place for going from T , T C to T . T C .Despite a large amount of experimental data on the electronic and magnetic structure of nickel, conflicting conclusions persist about the behavior of the exchange splitting DE ex as a function of temperature [1][2][3][4][5]: While some experiments point to a largely temperatureindependent exchange splitting in going across the Curie temperature (T C 631 K) others give evidence for changes of the Fermi surface (FS) in traversing T C . Insight into this question has also been gained from photoemission and inverse photoemission experiments [6][7][8][9][10][11][12], and again conflicting views were obtained with respect to the temperature dependence of DE ex . Recent experiments found that spin-split bands merged with temperature at some k locations while their splitting remained temperature independent at others [10]. Inverse photoemission studies [12] reported on collapsing spinsplit bands upon approaching T C even for the magnetic Z 2 band, and the experimentally determined exchange splitting followed the rescaled bulk magnetization curve.Considering these results showing both temperatureindependent or collapsing exchange splittings, and thus indicating at the same time the persistence of local moments and a Stoner-type behavior, it is important to obtain a more systematic view of the temperature behavior of DE ex in k space, and, in particular, of the magnetic bands crossing the Fermi level ͑E F ͒. We therefore present a highresolution temperature-dependent mapping of a complete section through the FS of Ni, as viewed through the (110) surface, in which several magnetic bands are observed at the same time. It is important to note that the present experiment resolves majority and minority bands in k space.Recently, Santoni et al.[13] used a two-dimensional display-type analyzer to map the FS of layered graphite directly by measuring the total photoelectron intensity within a narrow energy window at E F . High intensities are recorded at locations of the wave vector component parallel to the surface ͑k k ͒ where direct transitions disperse through this window, namely, through the FS. In the present work we use sequential angle-scanning data acquisition [14], providing a high energy resolution and access to a wide range in k space. Recently we demonstrated the efficiency and accuracy of this method by measuring the two-dimensional FS of a Bi cuprate [15] and cuts through the three-dimensional FS of Cu [16]. The obvious advantage of this procedure is that it provides a very accurate intensity mapping with a selectable uniform ...

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Fermi surface mapping with photoelectrons at UV energies

Cited by 102 publications

References 12 publications

Evidence for a strong impact of the electron-photon matrix element on angle-resolved photoelectron spectra of layered cuprate compounds

Evidence for a strong impact of the electron-photon matrix element on angle-resolved photoelectron spectra of layered cuprate compounds

How to Determine Fermi Vectors by Angle-Resolved Photoemission

k-Space Mapping of Majority and Minority Bands on the Fermi Surface of Nickel below and above the Curie Temperature

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