Diploma - Max Planck Institute for Solid State Research

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52 4 EuRh 2 Si 2 – semi-localized electrons Figure 4.19: simulated spectra based on the distribution of V ij (k) derived in ch. 4.2.2; (a) to (c) the evolving triangularlyshaped area A1 by increasing the number of projected bands from 1 to 50 bands, respectively (d) hybridization of the linear surface state around Γ with the final state multiplet, whereat the apex remains above the Fermi level (e) projected bulk band structure in A2 which hybridizes with the 4f states to form a shaded area below the surface state S1 (f) final spectrum containing all parts of the band structure which contribute to the hybrid states Figure 4.20: measured dispersion for X−Γ−M and modelled spectra for Eu and Si terminated surfaces. The colormaps are only vaguely adopted since two different programs have been used to create the figures. (a) show the simulated f emission and (b) the measured spectrum (hν = 120 eV, linear vertical polarization, T ≈ 10 K) dominated due to the cross section by f character for Si terminated surfaces; (c) + (d) depict the respective results for the Eu terminated surface. Differences between measurement and simulation are marked by numbers and discussed in the text.
4.3 Perspective: quasi-linear dispersion in a 4f compound 53 Figure 4.21: dispersion of the linear surface state S1 around Γ measured for several cuts parallel to Γ−X towards the X-point. The different cuts are sketched in (c). In (a) are the results for Si terminated surface and in (b) for Eu terminated surface depicted. (SLS-SIS) Therefore using atomic excitation spectra is only a zeroth-order approach. In principle, a model for atomic 4f emission with additional, non-spherical potential could address both shortcomings. Furthermore, the additional spectral weight at Γ cannot be explained (4). Nevertheless, the splitting of the surface 4f emission evident in fig. 4.9 can be explained in the framework of hybridization, because the surface state S2 seems to displace the spectral weight to higher and lower binding energies with a simultaneously emerging hybridization gap (5). As presented, the PE spectra show mainly surface states in hybridization with the 4f multiplet of europium. Since the momentum perpendicular to the surface is not conserved, shaded bands (part of the projected band structure) emerge additionally. To disentangle the bulk band structure successfully, a less surface sensitive method has to be chosen. On the other hand, PE is a good choice to describe surface and edge states. This is especially important in a new class of solids, the surface states of which have macroscopically-different properties – e.g. the bulk is an insulator whereat the surface is a metal. A short outline will be given in the next chapter. 4.3 Perspective: quasi-linear dispersion in a 4f compound Dimensionality and thereby confined electronic states are of recent interest in current research [75–78]. Especially after certain topological insulators have been predicted [76] and experimentally explored [77], the surface of which is stable metallic, a new field of research has emerged for spintronic and magnetoelectric devices. The topological classification scheme [76, 79] allows to determine whether the surface states are expected to be stable under small pertubation (e.g. disorder). It is expected, that due to supressed back-scattering in the case of strong topological insulators [75], dissipationless transport
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- Photoemission on EuRh 2 Si 2 - di
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Abstract A thorough knowledge of co
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vii Nomenclature AF APW ARPES BO BZ
Page 10 and 11: 2 1 Introduction conflicting limits
Page 12 and 13: 4 2 Theoretical foundation fore the
Page 14 and 15: 6 2 Theoretical foundation system a
Page 16 and 17: 8 2 Theoretical foundation such a s
Page 18 and 19: 10 2 Theoretical foundation Figure
Page 20 and 21: 12 2 Theoretical foundation Figure
Page 22 and 23: 14 2 Theoretical foundation Fi
Page 25 and 26: 17 3 Experimental foundations 3.1 P
Page 27 and 28: 3.2 General setup 19 Figure 3.2: ch
Page 29 and 30: 3.4 SLS: SIS-HRPES 21 1 3 ARPES the
Page 31 and 32: 23 4 EuRh 2 Si 2 - semi-localized e
Page 33 and 34: 4.1 Overview - properties and class
Page 49 and 50: 4.2 Hybridization: localized versus
Page 59: 4.2 Hybridization: localized versus
Page 63: 4.3 Perspective: quasi-linear dispe
Page 66 and 67: 58 5 Summary to the f-d interaction
Page 68 and 69: 60 Bibliography [13] B. Kramer. A P
Page 70 and 71: 62 Bibliography [44] T. M. Rice and
Page 72 and 73: 64 Bibliography [75] Hari C. Manoha
Page 75: List of Tables 67 List of Tables 2.
Page 79: Erklärung Hiermit versichere ich,
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Diploma - Max Planck Institute for Solid State Research

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