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## Full-Text Articles in Physics

Electronic Structure Of The Metallic Ground State Of La2−2xsr1+2xmn2o7 For X≈0.59 And Comparison With X=0.36,0.38 Compounds As Revealed By Angle-Resolved Photoemission, Z. Sun, J. F. Douglas, Q. Wang, D. S. Dessau, A. V. Fedorov, H. Lin, S. Sahrakorpi, B. Barbiellini, R. S. Markiewicz, A. Bansil, H. Zheng, J. F. Mitchell

#### Electronic Structure Of The Metallic Ground State Of La2−2xsr1+2xmn2o7 For X≈0.59 And Comparison With X=0.36,0.38 Compounds As Revealed By Angle-Resolved Photoemission, Z. Sun, J. F. Douglas, Q. Wang, D. S. Dessau, A. V. Fedorov, H. Lin, S. Sahrakorpi, B. Barbiellini, R. S. Markiewicz, A. Bansil, H. Zheng, J. F. Mitchell

*Bernardo Barbiellini*

Using angle-resolved photoemission spectroscopy, we present the electronic structure of the metallic ground state of La₂₋₂ₓSr₁₊₂ₓMn₂O₇ (x≈0.59) and interpret the results in terms of first-principles band-structure computations, of which the generalized gradient approximation yields the best agreement with the experimental data. No bilayer-split bands are found in this compound, indicating the near degeneracy of electronic states in the neighboring MnO₂ layers due to its A-type antiferromagnetic structure. The d₃z2₋r2 states near the zone center were not observed, which is also consistent with its A-type antiferromagnetic structure. Near the Fermi level, a kink in the dispersion ...

Emergence Of Multiple Fermi Surface Maps In Angle-Resolved Photoemission From Bi₂Sr₂Cacu₂O₈+Δ, M. C. Asensio, J. Avila, L. Roca, A. Tejeda, G. D. Gu, M. Lindroos, R. S. Markiewicz, A. Bansil

#### Emergence Of Multiple Fermi Surface Maps In Angle-Resolved Photoemission From Bi₂Sr₂Cacu₂O₈+Δ, M. C. Asensio, J. Avila, L. Roca, A. Tejeda, G. D. Gu, M. Lindroos, R. S. Markiewicz, A. Bansil

*Robert Markiewicz*

We report angle-resolved photoemission spectra (ARPES) for emission from the Fermi energy (EF) over a large area of the (kx,ky) plane using 21.2 and 32 eV photon energies in two distinct polarizations from an optimally doped single crystal of Bi₂Sr₂CaCu₂O₈₊δ (Bi2212), together with extensive first-principles simulations of the ARPES intensities. The results display a wide-ranging level of accord between theory and experiment, demonstrating that the ARPES matrix elements can produce a striking variety of Fermi surface maps, especially in the presence of secondary features arising from modulations of the underlying tetragonal system. Our analysis demonstrates how the ...

Evolution Of Midgap States And Residual Three Dimensionality In La₂₋ₓSrₓCuo₄, S. Sahrakorpi, M. Lindroos, R. Markiewicz, A. Bansil

#### Evolution Of Midgap States And Residual Three Dimensionality In La₂₋ₓSrₓCuo₄, S. Sahrakorpi, M. Lindroos, R. Markiewicz, A. Bansil

*Robert Markiewicz*

We carry out extensive first-principles doping-dependent computations of angle-resolved photoemission (ARPES) intensities in La₂₋ₓSrₓCuO₄ over a wide range of binding energies. Intercell hopping and the associated three dimensionality, which is usually neglected in discussing cuprate physics, is shown to play a key role in shaping the ARPES spectra. Despite the obvious importance of strong coupling effects (e.g., the presence of a lower Hubbard band coexisting with midgap states in the doped insulator), a number of salient features of the experimental ARPES spectra are captured to a surprising extent when kz dispersion is properly included in the analysis.

Special Photon Energies For Extracting The Bosonic Spectral Function Mediating Superconductivity In Bi₂Sr₂Cacu₂O₈ Via Angle-Resolved Photoemission Spectroscopy, M. Lindroos, R. S. Markiewicz, A. Bansil

#### Special Photon Energies For Extracting The Bosonic Spectral Function Mediating Superconductivity In Bi₂Sr₂Cacu₂O₈ Via Angle-Resolved Photoemission Spectroscopy, M. Lindroos, R. S. Markiewicz, A. Bansil

*Robert Markiewicz*

We delineate the complex nature of the angle-resolved photoemission spectroscopy (ARPES) matrix element in Bi₂Sr₂CaCu₂O₈ and identify photon energies where the matrix element is insensitive to wave vector and/or frequency. These special photon energies provide a unique route for extracting the spectral function of the bosonic glue mediating superconductivity and for obtaining self-energies more generally via ARPES experiments.

Site-Selectivity Properties Of The Angle-Resolved Photoemission Matrix Element In Bi₂Sr₂Cacu₂O₈, S. Sahrakorpi, M. Lindroos, A. Bansil

#### Site-Selectivity Properties Of The Angle-Resolved Photoemission Matrix Element In Bi₂Sr₂Cacu₂O₈, S. Sahrakorpi, M. Lindroos, A. Bansil

*Arun Bansil*

We show that the angle-resolved photoemission (ARPES) spectra for emission from the bonding as well as the antibonding Fermi-surface sheet in Bi₂Sr₂CaCu₂O₈ possess remarkable site, selectivity properties, in that the emission for photon energies less than 25 eV is dominated by pd excitations from just the O sites in the CuO₂ planes. There is little contribution from Cu electrons to the ARPES intensity, even though the initial states at the Fermi energy contain an admixture of Cu-d and O-p electrons. We analyze the origin of this effect by considering the nature of the associated dipole matrix element in detail and ...

Angle-Resolved Photoemission-Study Of (100), (110), And (111) Surfaces Of Cu0.9a10.1: Bulk And Surface Electronic-Structure Of The Alloy, H. Asonen, M. Lindroos, M. Pessa, P. Prasad, R. Rao, A. Bansil

#### Angle-Resolved Photoemission-Study Of (100), (110), And (111) Surfaces Of Cu0.9a10.1: Bulk And Surface Electronic-Structure Of The Alloy, H. Asonen, M. Lindroos, M. Pessa, P. Prasad, R. Rao, A. Bansil

*Arun Bansil*

We present angle-resolved photoemission spectra from the low-index faces of CuAl single crystals using 16.85- and 21.22-eV radiation, together with the computed bulk electronic structure of the alloy within the framework of the muffin-tin coherent-potential approximation (CPA). The d-band complex of Cu is found to suffer shifts of less than 0.1 eV on alloying, whereas the states of s-p symmetry are lowered in energy by as much as on the order of 1 eV. The dispersion curve of the uppermost valence band is measured and with the extrapolation of this curve to the Fermi energy (EF), the ...

Angle-Resolved Photoemission Spectra, Electronic Structure, And Spin-Dependent Scattering In Ni1-Xfex Permalloys, P. E. Mijnarends, S. Sahrakorpi, M. Lindroos, A. Bansil

#### Angle-Resolved Photoemission Spectra, Electronic Structure, And Spin-Dependent Scattering In Ni1-Xfex Permalloys, P. E. Mijnarends, S. Sahrakorpi, M. Lindroos, A. Bansil

*Arun Bansil*

We present the all-electron charge and spin self-consistent electronic structure of Ni₁₋ₓFeₓ Permalloys for a range of Fe concentrations. using the first-principles Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) scheme to treat disorder and the local spin density approximation to incorporate exchange-correlation effects. Recent high-resolution angle-resolved photoemission spectroscopy (ARPES) experiments on Ni0.90Fe0.10 and Ni0.80Fe0.20 Permalloys are analyzed in terms of the spectral density function, ABkⅡ, k⊥ = 0, EF), computed from the KKR-CPA Green function for kⅡ values varying along the Γ-K direction in the Brillouin zone. The widths of the majority as well as the minority spin ...

Electronic-Structure Of Copper-Rich Copper-Gold Alloys, H. Asonen, C. J. Barnes, M. Pessa, R. S. Rao, A. Bansil

#### Electronic-Structure Of Copper-Rich Copper-Gold Alloys, H. Asonen, C. J. Barnes, M. Pessa, R. S. Rao, A. Bansil

*Arun Bansil*

We present and discuss angle-resolved photoemission measurements from the (111) and (100) faces of CuAu single crystals containing 10 at. % Au in the bulk, together with computations of complex-energy bands and densities of states in the Cu₉₀Au₁₀ random alloy. Our calculations permit a good understanding of the shifts and smearings in the spectrum of Cu arising from the addition of Au with respect to the Cu d-band complex, the (111) Shockley state, and the (100) Tamm state. The observed position and width of the Au-induced structure in the density of states is also in good accord with the theoretical result ...

Evolution Of Midgap States And Residual Three Dimensionality In La₂₋ₓSrₓCuo₄, S. Sahrakorpi, M. Lindroos, R. S. Markiewicz, A. Bansil

#### Evolution Of Midgap States And Residual Three Dimensionality In La₂₋ₓSrₓCuo₄, S. Sahrakorpi, M. Lindroos, R. S. Markiewicz, A. Bansil

*Arun Bansil*

We carry out extensive first-principles doping-dependent computations of angle-resolved photoemission (ARPES) intensities in La₂₋ₓSrₓCuO₄ over a wide range of binding energies. Intercell hopping and the associated three dimensionality, which is usually neglected in discussing cuprate physics, is shown to play a key role in shaping the ARPES spectra. Despite the obvious importance of strong coupling effects (e.g., the presence of a lower Hubbard band coexisting with midgap states in the doped insulator), a number of salient features of the experimental ARPES spectra are captured to a surprising extent when kz dispersion is properly included in the analysis.

Electronic Structure Of Au70pd30 Disordered Alloy, E. Arola, C. J. Barnes, R. S. Rao, A. Bansil

#### Electronic Structure Of Au70pd30 Disordered Alloy, E. Arola, C. J. Barnes, R. S. Rao, A. Bansil

*Arun Bansil*

We present angle-resolved photoemission (normal-emission) measurements from the (100) surface of a disordered Au₇₀Pd₃₀ alloy single crystal using He i, Ne i, He ii, and Ne ii excitations. The experimental results are interpreted via fully relativistic Korringa-Kohn-Rostoker coherent-potential-approximation computations of complex-energy bands, spectral densities, and total and site-decomposed densities of states in the alloy. Our measurements and calculations indicate that the main effects of adding Pd to Au are the following: (i) the appearance of a Pd-derived d-band complex with small dispersion, distinctly above the Au d-band edge, centered about 1 eV below the Fermi energy, (ii) the Au-derived d-band ...

Emergence Of Multiple Fermi Surface Maps In Angle-Resolved Photoemission From Bi₂Sr₂Cacu₂O₈+Δ, M. C. Asensio, J. Avila, L. Roca, A. Tejeda, G. D. Gu, M. Lindroos, R. S. Markiewicz, A. Bansil

*Arun Bansil*

We report angle-resolved photoemission spectra (ARPES) for emission from the Fermi energy (EF) over a large area of the (kx,ky) plane using 21.2 and 32 eV photon energies in two distinct polarizations from an optimally doped single crystal of Bi₂Sr₂CaCu₂O₈₊δ (Bi2212), together with extensive first-principles simulations of the ARPES intensities. The results display a wide-ranging level of accord between theory and experiment, demonstrating that the ARPES matrix elements can produce a striking variety of Fermi surface maps, especially in the presence of secondary features arising from modulations of the underlying tetragonal system. Our analysis demonstrates how the ...

Electronic Structure Of The Metallic Ground State Of La2−2xsr1+2xmn2o7 For X≈0.59 And Comparison With X=0.36,0.38 Compounds As Revealed By Angle-Resolved Photoemission, Z. Sun, J. F. Douglas, Q. Wang, D. S. Dessau, A. V. Fedorov, H. Lin, S. Sahrakorpi, B. Barbiellini, R. S. Markiewicz, A. Bansil, H. Zheng, J. F. Mitchell

*Arun Bansil*

Using angle-resolved photoemission spectroscopy, we present the electronic structure of the metallic ground state of La₂₋₂ₓSr₁₊₂ₓMn₂O₇ (x≈0.59) and interpret the results in terms of first-principles band-structure computations, of which the generalized gradient approximation yields the best agreement with the experimental data. No bilayer-split bands are found in this compound, indicating the near degeneracy of electronic states in the neighboring MnO₂ layers due to its A-type antiferromagnetic structure. The d₃z2₋r2 states near the zone center were not observed, which is also consistent with its A-type antiferromagnetic structure. Near the Fermi level, a kink in the dispersion ...

Special Photon Energies For Extracting The Bosonic Spectral Function Mediating Superconductivity In Bi₂Sr₂Cacu₂O₈ Via Angle-Resolved Photoemission Spectroscopy, M. Lindroos, R. S. Markiewicz, A. Bansil

*Arun Bansil*

We delineate the complex nature of the angle-resolved photoemission spectroscopy (ARPES) matrix element in Bi₂Sr₂CaCu₂O₈ and identify photon energies where the matrix element is insensitive to wave vector and/or frequency. These special photon energies provide a unique route for extracting the spectral function of the bosonic glue mediating superconductivity and for obtaining self-energies more generally via ARPES experiments.

Circular Dichroism In The Angle-Resolved Photoemission Spectrum Of The High-Temperature Bi₂Sr₂Cacu₂O₈+Δ Superconductor: Can These Measurements Be Interpreted As Evidence For Time-Reversal Symmetry Breaking?, V. Arpiainen, A. Bansil, M. Lindroos

#### Circular Dichroism In The Angle-Resolved Photoemission Spectrum Of The High-Temperature Bi₂Sr₂Cacu₂O₈+Δ Superconductor: Can These Measurements Be Interpreted As Evidence For Time-Reversal Symmetry Breaking?, V. Arpiainen, A. Bansil, M. Lindroos

*Arun Bansil*

We report first-principles computations of the angle-resolved photoemission response with circularly polarized light in Bi₂Sr₂CaCu₂O₈₊δ for the purpose of delineating contributions to the circular dichroism resulting from distortions and modulations of the crystal lattice. Comparison with available experimental results shows that the measured circular dichroism from antinodal mirror planes is reproduced in quantitative detail in calculations employing the average orthorhombic crystal structure. We thus conclude that the existing angle-resolved photoemission measurements can be understood essentially within the framework of the conventional picture, without the need to invoke unconventional mechanisms.