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- ARPES (13)
- Angle-resolved photoemission (10)
- Compton scattering (9)
- Cuprates (8)
- Muffin-tin alloys (7)
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- Bi₂Sr₂CaCu₂O₈+δ (6)
- Fermi energy (6)
- Electronic structure (5)
- Coherent-potential approximation (4)
- Cu (4)
- Electron momentum density (4)
- Fermi surface (4)
- La₂₋ₓSrₓCuO₄ (4)
- Strongly correlated electrons (4)
- Bi₂Sr₂CaCu₂O₈ (3)
- Compton profiles (3)
- Fermi level (3)
- Korringa-Kohn-Rostoker coherent-potential-approximation (3)
- Matrix element effects (3)
- Model Hamiltonian (3)
- Muffin-tin Hamiltonian (3)
- Nd₂₋ₓCeₓCuO₄ (3)
- Optical theorem (3)
- STM (3)
- Angle-resolved photoemission spectroscopy (2)
- Angle-resovled photoemission spectroscopy (2)
- AₓB₁₋ₓ (2)
- Bi2212 (2)
- Coherent potential (2)
- CuAl (2)
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Articles 31 - 60 of 98
Full-Text Articles in Physics
Special Directions For Brillouin-Zone Integration: Application To Density Of-States Calculations, R. Prasad, A. Bansil
Special Directions For Brillouin-Zone Integration: Application To Density Of-States Calculations, R. Prasad, A. Bansil
Arun Bansil
We present several large sets of special directions for cubic lattices. The question of accuracy obtainable in density-of-states and Fermi-energy evaluations in disordered alloys by using various direction sets is discussed. In this context, results on the simple cubic tight-binding band and on the model Hamiltonian for Cu are considered.
Reconstructing The Bulk Fermi Surface And Superconducting Gap Properties From Neutron Scattering Experiments, Tanmoy Das, R. Markiewicz, A. Bansil
Reconstructing The Bulk Fermi Surface And Superconducting Gap Properties From Neutron Scattering Experiments, Tanmoy Das, R. Markiewicz, A. Bansil
Arun Bansil
We develop an analytical tool to extract bulk electronic properties of unconventional superconductors from inelastic neutron scattering spectra. We show that the upward and downward branches of the spin excitation spectra have distinct origins, with the upper branch representing a gapped spin-wave dispersion and the lower branch associated with Bogoliubov quasiparticle scattering on the Fermi surface. Combined, they produce an "hourglass" dispersion with 45 degrees rotation of the spectrum, as found experimentally. The downward dispersion can be inverted to reveal the Fermi momentum dispersion of the single-particle spectrum as well as the corresponding superconducting (SC) gap function, analogously to the …
Resonating-Valence-Bond Ground State Of Lithium Nanoclusters, D. Nissenbaum, L. Spanu, C. Attaccalite, B. Barbiellini, A. Bansil
Resonating-Valence-Bond Ground State Of Lithium Nanoclusters, D. Nissenbaum, L. Spanu, C. Attaccalite, B. Barbiellini, A. Bansil
Arun Bansil
We have performed diffusion quantum Monte Carlo simulations of Li clusters showing that resonating-valence-bond (RVB) pairing correlations between electrons provide a substantial contribution to the cohesive energy. The RVB effects are identified in terms of electron transfers from s-like to p-like character, constituting a possible explanation for the breakdown of the Fermi-liquid picture observed in recent high-resolution Compton scattering experiments for bulk Li.
Influence Of The Third Dimension Of Quasi-Two-Dimensional Cuprate Superconductors On Angle-Resolved Photoemission Spectra, A. Bansil, M. Lindroos, S. Sahrakorpi, R. S. Markiewicz
Influence Of The Third Dimension Of Quasi-Two-Dimensional Cuprate Superconductors On Angle-Resolved Photoemission Spectra, A. Bansil, M. Lindroos, S. Sahrakorpi, R. S. Markiewicz
Arun Bansil
Angle-resolved photoemission spectroscopy (ARPES) presents significant simplifications in analyzing strictly two-dimensional (2D) materials, but even the most anisotropic physical systems display some residual three-dimensionality. Here we demonstrate how this third dimension manifests itself in ARPES spectra of quasi-2D materials by considering the example of the cuprate Bi₂Sr₂CaCu₂O₈ (Bi2212). The intercell, interlayer hopping, which is responsible for kz dispersion of the bands, is found to induce an irreducible broadening to the ARPES line shapes with a characteristic dependence on the in-plane momentum k‖. Our study suggests that ARPES line shapes can provide a direct spectroscopic window for establishing the existence of …
Spontaneous Magnetization And Electron Momentum Density In Three-Dimensional Quantum Dots, R. Saniz, B. Barbiellini, A. B. Denison, A. Bansil
Spontaneous Magnetization And Electron Momentum Density In Three-Dimensional Quantum Dots, R. Saniz, B. Barbiellini, A. B. Denison, A. Bansil
Arun Bansil
We discuss an exactly solvable model Hamiltonian for describing the interacting electron gas in a quantum dot. Results for a spherical square-well confining potential are presented. The ground state is found to exhibit striking oscillations in spin polarization with dot radius at a fixed electron density. These oscillations are shown to induce characteristic signatures in the momentum density of the electron gas, providing a route for direct experimental observation of the dot magnetization via spectroscopies sensitive to the electron momentum density.
Electronic Structure Of Cu₇₅Au₂₅ Disordered Alloy, E. Arola, R. S. Rao, A. Salokatve, A. Bansil
Electronic Structure Of Cu₇₅Au₂₅ Disordered Alloy, E. Arola, R. S. Rao, A. Salokatve, A. Bansil
Arun Bansil
We present angle-resolved uv photoemission (normal emission) measurements from the (100) and (111) surfaces of Cu₇₅Au₂₅ alloy single crystals, together with fully relativistic as well as nonrelativistic Korringa-Kohn-Rostoker coherent-potential-approximation calculations of complex energy bands and densities of states. A good overall accord is found between the measurements and theoretical predictions with regard to the shifts and smearings of various bulk states in the alloy. The characteristic effects of alloying Au on the electronic structure of Cu are identified; the principal Au-induced feature is 2.5 eV wide, and appears 3 eV below the Cu-derived d band in the alloy; this feature …
High-Resolution Compton Scattering Study Of Li: Asphericity Of The Fermi Surface And Electron Correlation Effects, Y. Sakurai, Y. Tanaka, A. Bansil, S. Kaprzyk, A. T. Stewart, Y. Nagashima, T. Hyodo, S. Nanao, H. Kawata, N. Shiotani
High-Resolution Compton Scattering Study Of Li: Asphericity Of The Fermi Surface And Electron Correlation Effects, Y. Sakurai, Y. Tanaka, A. Bansil, S. Kaprzyk, A. T. Stewart, Y. Nagashima, T. Hyodo, S. Nanao, H. Kawata, N. Shiotani
Arun Bansil
We present high-resolution Compton scattering spectra from Li single crystals together with corresponding highly accurate local-density-approximation (LDA) based computations. The data are analyzed to obtain Fermi surface radii along the three principal symmetry directions; the maximum measured anisotropy is found to be (4.6±1.0)%. Comparisons between the measured and computed spectra clearly reveal departures from the conventional one-particle LDA picture of the ground state momentum density of the electron gas. This study establishes the potential of Compton scattering as a tool for investigating Fermiology-related issues in materials.
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.
Electron Momentum Densities In Disordered Muffin-Tin Alloys, A. Bansil, R. S. Rao, P. E. Mijnarends, L. Schwartz
Electron Momentum Densities In Disordered Muffin-Tin Alloys, A. Bansil, R. S. Rao, P. E. Mijnarends, L. Schwartz
Arun Bansil
The application of average t-matrix (ATA) and coherent potential (CPA) approximations to the calculation of average electron momentum density ρ(p) in random muffin-tin alloys AₓB₁₋ₓ is considered. The necessary equations for the general matrix elements of the operators describing scattering by the CPA atom and also by an A or B atom embedded in the effective medium are derived. Various versions of the ATA for ρ(p) are discussed. Several ρ(p) curves calculated on the basis of the CPA and ATA in CuₓNi₁₋ₓ are presented. These results are used to delineate the effects on ρ(p) of self-consistency in the treatment of …
Nodeless D-Wave Superconducting Pairing Due To Residual Antiferromagnetism In Underdoped Pr2-Xcexcuo4-Δ, Tanmoy Das, R. S. Markiewicz, A. Bansil
Nodeless D-Wave Superconducting Pairing Due To Residual Antiferromagnetism In Underdoped Pr2-Xcexcuo4-Δ, Tanmoy Das, R. S. Markiewicz, A. Bansil
Arun Bansil
We investigate the doping dependence of the penetration depth versus temperature in electron-doped Pr₂₋ₓCeₓCuO4-δ using a model which assumes the uniform coexistence of (mean-field) antiferromagnetism and superconductivity. Despite the presence of a dₓ2₋y2 pairing gap in the underlying spectrum, we find nodeless behavior of the low-T penetration depth in the underdoped case, in accord with experimental results. As doping increases, a linear-in-T behavior of the penetration depth, characteristic of d-wave pairing, emerges as the lower magnetic band crosses the Fermi level and creates a nodal Fermi surface pocket.
Optical Theorem And Multiple-Scattering Theory: Electronic States In Disordered Transion-Metals, L. Schwartz, A. Bansil
Optical Theorem And Multiple-Scattering Theory: Electronic States In Disordered Transion-Metals, L. Schwartz, A. Bansil
Arun Bansil
In disordered systems, apparently reasonable decoupling procedures can lead to negative densities of electronic states near resonant d bands. By applying the optical theorem to the multiple-scattering series we can determine a prior whether a given decoupling will necessarily yield positive results. Since none of the extensions of the coherent-potential approximation to amorphous systems is found to meet this requirement, we propose a new scheme which is both self-consistent and guaranteed to give a positive spectrum.
Nonmonotonic Dₓ2₋Y2 Superconducting Gap In Electron-Doped Pr0.89lace0.11cuo4: Evidence Of Coexisting Antiferromagnetism And Superconductivity?, Tanmoy Das, R. S. Markiewicz, A. Bansil
Nonmonotonic Dₓ2₋Y2 Superconducting Gap In Electron-Doped Pr0.89lace0.11cuo4: Evidence Of Coexisting Antiferromagnetism And Superconductivity?, Tanmoy Das, R. S. Markiewicz, A. Bansil
Arun Bansil
Recent experiments on Pr0.89LaCe0.11CuO₄ observe an anisotropic spin-correlation gap and a nonmonotonic superconducting (SC) gap, which we analyze within the framework of a t-t′-t″-t‴-tiv-U model with a dₓ2−y2 pairing interaction including a third-harmonic contribution. By introducing a realistic broadening of the quasiparticle spectrum to reflect small-angle scattering, our computations explain the experimental observations, especially the presence of a maximum in the leading-edge gap in the vicinity of the hot spots. Our analysis suggests that the material behaves like a two-band superconductor with the d-wave third harmonic acting as the interband pairing gap, and that the antiferromagnetic and SC orders coexist …
Fermi Surface And Electron-Positron Momentum Density In Yba₂Cu₃O₇, A. Bansil, P. E. Mijnarends, L. C. Smedskjaer
Fermi Surface And Electron-Positron Momentum Density In Yba₂Cu₃O₇, A. Bansil, P. E. Mijnarends, L. C. Smedskjaer
Arun Bansil
By folding the local-density-approximation (LDA) band-theory-based electron-positron momentum density into the first Brillouin zone, we find that signatures from all the Fermi-surface sheets can be obtained in YBa₂Cu₃O₇, including in particular the Cu-O plane sheets. Our theoretical predictions appear to be in reasonable overall accord with the corresponding measurements by positron-annihilation two-dimensional angular correlation of annihilation radiation (2D-ACAR) of Smedskjaer et al., which have been interpreted in terms of Fermi surfaces. The Cu-O chain-related (electron) states appear to be substantially modified from LDA predictions. However, no firm conclusions concerning the existence of the Fermi surface in YBa₂Cu₃O₇ can at the …
Proposal To Determine The Fermi-Surface Topology Of A Doped Iron-Based Superconductor Using Bulk-Sensitive Fourier-Transform Compton Scattering, Yung Jui Wang, Hsin Lin, B. Barbiellini, P. E. Mijnarends, S. Kaprzyk, R. S. Markiewicz, A. Bansil
Proposal To Determine The Fermi-Surface Topology Of A Doped Iron-Based Superconductor Using Bulk-Sensitive Fourier-Transform Compton Scattering, Yung Jui Wang, Hsin Lin, B. Barbiellini, P. E. Mijnarends, S. Kaprzyk, R. S. Markiewicz, A. Bansil
Arun Bansil
We have carried out first-principles calculations of the Compton scattering spectra to demonstrate that the filling of the hole Fermi surface in LaO₁₋ₓFₓFeAs produces a distinct signature in the Fourier-transformed Compton spectrum when the momentum transfer vector lies along the [100] direction. We thus show how the critical concentration xc
Electron Momentum Density In Disordered Muffin-Tin Cu1-Xnix In The Average-T-Matrix Approximation, P. E. Mijnarends, A. Bansil
Electron Momentum Density In Disordered Muffin-Tin Cu1-Xnix In The Average-T-Matrix Approximation, P. E. Mijnarends, A. Bansil
Arun Bansil
In an earlier article we discussed the formalism for evaluating the average electron-momentum density in a random binary alloy by using the average-t-matrix approximation to treat the disorder and muffin-tin potentials to represent the constituent atoms. The present paper considers the application of this formalism to Cu₁₋ₓNiₓ over a range of alloy compositions. The characteristic effects of disorder on the spectral momentum density 〈ρ(p,E)〉 are delineated. In discussing the momentum density 〈ρ(p)〉 we focus on how this quantity changes as x increases from 0 to 1 and the Ni d band develops from a virtual bound state below the Fermi …
Topological Electronic Structure In Half-Heusler Topological Insulators, W. Al-Sawai, Hsin Lin, R. Markiewicz, L. Wray, Y. Xia, S. Xu, M. Hasan, A. Bansil
Topological Electronic Structure In Half-Heusler Topological Insulators, W. Al-Sawai, Hsin Lin, R. Markiewicz, L. Wray, Y. Xia, S. Xu, M. Hasan, A. Bansil
Arun Bansil
We have investigated band structures of a series of 28 ternary half-Heusler compounds MM'X of MgAgAs type, where M=(Lu, La, Sc, Y) and M'X=(PtBi, AuPb, PdBi, PtSb, AuSn, NiBi, PdSb). Our results show that the Z₂ topological order is due to a single band inversion at the Γ point. In native states, these half-Heusler compounds are identified as being topologically nontrivial semimetals, or nontrivial metals, or trivial insulators, which can be turned into insulating thin films on suitable substrates. Our analysis reveals a straightforward relationship which connects the band inversion strength (extent of deviation from the critical point) to the …
Surface States And Angle-Resolved Photoemission Spectra From Nd₂₋ₓceₓcuo₄, M. Lindroos, A. Bansil
Surface States And Angle-Resolved Photoemission Spectra From Nd₂₋ₓceₓcuo₄, M. Lindroos, A. Bansil
Arun Bansil
By carrying out first-principles angle-resolved photoemission (ARPES) computations within the local-density-approximation-based band theory framework, we predict the existence of surface states on the (001) surface of the superconductor Nd₂₋ₓCeₓCuO₄ (NCCO). Two surface state bands are identified in the vicinity of the Fermi energy. The associated states possess quite different characteristics in terms of their binding energy, dispersion with k∥, and the polarization and photon energy dependence. Our theoretical predictions offer new insight into the existing ARPES data on NCCO with which they are consistent.
Energy Dependence Of Experimental Be Compton Profiles, S. Huotari, K. Hamalainen, S. Manninen, S. Kaprzyk, A. Bansil, W. Caliebe, T. Buslaps, V. Honkimaki, P. Suortti
Energy Dependence Of Experimental Be Compton Profiles, S. Huotari, K. Hamalainen, S. Manninen, S. Kaprzyk, A. Bansil, W. Caliebe, T. Buslaps, V. Honkimaki, P. Suortti
Arun Bansil
High-resolution Compton scattering measurements on Be single crystals along three main crystallographic directions ([10.0], [11.0], and [00.1]) have been carried out using incident photon energies of 10, 29, and 56 keV to study the energy dependence of the scattering cross:section. The experimental Compton profiles are in good agreement with theoretical profiles employing the local density approximation-based band theory framework. Extensive comparisons between the computed and measured profiles, their first derivatives, and anisotropies defined as differences between various pairs of profiles show an excellent level of accord. The details related to the Fermi surface are clearly seen in the experimental Compton …
Observation Of A Tamm-Type State On Cu0.9al0.1(100) Surface: Disorder Effects And Bulk Electronic Structure Of An Alloy, M. Pessa, H. Asonen, R. S. Rao, R. Prasad, A. Bansil
Observation Of A Tamm-Type State On Cu0.9al0.1(100) Surface: Disorder Effects And Bulk Electronic Structure Of An Alloy, M. Pessa, H. Asonen, R. S. Rao, R. Prasad, A. Bansil
Arun Bansil
The electronic structure of a CU0.9Al0.1(100) single crystal has been studied with use of an angle-resolved photoemission technique. An intrinsic Tamm-type surface state is found to exist in the disordered alloy. The linewidth of the surface state is analyzed to deduce the disorder-induced smearing of energy levels. These and other experimental results are discussed in terms of the computed band structure of the alloy on the basis of coherent-potential approximation applied to a realistic muffin-tin Hamiltonian.
High Resolution Compton Scattering Study Of Be, K. Hamalainen, S. Manninen, C. C. Kao, W. Caliebe, J. B. Hastings, A. Bansil, S. Kaprzyk, P. M. Platzman
High Resolution Compton Scattering Study Of Be, K. Hamalainen, S. Manninen, C. C. Kao, W. Caliebe, J. B. Hastings, A. Bansil, S. Kaprzyk, P. M. Platzman
Arun Bansil
We have carried out high-resolution Compton scattering measurements from two single crystals of Be ([00.1] and [11.0]), together with highly accurate all-electron first-principles computations of the profiles within the band theory framework. The Compton data were collected using a newly constructed crystal spectrometer at a record momentum resolution varying between 0.023 and 0.032 a.u. (full width at half maximum) with 8 keV x rays from a synchrotron source. Although the overall shapes of the measured and computed spectra are in good accord, the fine structure in the data shows significant discrepancies with respect to the local density approximation based theoretical …
High-Resolution Angle-Resolved Photoemission Spectra From Ni(100): Matrix Element Effects And Spin-Resolved Initial And Final State Bands, S. Sahrakorpi, M. Lindroos, A. Bansil
High-Resolution Angle-Resolved Photoemission Spectra From Ni(100): Matrix Element Effects And Spin-Resolved Initial And Final State Bands, S. Sahrakorpi, M. Lindroos, A. Bansil
Arun Bansil
We have carried out extensive one- and three-step angle-resolved photoemission spectroscopy (ARPES) intensity computations on Ni(100) within the band theory framework based on the local spin-density approximation. The results show a good overall level of accord with the recent high-resolution ARPES experiments on Ni(100) which probe the majority- and minority-spin Σ₁ band along the Γ-K direction near the Fermi energy (EF), uncertainties inherent in our first-principles approach notwithstanding. The k‖ and energy dependencies of various spectral features are delineated in terms of the interplay between changes in the initial- and final-state bands and the associated transition matrix elements. The remarkable …
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
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 energy and polarization …
Role Of Oxygen Electrons In The Metal-Insulator Transition In The Magnetoresistive Oxide La2-2xsr1+2xmn2o7 Probed By Compton Scattering, B. Barbiellini, A. Koizumi, P. E. Mijnarends, W. Al-Sawai, Hsin Lin, T. Nagao, K. Hirota, M. Itou, Y. Sakurai, A. Bansil
Role Of Oxygen Electrons In The Metal-Insulator Transition In The Magnetoresistive Oxide La2-2xsr1+2xmn2o7 Probed By Compton Scattering, B. Barbiellini, A. Koizumi, P. E. Mijnarends, W. Al-Sawai, Hsin Lin, T. Nagao, K. Hirota, M. Itou, Y. Sakurai, A. Bansil
Arun Bansil
We have studied the [100]-[110] anisotropy of the Compton profile in the bilayer manganite. Quantitative agreement is found between theory and experiment with respect to the anisotropy in the two metallic phases (i.e., the low temperature ferromagnetic and the colossal magnetoresistant phase under a magnetic field of 7 T). Robust signatures of the metal-insulator transition are identified in the momentum density for the paramagnetic phase above the Curie temperature. We interpret our results as providing direct evidence for the transition from the metalliclike to the admixed ionic-covalent bonding accompanying the magnetic transition. The number of electrons involved in this phase …
Systematic Doping Evolution Of The Underlying Fermi Surface Of La₂₋ₓsrₓcuo₄, T. Yoshida, X. J. Zhou, K. Tanaka, W. L. Yang, Z. Hussain, Z. X. Shen, A. Fujimori, S. Sahrakorpi, M. Lindroos, R. S. Markiewicz, A. Bansil, Seiki Komiya, Yoichi Ando, H. Eisaki, T. Kakeshita, S. Uchida
Systematic Doping Evolution Of The Underlying Fermi Surface Of La₂₋ₓsrₓcuo₄, T. Yoshida, X. J. Zhou, K. Tanaka, W. L. Yang, Z. Hussain, Z. X. Shen, A. Fujimori, S. Sahrakorpi, M. Lindroos, R. S. Markiewicz, A. Bansil, Seiki Komiya, Yoichi Ando, H. Eisaki, T. Kakeshita, S. Uchida
Arun Bansil
We have performed a systematic doping-dependent study of La₂₋ₓSrₓCuO₄ (LSCO) (0.03 <= x <= 0.3) by angle-resolved photoemWe have performed a systematic doping-dependent study of La₂₋ₓSrxCuO₄ (LSCO) (0.03⩽x⩽0.3) by angle-resolved photoemission spectroscopy. Over this entire doping range, the underlying “Fermi surface” determined from the low-energy spectral weight approximately satisfies Luttinger’s theorem, even down to the lightly doped region. This is in strong contrast to the results on Ca₂₋ₓNaₓCuO₂Cl₂ (Na-CCOC), which show a clear deviation from Luttinger’s theorem. We correlate these differences between LSCO and Na-CCOC with differences in the behavior of chemical potential shift and spectral weight transfer induced by …
Optical Theorem And Multiple-Scattering Theory: Electronic States In Substitutional Alloys, L. Schwartz, A. Bansil
Optical Theorem And Multiple-Scattering Theory: Electronic States In Substitutional Alloys, L. Schwartz, A. Bansil
Arun Bansil
When multiple-scattering theory is used to describe the electronic properties of disordered transition-metal systems, decoupling procedures which appear to be physically reasonable can lead to negative densities of states in the vicinity of the resonant d bands. We present a method, based on the application of the optical theorem to the total scattering operator, that allows us to determine a priori which approximation schemes can be relied upon to produce a positive spectrum. The application of this method to substitutionally disordered binary alloys is discussed here. We find that both the average-t-matrix and coherent-potential approximations will always yield nonnegative densities …
Renormalization Of F Levels Away From The Fermi Energy In Electron Excitation Spectroscopies: Density-Functional Results For Nd2-Xcexcuo4, T. Jarlborg, B. Barbiellini, H. Lin, R. S. Markiewicz, A. Bansil
Renormalization Of F Levels Away From The Fermi Energy In Electron Excitation Spectroscopies: Density-Functional Results For Nd2-Xcexcuo4, T. Jarlborg, B. Barbiellini, H. Lin, R. S. Markiewicz, A. Bansil
Arun Bansil
Relaxation energies for photoemission where an occupied electronic state is excited and for inverse photoemission where an empty state is filled are calculated within the density-functional theory with application to Nd₂₋ₓCeₓCuO₄. The associated relaxation energies are obtained by computing differences in total energies between the ground state and an excited state in which one hole or one electron is added into the system. The relaxation energies of f electrons are found to be of the order of several eV’s, indicating that f bands will appear substantially away from the Fermi energy (EF) in their spectroscopic images, even if these bands …
Effective-Medium Theory Of Electronic States In Structurally Disordered Metals: Application To Liquid Cu, L. Huisman, D. Nicholson, L. Schwartz, A. Bansil
Effective-Medium Theory Of Electronic States In Structurally Disordered Metals: Application To Liquid Cu, L. Huisman, D. Nicholson, L. Schwartz, A. Bansil
Arun Bansil
We consider the application of the effective-medium approximation (EMA) to the muffin-tin model of a liquid metal. The spherical symmetry of the average liquid is used to reduce the momentum (k)-dependent self-consistency requirements of the theory to a form in which they involve one-dimensional rather than three-dimensional integrations. We also show that, within the EMA, a closed expression for the integrated density of states can be derived, and that this expression provides a useful check on the convergence of the self-consistent equations. The theory is applied to liquid Cu. The self-consistent equations converge without difficulty and the resulting electronic spectrum …
Magnetic Mechanism Of Quasiparticle Pairing In Hole-Doped Cuprate Superconductors, R. S. Markiewicz, A. Bansil
Magnetic Mechanism Of Quasiparticle Pairing In Hole-Doped Cuprate Superconductors, R. S. Markiewicz, A. Bansil
Arun Bansil
We have computed α2F’s for the hole-doped cuprates within the framework of the one-band Hubbard model, where the full magnetic response of the system is treated properly. The d-wave pairing weight α2Fd is found not only to contain a low-energy peak due to excitations near (π,π) expected from neutron-scattering data but also to display substantial spectral weight at higher energies due to contributions from other parts of the Brillouin zone as well as pair-breaking ferromagnetic excitations at low energies. The resulting solutions of the Eliashberg equations yield transition temperatures and gaps comparable to the experimentally observed values, suggesting that magnetic …
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
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 reveals an important electron-phonon many-body …