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Bi₂Sr₂CaCu₂O₈+δ

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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 Apr 2012

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 ...


Raising Bi-O Bands Above The Fermi Energy Level Of Hole-Doped Bi₂Sr₂Cacu₂O₈+Δ And Other Cuprate Superconductors, Hsin Lin, S. Sahrakorpi, R. S. Markiewicz, A. Bansil Apr 2012

Raising Bi-O Bands Above The Fermi Energy Level Of Hole-Doped Bi₂Sr₂Cacu₂O₈+Δ And Other Cuprate Superconductors, Hsin Lin, S. Sahrakorpi, R. S. Markiewicz, A. Bansil

Robert Markiewicz

The Fermi surface (FS) of Bi₂Sr₂CaCu₂O₈₊δ (Bi2212) predicted by band theory displays Bi-related pockets around the (π,0) point, which have never been observed experimentally. We show that when the effects of hole doping either by substituting Pb for Bi or by adding excess O in Bi2212 are included, the Bi-O bands are lifted above the Fermi energy (EF) and the resulting first-principles FS is in remarkable accord with measurements. With decreasing hole doping the Bi-O bands drop below EF and the system self-dopes below a critical hole concentration. Computations on other Bi- as well as Tl- and Hg-based ...


Bilayer Splitting And Coherence Effects In Optimal And Underdoped Bi₂Sr₂Cacu₂O₈+Δ, Y. D. Chuang, A. D. Gromko, A. V. Fedorov, Y. Aiura, K. Oka, Yoichi Ando, M. Lindroos, R. S. Markiewicz, A. Bansil, D. S. Dessau Apr 2012

Bilayer Splitting And Coherence Effects In Optimal And Underdoped Bi₂Sr₂Cacu₂O₈+Δ, Y. D. Chuang, A. D. Gromko, A. V. Fedorov, Y. Aiura, K. Oka, Yoichi Ando, M. Lindroos, R. S. Markiewicz, A. Bansil, D. S. Dessau

Robert Markiewicz

We have carried out extensive high-resolution angle-resolved photoemission (ARPES) experiments on Bi₂Sr₂CACu₂O₈₊δ samples, covering the entire doping range from the overdoped to the optimally and underdoped regimes in the normal state. Our focus is on delineating the doping dependence of the bilayer splitting which is associated with the intracell coupling of electrons between the two CuO₂ planes. We exploit the photon energy of 47 eV, where strong ARPES matrix element effects are found to provide a tremendous enhancement of the antibonding to bonding component of the bilayer split bands near (π,0), in good agreement with the predictions of ...


Effect Of Orbital Symmetry Of The Tip On Scanning Tunneling Spectra Of Bi₂Sr₂Cacu₂O₈+Δ, Ilpo Suominen, Jouko Nieminen, R. S. Markiewicz, A. Bansil Apr 2012

Effect Of Orbital Symmetry Of The Tip On Scanning Tunneling Spectra Of Bi₂Sr₂Cacu₂O₈+Δ, Ilpo Suominen, Jouko Nieminen, R. S. Markiewicz, A. Bansil

Robert Markiewicz

We discuss how variations in the scanning tunneling microscope (STM) tip, whether unintentional or intentional, can lead to changes in topographic images and dI/dV spectra. We consider the possibility of utilizing functionalized tips in order to improve the sensitivity of STM experiments to local irregularities at the surface or hidden below the surface layers. The change in the tip symmetry can radically alter the contrast of the topographic image due to changes in tip-surface overlap. The dI/dV curves change their shape according to which sample bands the tip orbital tends to overlap. In addition, relative phases between competing ...


Induced Superconductivity In Noncuprate Layers Of The Bi₂Sr₂Cacu₂O₈+Δ High-Temperature Superconductor: Modeling Of Scanning Tunneling Spectra, Ilpo Suominen, Jouko Nieminen, R. Markiewicz, A. Bansil Apr 2012

Induced Superconductivity In Noncuprate Layers Of The Bi₂Sr₂Cacu₂O₈+Δ High-Temperature Superconductor: Modeling Of Scanning Tunneling Spectra, Ilpo Suominen, Jouko Nieminen, R. Markiewicz, A. Bansil

Robert Markiewicz

We analyze how the coherence peaks observed in scanning tunneling spectroscopy (STS) of cuprate high-temperature superconductors are transferred from the cuprate layer to the oxide layers adjacent to the STS microscope tip. For this purpose, we have carried out a realistic multiband calculation for the superconducting state of Bi₂Sr₂CaCu₂O₈₊δ (Bi2212) assuming a short-range d-wave pairing interaction confined to the nearest-neighbor Cu dₓ2y2 orbitals. The resulting anomalous matrix elements of the Green’s function allow us to monitor how pairing is then induced not only within the cuprate bilayer but also within and across other layers and ...


Origin Of The Electron-Hole Asymmetry In The Scanning Tunneling Spectrum Of The High-Temperature Bi₂Sr₂Cacu₂O₈+Δ Superconductor, Jouko Nieminen, Hsin Lin, R. Markiewicz, A. Bansil Apr 2012

Origin Of The Electron-Hole Asymmetry In The Scanning Tunneling Spectrum Of The High-Temperature Bi₂Sr₂Cacu₂O₈+Δ Superconductor, Jouko Nieminen, Hsin Lin, R. Markiewicz, A. Bansil

Robert Markiewicz

We have developed a material specific theoretical framework for modeling scanning tunneling spectroscopy (STS) of high-temperature superconducting materials in the normal as well as the superconducting state. Results for Bi₂Sr₂CaCu₂O₈₊δ (Bi2212) show clearly that the tunneling process strongly modifies the STS spectrum from the local density of states of the dₓ2₋y2 orbital of Cu. The dominant tunneling channel to the surface Bi involves the dₓ2₋y2 orbitals of the four neighboring Cu atoms. In accord with experimental observations, the computed spectrum displays a remarkable asymmetry between the processes of electron injection and extraction, which arises from contributions of ...


Raising Bi-O Bands Above The Fermi Energy Level Of Hole-Doped Bi₂Sr₂Cacu₂O₈+Δ And Other Cuprate Superconductors, Hsin Lin, S. Sahrakorpi, R. S. Markiewicz, A. Bansil Apr 2012

Raising Bi-O Bands Above The Fermi Energy Level Of Hole-Doped Bi₂Sr₂Cacu₂O₈+Δ And Other Cuprate Superconductors, Hsin Lin, S. Sahrakorpi, R. S. Markiewicz, A. Bansil

Hsin Lin

The Fermi surface (FS) of Bi₂Sr₂CaCu₂O₈₊δ (Bi2212) predicted by band theory displays Bi-related pockets around the (π,0) point, which have never been observed experimentally. We show that when the effects of hole doping either by substituting Pb for Bi or by adding excess O in Bi2212 are included, the Bi-O bands are lifted above the Fermi energy (EF) and the resulting first-principles FS is in remarkable accord with measurements. With decreasing hole doping the Bi-O bands drop below EF and the system self-dopes below a critical hole concentration. Computations on other Bi- as well as Tl- and Hg-based ...


Origin Of The Electron-Hole Asymmetry In The Scanning Tunneling Spectrum Of The High-Temperature Bi₂Sr₂Cacu₂O₈+Δ Superconductor, Jouko Nieminen, Hsin Lin, R. S. Markiewicz, A. Bansil Apr 2012

Origin Of The Electron-Hole Asymmetry In The Scanning Tunneling Spectrum Of The High-Temperature Bi₂Sr₂Cacu₂O₈+Δ Superconductor, Jouko Nieminen, Hsin Lin, R. S. Markiewicz, A. Bansil

Hsin Lin

We have developed a material specific theoretical framework for modeling scanning tunneling spectroscopy (STS) of high-temperature superconducting materials in the normal as well as the superconducting state. Results for Bi₂Sr₂CaCu₂O₈₊δ (Bi2212) show clearly that the tunneling process strongly modifies the STS spectrum from the local density of states of the dₓ2₋y2 orbital of Cu. The dominant tunneling channel to the surface Bi involves the dₓ2₋y2 orbitals of the four neighboring Cu atoms. In accord with experimental observations, the computed spectrum displays a remarkable asymmetry between the processes of electron injection and extraction, which arises from contributions of ...


Raising Bi-O Bands Above The Fermi Energy Level Of Hole-Doped Bi₂Sr₂Cacu₂O₈+Δ And Other Cuprate Superconductors, Hsin Lin, S. Sahrakorpi, R. S. Markiewicz, A. Bansil Apr 2012

Raising Bi-O Bands Above The Fermi Energy Level Of Hole-Doped Bi₂Sr₂Cacu₂O₈+Δ And Other Cuprate Superconductors, Hsin Lin, S. Sahrakorpi, R. S. Markiewicz, A. Bansil

Arun Bansil

The Fermi surface (FS) of Bi₂Sr₂CaCu₂O₈₊δ (Bi2212) predicted by band theory displays Bi-related pockets around the (π,0) point, which have never been observed experimentally. We show that when the effects of hole doping either by substituting Pb for Bi or by adding excess O in Bi2212 are included, the Bi-O bands are lifted above the Fermi energy (EF) and the resulting first-principles FS is in remarkable accord with measurements. With decreasing hole doping the Bi-O bands drop below EF and the system self-dopes below a critical hole concentration. Computations on other Bi- as well as Tl- and Hg-based ...


Induced Superconductivity In Noncuprate Layers Of The Bi₂Sr₂Cacu₂O₈+Δ High-Temperature Superconductor: Modeling Of Scanning Tunneling Spectra, Ilpo Suominen, Jouko Nieminen, R. Markiewicz, A. Bansil Apr 2012

Induced Superconductivity In Noncuprate Layers Of The Bi₂Sr₂Cacu₂O₈+Δ High-Temperature Superconductor: Modeling Of Scanning Tunneling Spectra, Ilpo Suominen, Jouko Nieminen, R. Markiewicz, A. Bansil

Arun Bansil

We analyze how the coherence peaks observed in scanning tunneling spectroscopy (STS) of cuprate high-temperature superconductors are transferred from the cuprate layer to the oxide layers adjacent to the STS microscope tip. For this purpose, we have carried out a realistic multiband calculation for the superconducting state of Bi₂Sr₂CaCu₂O₈₊δ (Bi2212) assuming a short-range d-wave pairing interaction confined to the nearest-neighbor Cu dₓ2y2 orbitals. The resulting anomalous matrix elements of the Green’s function allow us to monitor how pairing is then induced not only within the cuprate bilayer but also within and across other layers and ...


Effect Of Orbital Symmetry Of The Tip On Scanning Tunneling Spectra Of Bi₂Sr₂Cacu₂O₈+Δ, Ilpo Suominen, Jouko Nieminen, R. S. Markiewicz, A. Bansil Apr 2012

Effect Of Orbital Symmetry Of The Tip On Scanning Tunneling Spectra Of Bi₂Sr₂Cacu₂O₈+Δ, Ilpo Suominen, Jouko Nieminen, R. S. Markiewicz, A. Bansil

Arun Bansil

We discuss how variations in the scanning tunneling microscope (STM) tip, whether unintentional or intentional, can lead to changes in topographic images and dI/dV spectra. We consider the possibility of utilizing functionalized tips in order to improve the sensitivity of STM experiments to local irregularities at the surface or hidden below the surface layers. The change in the tip symmetry can radically alter the contrast of the topographic image due to changes in tip-surface overlap. The dI/dV curves change their shape according to which sample bands the tip orbital tends to overlap. In addition, relative phases between competing ...


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 Apr 2012

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 ...


Origin Of The Electron-Hole Asymmetry In The Scanning Tunneling Spectrum Of The High-Temperature Bi₂Sr₂Cacu₂O₈+Δ Superconductor, Jouko Nieminen, Hsin Lin, R. S. Markiewicz, A. Bansil Apr 2012

Origin Of The Electron-Hole Asymmetry In The Scanning Tunneling Spectrum Of The High-Temperature Bi₂Sr₂Cacu₂O₈+Δ Superconductor, Jouko Nieminen, Hsin Lin, R. S. Markiewicz, A. Bansil

Arun Bansil

We have developed a material specific theoretical framework for modeling scanning tunneling spectroscopy (STS) of high-temperature superconducting materials in the normal as well as the superconducting state. Results for Bi₂Sr₂CaCu₂O₈₊δ (Bi2212) show clearly that the tunneling process strongly modifies the STS spectrum from the local density of states of the dₓ2₋y2 orbital of Cu. The dominant tunneling channel to the surface Bi involves the dₓ2₋y2 orbitals of the four neighboring Cu atoms. In accord with experimental observations, the computed spectrum displays a remarkable asymmetry between the processes of electron injection and extraction, which arises from contributions of ...


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 Apr 2012

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.