A. D. Gromko

Doubling of the Bands in Overdoped Bi2Sr2CaCu2O8 + delta: Evidence for c-Axis Bilayer Coupling

We present high resolution angle resolved photoemission data of the bilayer superconductor Bi(2)Sr(2)CaCu(2)O(8+delta) (Bi2212) showing a clear doubling of the near E(F) bands. This splitting approaches zero along the (0,0)-->(pi,pi) nodal line and is not observed in single layer Bi(2)Sr(2)CuO(6+delta) (Bi2201), indicating that the splitting is due to the long sought after bilayer splitting effect. The splitting has a magnitude of approximately 75 meV near the middle of the zone, extrapolating to about 110 meV near the (pi,0) point. The existence of these two bands also helps to clear up the recent controversy concerning the topology of the Fermi surface.

Electronic structure of CMR oxides: High Resolution electron-spectroscopic studies and a pseudogap

Abstract We review our measurements of the electronic structure of the CMR oxides, with special emphasis on high resolution ARPES studies of the Fermi surface and near- E F states of the layered materials. While the data show many similarities to band theory predictions, there are also critical differences, in particular there being a spectral depletion or pseudogap at E F . This pseudogap is strongly temperature dependent, with major changes at the sample’s T c . These changes correlate so well with the observed resistive trends that the pseudogap should be considered as a key mechanism cooperating with double-exchange to produce the metal-insulator transition and the CMR effect. We argue that the pseudogap likely originates from strongly fluctuating charge/orbital ordering tendencies.

Copper oxide superconductors: Sharp-mode coupling in high-T c superconductors

Arising from: J. Hwang, T. Timusk & G. D. Gu Nature427, 714–717 (2004); Hwang et al. reply In conventional superconductivity, sharp phonon modes (oscillations in the crystal lattice) are exchanged between electrons within a Cooper pair, enabling superconductivity. A critical question in the study of copper oxides with high critical transition temperature (Tc) is whether such sharp modes (which may be more general, including, for example, magnetic oscillations) also play a critical role in the pairing and hence the superconductivity. Hwang et al. report evidence that sharp modes (either phononic or magnetic in origin) are not important for superconductivity in these materials1, but we show here that their conclusions are undermined by the insensitivity of their experiment to a crucial physical effect2,3,4,5,6,7.

Fermi surface topology of Bi2Sr2CaCu2O8+δ at hv = 33eV

Abstract We present Angle-Resolved Photoemission experiments (ARPES) results on Bi 2 Sr 2 CaCu 2 O 8+ δ (BSCCO) crystals. With high energy and momentum resolution, we identify the existence of electron-like portions of Fermi Surface (FS) near M at hv = 33eV . This phenomena contrasts with the hole-like topology obtained using hv ≈ 22 eV .

A RE-EXAMINATION OF THE ELECTRONIC STRUCTURE AND FERMI SURFACE OF BSCCO

We have performed angle-resolved photoemission (ARPES) experiments on a variety of Bi-Sr-Ca-Cu-O (BSCCO) samples. By applying a stricter set of FS crossing criteria as well as by varying the incident photon energy outside the usual range, we have found very different behavior from that previously observed. Instead of being centered around the X or Y points and having hole-like character, we argue that the FS is centered around the Γ point and contains electron-like portions. In addition, the flat bands just below EF around are not observed at the photon energy of 33eV, raising questions about the origin of these states.

Doubling of the Bands in Overdoped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O

We present high resolution angle resolved photoemission data of the bilayer superconductor Bi(2)Sr(2)CaCu(2)O(8+delta) (Bi2212) showing a clear doubling of the near E(F) bands. This splitting approaches zero along the (0,0)-->(pi,pi) nodal line and is not observed in single layer Bi(2)Sr(2)CuO(6+delta) (Bi2201), indicating that the splitting is due to the long sought after bilayer splitting effect. The splitting has a magnitude of approximately 75 meV near the middle of the zone, extrapolating to about 110 meV near the (pi,0) point. The existence of these two bands also helps to clear up the recent controversy concerning the topology of the Fermi surface.

Doubling of the bands in overdoped Bi2Sr2CaCu2O8+*: Evidence for c-axis bilayer coupling - art no. 117002

We present high resolution angle resolved photoemission data of the bilayer superconductor Bi(2)Sr(2)CaCu(2)O(8+delta) (Bi2212) showing a clear doubling of the near E(F) bands. This splitting approaches zero along the (0,0)-->(pi,pi) nodal line and is not observed in single layer Bi(2)Sr(2)CuO(6+delta) (Bi2201), indicating that the splitting is due to the long sought after bilayer splitting effect. The splitting has a magnitude of approximately 75 meV near the middle of the zone, extrapolating to about 110 meV near the (pi,0) point. The existence of these two bands also helps to clear up the recent controversy concerning the topology of the Fermi surface.