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We used high resolution angle-resolved photoemission spectroscopy to reveal the Fermi surface and key transport parameters of the metallic state of the layered Colossal Magnetoresistive (CMR) oxide La 1.2 Sr 1.8 Mn 2 O 7 . With these parameters the calculated inplane conductivity is nearly one order of magnitude larger than the measured DC conductivity. This discrepancy can be accounted for by including the pseudogap which removes at least 90% of the spectral weight at the Fermi energy. Key to the pseudogap and many other properties are the parallel straight Fermi surface sections which are highly susceptible to nesting instabilities. These nesting instabilities produce nanoscale fluctuating charge/orbital modulations which cooperate with Jahn-Teller distortions and compete with the electron itinerancy favored by double exchange.3

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.

We have carried out extensive high-resolution angle-resolved photoemission ͑ARPES͒ experiments on Bi 2 Sr 2 CaCu 2 O 8ϩ␦ 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 CuO 2 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 (,0), in good agreement with the predictions of corresponding first-principles simulations. Our detailed analysis indicates that the size of the bilayer splitting is only weakly dependent on the doping level, implying that electronic excitations continue to maintain some degree of coherence even in the underdoped regime.

We present a reexamination of the electronic structure and Fermi surface (FS) topology of Bi-Sr-Ca-Cu-O (BSCCO) as obtained from angle-resolved photoemission experiments. 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. In particular, we have found a FS that is centered around the G point and contains electronlike portions, and we observe a depletion of spectral weight aroundM. The flat bands observed at other photon energies may indicate the presence of two electronic components in the cuprates.