We present an angle-resolved photoemission doping dependence study of the n-type cuprate superconductor Nd(2-x)Ce(x)CuO(4+/-delta), from the half-filled Mott insulator to the T(c) = 24 K superconductor. In Nd2CuO4, we reveal the charge-transfer band for the first time. As electrons are doped into the system, this feature's intensity decreases with the concomitant formation of near- E(F) spectral weight. At low doping, the Fermi surface is an electron-pocket (with volume approximately x) centered at (pi,0). Further doping leads to the creation of a new holelike Fermi surface (volume approximately 1+x) centered at (pi,pi). These findings shed light on the Mott gap, its doping evolution, as well as the anomalous transport properties of the n-type cuprates.

Angle-resolved photoemission studies on Sr 2 CuO 2 Cl 2 at a temperature below its Néel temperature reveal detailed momentum dependent line shape changes as a function of wave vector. While a sharp quasiparticlelike peak is observed near (p͞2, p͞2), broad peaks are observed near (p, 0). Additional second and third neighbor hopping terms must be added to the t-J Hamiltonian to account for both the dispersion and the line shape. It is found that this Hamiltonian can be used to explain the measured momentum dependent spectral function for hole-doped materials, both underdoped and overdoped, as well as electron-doped materials. [S0031-9007(98)06100-6]

The electronic structure of heavily overdoped Bi2Sr2CaCu2O 8+δ is investigated by angle-resolved photoemission spectroscopy. The long-sought bilayer band splitting in this two-plane system is observed in both normal and superconducting states, which qualitatively agrees with the bilayer Hubbard model calculations. The maximum bilayer energy splitting is about 88 meV for the normal state feature, while it is only about 20 meV for the superconducting peak. This anomalous behavior cannot be reconciled with the quasiparticle picture.PACS numbers: 71.18.+y, 74.72.Hs, 79.60.Bm High temperature superconductors (HTSC's), as doped Mott insulators, show strong doping dependent behavior. The underdoped regime of the HTSC's is characterized by its unconventional properties, such as the pseudogap and non-Fermi liquid transport behavior. On the other hand, the overdoped regime is considered to be more "normal", partly because of the absence of a pseudogap and more Fermi liquid-like behavior. It is very challenging and important for HTSC theories to be able to explain the phenomenology in both regimes. Angle resolved photoemission spectroscopy (ARPES), one of the most direct probes of the electronic structure, has contributed greatly to the understanding of the electronic structure of the HTSC's. However, most systems studied by ARPES have either low T c 's (below 40K for La 2−x Sr x CuO 4+δ (LSCO), and Bi 2 Sr 2 CuO 6+δ (Bi2201)), or doping limitations (only up to slightly overdoping for Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212) and YBa 2 Cu 3 O 7−y (YBCO)). For a complete understanding, it is very important to study the heavily overdoped systems, especially Bi2212, which is the most studied system by ARPES.Recent advances in high pressure annealing techniques have made it possible to synthesize heavily overdoped Bi2212. In this paper, we report ARPES measurements of the electronic structure of heavily overdoped Bi2212. We show that the long-sought bilayer band splitting (BBS) exists for both normal and superconducting states of this material over large fraction of the Brillouin zone. The detection of the BBS, which has been predicted by band structure calculations [1,2], but not observed in earlier ARPES data [3], enables us to address several important issues. First, it provides a very detailed test for the theoretical calculations, with our experimental results favoring the bilayer Hubbard model [4] over LDA calculations [1,2]. Second, it shows the novel result that the bilayer splitting energy in the superconducting state is only about 23% of the normal state splitting. Third, it provides an explanation for the detection of a "peak-diphump" structure in the normal state of heavily overdoped samples [5,6].Heavily overdoped Bi2212 samples (T C (onset) = 65 K, ∆T C (10% ∼ 90%) = 3 K, denoted as OD65) were synthesized by annealing floating-zone-grown single crystals under oxygen pressure P O2 = 300 atm at 300• C for two weeks, and characterized by various techniques. Magnetic susceptibility measurements show that the presence of a s...