We investigate the doping dependence of the penetration depth versus temperature in electron-doped Pr(2-x)Ce(x)CuO(4-delta) using a model which assumes the uniform coexistence of (mean-field) antiferromagnetism and superconductivity. Despite the presence of a d(x2-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.

We present a three-band Hubbard Hamiltonian and the associated Cu Kappa-edge resonant inelastic x-ray scattering (RIXS) spectra for electron- and hole-doped cuprates over a wide range of energy and momentum transfers. By comparing computed spectra for the unfilled case with the corresponding results for 15% electron or hole doping at two different values of the effective Hubbard parameter , generic signatures of the collapse of the magnetic gap and the characteristic momentum dependencies and evolution of the spectra with doping are identified. Available RIXS data support the gap collapse scenario for electron-doped cuprates, but the situation in hole-doped systems is found to be less clear.

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.

The smooth evolution of the tunneling gap of Bi2Sr2CaCu2O8 with doping from a pseudogap state in the underdoped cuprates to a superconducting state at optimal and overdoping, has been interpreted as evidence that the pseudogap must be due to precursor pairing. We suggest an alternative explanation, that the smoothness reflects a hidden SO(N) symmetry near the (π, 0) points of the Brillouin zone (with N = 3, 4, 5, or 6). Because of this symmetry, the pseudogap could actually be due to any of a number of nesting instabilities, including charge or spin density waves or more exotic phases.We present a detailed analysis of this competition for one particular model: the pinned Balseiro-Falicov model of competing charge density wave and (s-wave) superconductivity. We show that most of the anomalous features of both tunneling and photoemission follow naturally from the model, including the smooth crossover, the general shape of the pseudogap phase diagram, the shrinking Fermi surface of the pseudogap phase, and the asymmetry of the tunneling gap away from optimal doping. Below Tc, the sharp peak at ∆1 and the dip seen in the tunneling and photoemission near 2∆1 cannot be described in detail by this model, but we suggest a simple generalization to account for inhomogeneity, which does provide an adequate description.We show that it should be possible, with a combination of photoemission and tunneling, to demonstrate the extent of pinning of the Fermi level to the Van Hove singularity. A preliminary analysis of the data suggests pinning in the underdoped, but not in the overdoped regime.

The Fermi surface (FS) of Bi2Sr2CaCu2O 8+δ (Bi2212) predicted by band theory displays Birelated 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 Bias well as Tl-and Hg-based compounds indicate that lifting of the cation-derived band with hole doping is a general property of the electronic structures of the cuprates.PACS numbers: 74.72. Hs,74.25.Jb,71.18.+y, First-principles band theory computations on the cuprates have become a widely accepted tool for gaining insight into their electronic structures, spectral properties, Fermi surfaces (FS's), and as a starting point for constructing theoretical models for incorporating strong correlation effects beyond the framework of the local-density approximation (LDA) underlying such calculations 1,2,3,4 . For example, in the double layer Bicompound Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212) − perhaps the most widely investigated cuprate − the LDA generated band structure 5,6 is commonly invoked to describe the doped metallic state of the system. Band theory however clearly predicts the FS of Bi2212 to contain a FS pocket around the antinodal point M (π, 0) as a Bi-O band drops below the Fermi energy (E F ), but such FS pockets have never been observed experimentally 7 . This 'Bi-O pocket problem' is quite pervasive and occurs in other Bi-compounds. 8 Similarly, Tl-and Hg-compounds display cation-derived FS pockets, presenting a fundamental challenge for addressing on a first-principles basis issues related to the doping dependencies of the electronic structures of the cuprates.In this Letter, we show how the cation-derived band responsible for the aforemenentioned FS pockets is lifted above E F when hole doping effects are properly included in the computations. Detailed results for the case of Bi2212 are presented, where hole doping is generated either by substituting Pb for Bi or by adding excess oxygen in the Bi-O planes. With 20% Pb doping in the orthorhombic crystal structure, the Bi-O band lies ≈ 1 eV above E F and the remaining bonding and antibonding FS sheets are in remarkable accord with the angleresolved photoemission (ARPES) measurements on an overdoped Bi2212 single crystal 9 . Below a critical hole doping level, the Bi-O band falls below E F and, as a result of this self-doping effect, further reduction in the hole doping level no longer reduces the number of holes in the CuO 2 layers. We argue that the underlying mechanism at play here is that hole doping reduces the effective positive charge in the Bi-O donor layers, which then reduces the tendency of the electrons to 'flow back' and self-dope the material. We have also carried out computatio...