Pinned Balseiro-Falicov model of tunneling and photoemission in the cuprates

Abstract

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.

Dispersion of ordered stripe phases in the cuprates

“…Ref. 72 ( Fig. 19) showed that the changes in BSCCO at T c can be interpreted in terms of enhanced fluctuations in the normal state; a similar calculation was presented by Chubukov and Morr 73 .…”

“…Superconductivity will also renormalize the gap on the charged stripes (as discussed for a related model in Ref. 72), but this will be a secondary effect.…”

Phase separation models for cuprate stripe arrays

“…The first is a Class A paramagnetic stripe, stabilized by electron-phonon coupling 63,64 , while the second has dominant electronelectron coupling, with (Class B) magnetic charged stripe order.…”

Dynamical charge susceptibility in layered cuprates: Beyond the conventional random-phase-approximation scheme

“…There are few informative reviews and papers devoted to this problem( see for example [1][2][3][4]). One of the most reasonable point of view is that a pseudogap in the density of states shows up due to an instability in two-dimensional copper-oxygen planes.…”