D. J. Scalapino

The case for dx2 − y2 pairing in the cuprate superconductors

Abstract The nature of the orbital structure of the pairs in the superconducting phase of the high-temperature superconducting cuprates remains one of the central questions in this field. Here we examine the possibility that the superconducting state of these materials is characterized by d x 2 − y 2 pairing. We begin by looking theoretically at why this type of pairing might be favored in a strongly correlated system with a short-range Coulomb interaction. Then we turn to the experimental question of how one would know if d x 2 − y 2 pairing were present.

Near-degeneracy of several pairing channels in multiorbital models for the Fe pnictides

Weak-coupling approaches to the pairing problem in the iron pnictide superconductors have predicted a wide variety of superconducting ground states. We argue here that this is due both to the inadequacy of certain approximations to the effective low-energy band structure, and to the natural near degeneracy of different pairing channels in superconductors with many distinct Fermi surface sheets. In particular, we review attempts to construct two-orbital effective band models, the argument for their fundamental inconsistency with the symmetry of these materials, and compare the dynamical susceptibilities of two- and five-orbital tight-binding models. We then present results for the magnetic properties, pairing interactions and pairing instabilities within a five-orbital tight-binding random phase approximation model. We discuss the robustness of these results for different dopings, interaction strengths and variations in band structures. Within the parameter space explored, an anisotropic, sign-changing s-wave (A1g) state and a (B1g) state are nearly degenerate, due to the near nesting of Fermi surface sheets.

Distinct Fermi-momentum dependent energy gaps in deeply underdoped Bi2212.

We used angle-resolved photoemission spectroscopy applied to deeply underdoped cuprate superconductors Bi2Sr2Ca(1–x)YxCu2O8 (Bi2212) to reveal the presence of two distinct energy gaps exhibiting different doping dependence. One gap, associated with the antinodal region where no coherent peak is observed, increased with underdoping, a behavior known for more than a decade and considered as the general gap behavior in the underdoped regime. The other gap, associated with the near-nodal regime where a coherent peak in the spectrum can be observed, did not increase with less doping, a behavior not previously observed in the single particle spectra. We propose a two-gap scenario in momentum space that is consistent with other experiments and may contain important information on the mechanism of high–transition temperature superconductivity.

Minimal two-band model of the superconducting iron oxypnictides

Following the discovery of the Fe-pnictide superconductors, local-density approximation (LDA) band structure calculations showed that the dominant contributions to the spectral weight near the Fermi energy came from the

Resonating Valence Bond Theory of Coupled Heisenberg Chains

\text{Fe}\text{ }3d

Theory of intermodulation in a superconducting microstrip resonator

orbitals. The Fermi surface is characterized by two hole surfaces around the

Simple models for heterogeneous catalysis: Phase transition‐like behavior in nonequilibrium systems

\ensuremath{\Gamma}

Conserving approximations for strongly fluctuating electron systems. I. Formalism and calculational approach

point and two electron surfaces around the

Strength of the spin-fluctuation-mediated pairing interaction in a high-temperature superconductor

M

Fluctuation phenomena in tunnel junctions

point of the two Fe/cell Brillouin zone. Here, we describe a two-band model that reproduces the topology of the LDA Fermi surface and exhibits both ferromagnetic and