Effects of interlayer interaction on the superconducting state inYBa2Cu3

Abstract

For a two-layer system in a weak-coupling BCS formalism any interlayer interaction, regardless of its sign, enhances the critical temperature. The sign has an effect upon the relative phase of the order parameter in each of the two planes but not upon its magnitude. When one of the planes has a dispersion consistent with CuO chains and no intrinsic pairing interaction there is both an enhancement of the critical temperature and an sϩd mixing in both layers as the interlayer interaction is increased. The magnetic penetration depth, c-axis Josephson tunneling, density of states, and Knight shift are calculated for several sets of model parameters.

Tunneling Spectroscopy ofc-AxisY1−xCaxBa2Cu3Ngai1, Atkinson2, Wei3 2007Phys. Rev. Lett.188180View full textAdd to dashboardCite

“…Such coupling would imply that the superconductivity in YBCO is essentially multiband in nature [6,7,8,9,10,11], and could conceivably affect its pairing symmetry. In fact, recent pair-tunneling experiments [12,13] have revealed a twofold, d x 2 −y 2 + s pairing symmetry [14,15] in optimallydoped YBCO, with the d-wave node lines rotated away from the chain axis.At present it is not yet clear from these pair-tunneling experiments whether the observed d + s pairing symmetry is intrinsic to the planes [16], or it is an effect of coupling between the plane and chain bands [6,7,8,9,10]. Quasiparticle tunneling spectroscopy could help to elucidate this issue, by revealing multigap features in the excitation spectrum and by providing information about the pairing symmetry.…”

“…Since long-range order cannot be easily sustained in one-dimension, the apparent presence of superfluid density in the chains suggests that the plane and chain bands are electronically coupled. Such coupling would imply that the superconductivity in YBCO is essentially multiband in nature [6,7,8,9,10,11], and could conceivably affect its pairing symmetry. In fact, recent pair-tunneling experiments [12,13] have revealed a twofold, d x 2 −y 2 + s pairing symmetry [14,15] in optimallydoped YBCO, with the d-wave node lines rotated away from the chain axis.…”

“…At present it is not yet clear from these pair-tunneling experiments whether the observed d + s pairing symmetry is intrinsic to the planes [16], or it is an effect of coupling between the plane and chain bands [6,7,8,9,10]. Quasiparticle tunneling spectroscopy could help to elucidate this issue, by revealing multigap features in the excitation spectrum and by providing information about the pairing symmetry.…”

Disorder and chain superconductivity inYBa2Cu3O7Atkinson1 1999Phys. Rev. B394450View full textAdd to dashboardCite

“…The simplest model consistent with d-wave chain superconductivity is the proximity model, in which the pairing interaction resides in the CuO 2 planes and chain superconductivity occurs through the hybridization of plane and chain wavefunctions. The failure of this model (discussed below) to describe penetration depth experiments, 18 has led several authors [19][20][21]11 to abandon the premise of a pairing interaction contained exclusively within the CuO 2 planes.In this work, we show that a small amount of chain disorder is sufficient to reconcile the proximity model with experiments. We model a CuO 2 -CuO-CuO 2 trilayer with a three-band tight-binding Hamiltonian in which the isolated chain and plane layers have one and twodimensional dispersions respectively, coupled through single electron hopping.…”

“…The simplest model consistent with d-wave chain superconductivity is the proximity model, in which the pairing interaction resides in the CuO 2 planes and chain superconductivity occurs through the hybridization of plane and chain wavefunctions. The failure of this model (discussed below) to describe penetration depth experiments, 18 has led several authors [19][20][21]11 to abandon the premise of a pairing interaction contained exclusively within the CuO 2 planes.…”