https://doi.org/10.1007/s100510051125
Extended dx2 - y2-wave superconductivity. Flat nodes in the gap and the low-temperature asymptotic properties of high-Tc superconductors
1
Dipartimento di Fisica e Astronomia dell'Università di Catania and Istituto Nazionale di
Fisica della Materia, U.d.R.
di Catania, 57, Corso Italia, 95129 Catania, Italy
2
Institutt for Fysikk, Norges Teknisk-Naturvitenskapelige Universitet NTNU, Sem Sæ
landsvei 9, Gløshaugen, 7491
Trondheim, Norway
Received:
19
November
1999
Published online: 15 May 2000
Remarkable anisotropic structures have been recently observed
in the order parameter of the underdoped superconductor
Bi2Sr2CaCu2O
.
Such findings are strongly suggestive of deviations from a
simple
-wave picture of high-Tc
superconductivity, i.e.
.
In particular, flatter nodes in
are observed along the
directions in
-space, than within this simple
model for a d-wave gap.
We argue that nonlinear corrections in the
-dependence of
near the nodes introduce new energy scales, which
would lead to deviations in the predicted power-law asymptotic
behaviour of several measurable quantities, at low or intermediate
temperatures.
We evaluate such deviations, either analytically or numerically,
within the interlayer pair-tunneling model, and within yet another
phenomenological model for a d-wave order parameter.
We find that such deviations are expected to be of different sign in
the two cases.
Moreover, the doping dependence of the flatness of the gap near the
nodes is also attributable to Fermi surface effects, in addition to
possible screening effects modifying the in-plane pairing kernel,
as recently proposed.
PACS: 74.25.-q – General properties; correlations between physical properties in normal and superconducting states / 74.25.Jb – Electronic structure / 74.20.Mn – Nonconventional mechanisms / 74.72.Hs – Bi-based cuprates
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2000