d -wave superconductivity in coupled ladders
J. P. L. Faye, S. R. Hassan, P.V. Sriluckshmy, G. Baskaran, D. Sénéchal
Abstract
We study the one-band Hubbard model on the trellis lattice, a two-dimensional frustrated lattice of coupled two-leg ladders, with hopping amplitude
t
within ladders and
t
′
between ladders. For large
U/t
this is a model for the cuprate Sr
14−x
Ca
x
Cu
24
O
41
. We investigate the phase diagram as a function of doping for
U=10t
using two quantum cluster methods: The variational cluster approximation (VCA), with clusters of sizes 8 and 12, and Cellular dynamical mean field theory (CDMFT), both at zero temperature. Both methods predict a superconducting dome, ending at roughly 20\% doping in VCA and 15\% in CDMFT. In VCA, the superconducting order parameter is complex in a range of doping centered around 10\%, corresponding to bulk chiral,
T
-violating superconductivity. However, the CDMFT solution is not chiral. We find evidence for a migration of the Cooper pairs from the inter-ladder region towards the plaquettes as doping is increased.