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TT: Tiefe Temperaturen

TT 30: Superconductivity: Twenty Years High-T_c Cuprates - Recent Progress

TT 30.16: Vortrag

Donnerstag, 30. März 2006, 18:00–18:15, HSZ 02

From d- to p-wave pairing in the t-t’ Hubbard model at zero temperature — •K. Held and R. Arita — Max-Planck Institut für Festkörperphysik, Stuttgart

The Hubbard model is commonly considered to be relevant for unconventional superconductors like cuprates and ruthenates. For a more thorough insight into the physics of this model (is it explaining superconductivity?), the dynamical cluster approximation (DCA) combined with quantum Monte Carlo (QMC) [1] is a promising approach. DCA(QMC) is however restricted to rather high temperatures T. A prediction of superconducting phases at low-T is hence problematic. As a new path to low T, a projective QMC algorithm for impurity problems was recently developed [2], allowing for the solution of the dynamical mean field approximation (DMFT) equations in the T→0 limit.

We extend this projective QMC algorithm to DCA [3], and apply it for studying pair susceptibilities of the two-dimensional Hubbard-model with next-nearest neighbor hopping. In particular, we identify which pairing symmetry is dominant in the U-n parameter space (U: repulsive Coulomb interaction; n: electron density). We find that p_x+y- (d_x²−y²-) wave is dominant among triplet (singlet) pairings -at least for 0.3<n<0.8 and U<=4t. The crossover between d_x²−y²-wave and p_x+y-wave occurs around n∼ 0.4.

[1] M.H. Hettler et al., Phys. Rev. B 58 R7475 (1998).

[2] M. Feldbacher, K. Held, and F. F. Assaad, Phys. Rev. Lett. 93, 136405 (2004).

[3] K. Held and R. Arita, cond-mat/0508639.