Vendredi 27 novembre 2015 à 14h15
Auditoire Stueckelberg, Ecole de Physique

Strong Superconducting Fluctuations leading to a Giant Phonon Anomaly in the Pseudogap Phase of Underdoped Cuprates.

Thomas Maurice Rice, ETH Zürich

As the hole density decreases and the Mott insulator is approached, umklapp scattering processes increase in importance. The well studied D-Mott Insulator state in Hubbard 2-leg ladders shows that these can introduce a gap in the 2-particle spectrum and transform a superconducting gap into an insulating pseudogap, starting at antinodal. Long range ordered superconductivity is then confined to 4 anisotropic pockets centered on the nodal directions. A consistent description of the break up the Fermi surface observed in ARPES experiments follows, as proposed earlier by Yang, Rice & Zhang. The Fermi surface surface breakup in turn leads to a breakup of the superconducting d-wave order parameter into two subband amplitudes along (1,1) & (1,-1) directions and to a low energy Leggett mode due to phase fluctuations between them. This leads to a large increase in the temperature range of superconducting fluctuations with an overdamped Leggett mode. Almost resonant scattering of intersubband phonons to a state with a pair of Leggett modes, causes anomalously strong phonon damping at wavevectors connecting the ends of the pockets, in this temperature range. A close connection in both temperature and hole density between these anomalously strong superconducting fluctuations and the Giant Phonon Anomaly reported by Le Tacon et al. {Nature Physics 2014} follows. Y.H. Liu, R. Konik, T.M. Rice & F.C. Zhang arXiv1506.01258