Regensburg 2010 – wissenschaftliches Programm
TT 24.14: Vortrag
Mittwoch, 24. März 2010, 18:00–18:15, H19
Origin of the nondispersive wavevector component at q→=(3/4,0) in the electronic structure of cuprate supercondutors — •Jürgen Röhler — Universität zu Köln, 50937 Köln
A direct spectroscopic fingerprint of phase-incoherent precursor superconductivity in cuprates was recently obtained by spectroscopic imaging spectroscopy uncovering up to T=1.5 Tc dispersive Bogoliubov quasiparticle excitations (± E< 35 meV) which coexist with true nondispersive and locally symmetry breaking excitations at the pseudogap energy scale (± E≃ 120 meV) . While the low-energy excitations are homogenously distributed in r-space, the high-energy excitations appear as static domains (width 4a) scattered in random orientation on the xy-plane, but along no preferred Cu-O direction. This "glassy" component of the electronic structure is in conflict with "stripes" flowing preferrentially in one Cu-O direction. The 4a wide O-Cu-O-Cu-O-Cu-O-Cu-O domains exhibit an internal 3a structure by dominant charge contrast maxima at the central O site and the two outmost Cu sites. We analyze the corresponding wavevector components at q→=(3/4,0);(0,3/4) as a signature of bond centered quartets of Zhang-Rice hole singlets forming pseudomoleculss with a characteristic length of 3a . The internally antiferromagnetic 3a pseudomolecules may act as bosonic pairing centers exchanging resonantly paired quasiparticles with the dispersive low-energy sector of the superconducting condensate.
 J. Lee et al., Science 325 (2009), 1099.
 J. Röhler, Physica C460-62 (2007), 374.