Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 15: Superconductivity - Properties, Electronic Structure, Order Parameter I

TT 15.8: Vortrag

Samstag, 5. März 2005, 16:00–16:15, TU H2053

Two length scales in the crystalline electronic state of underdoped cuprate superconductors — •Jürgen Röhler — Universität zu Köln, D-50937 Köln, Germany

Spatial- and energy-resolved differential tunneling measurements from STM have shown evidence for a crystalline electronic structure in the pseudogap regime of lightly doped cuprate superconductors [1]. The conductance exhibits minima at the perimeter atoms of a four Cu₂O-unit-cell square “checkerboard”. The internal electronic structure of the 4a× 4a squares consists of 3× 3 conductance maxima, incommensurate with the atomic lattice. We suggest to relate this electronic crystal structure with a “supersolid” of paired self-protecting singlets (PSPS) [2]. Hole pairs underlying not only a non-double-occupancy constraint for the copper sites, but also for the oxygen cages, extend over 4a (4 oxygen cages), and may cause a 4a× 4a modulation of the electronic structure. Maxima in the local density of states, however, are expected to occur with a periodicty of 3a (4 copper sites). The interference between the 4a and 3a length scales yields a possible explanation for the atomic-scale electronic structure variations observed within the checkerboard.

[1] T. Hanaguri et al., Nature 430, 1001 (2004), cond-mat/0409102.

[2] J. Röhler, J. Supercond. 17, 159 (2004), cond-mat/0307310.