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TT: Tiefe Temperaturen

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

TT 30.8: Vortrag

Donnerstag, 30. März 2006, 15:45–16:00, HSZ 02

Nuclear Magnetic Resonance Studies of Rare Earth co-doped Lanthanum Cuprates — •Hans-Joachim Grafe^1,2, Nicholas J. Curro², Markus Hücker³, and Bernd Büchner¹ — ¹IFW Dresden, Germany — ²Los Alamos National Laboratory, NM , USA — ³Physics Department, Brookhaven National Laboratory, Upton NY, USA

¹⁷O and ⁶³Cu Nuclear Magnetic Resonance (NMR) results in stripe ordered La_1.8−xEu_0.2Sr_xCuO₄ will be presented. At low temperatures the local electric field gradient (EFG) as well as the absolute intensity of the NMR signal of the planar O site exhibit a dramatic decrease. We interpret these results as microscopic evidence for a spatially inhomogeneous charge distribution, where the NMR signal from O sites in the domain walls of the spin density modulation are wiped out due to large hyperfine fields, and the remaining signal arises from the intervening Mott insulating regions. At similar temperatures the Cu NMR signal experiences a complete wipe out, suggesting that the oxygens are wiped out by the same mechanism that renders the Cu invisible, namely slowly fluctuating Cu electronic spins. Despite of this static magnetic and charge order, the Knight shift exhibits the same pseudogap-like temperature dependence as in superconducting La_2−xSr_xCuO₄.