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TT: Tiefe Temperaturen

TT 3: Supraleitung: Elektronenstruktur, Phononen, Tunneln, Ordnungsparameter I

TT 3.11: Talk

Monday, March 24, 2003, 12:00–12:15, HSZ301

Screening of impurity moments in d-wave superconductors — •Marijana Kircan and Matthias Vojta — Institut für Theorie der Kondensierten Materie, Universität Karlsruhe

We discuss the dynamics of impurity moments, either induced by non-magnetic impurities like Zn or arising from doping magnetic impurities, in cuprate d-wave superconductors. The moments are coupled to the fermionic quasiparticles of the host superconductor as well as to collective spin fluctuations. The effective Fermi-Bose Kondo model shows a quantum phase transition between a free-moment and a strong-coupling phase, which can be driven, e.g., by varying the strength of host spin fluctuations. We argue that this transition has been observed in recent NMR experiments, where Kondo screening appears to be suppressed in the underdoped regime. The Kondo scattering leads to a characteristic peak at small, but finite energy in the local density of states which is related to recent STM measurements on Zn-doped BSCCO.