Condensed Matter Physics Seminar

Monday, February 22, 1999, 1:30 p.m.
Physics Building, Room 0405

Quantum criticality and pseudogap in cuprates

Joerg Schmalian

(University of Illinois, Urbana and Oxford University, UK)

Abstract:  Two closely  related  aspects of underdoped cuprate superconductors will be discussed:  the magnetic scaling behavior of the low energy spin dynamics and the pseudogap phenomenon. These aspects are investigated  within a magnetic  scenario of cuprates. The anomalous behavior of the low energy spin excitations is  argued to be caused by the proximity to a zero  temperature quantum critical point. In  contrast to the situation in insulating antiferromagnets, this quantum critical point takes into account  the modified spin dynamics due to doped charge carriers. The theoretical results  explain the unusual scaling behavior as observed  in NMR and neutron scattering experiments. Furthermore, a theory for the single particle pseudogap in terms of pairing precursors will be  presented. It will be shown that the non-Fermi-liquid character of the charge carriers, caused by the interaction with spin excitations, offers an explanation for the occurrence and temperature dependence of the single particle pseudogap. It is shown that the pseudogap crossover temperature and the scaling behavior due to quantum criticality are  closely related phenomena.

Host: Sankar Das Sarma

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