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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