Condensed Matter Physics Seminar
Friday, January 29, 1999, 2 p.m.
Plant Sciences Building, Room 1130
Unified theory of superconductivity and antiferromagnetism in the high-Tc
cuprates
Eugene Demler
(Institute for Theoretical Physics, University of California at Santa Barbara)
Abstract: Understanding the microscopic mechanism of high
$T_c$ superconductivity requires quantitatively accounting for the superconducting
condensation energy. Within the $t$-$J$ model of copper-oxides, the
condensation energy can be related to the change in the dynamical spin
structure factor between the superconducting and the normal states.
By analyzing previous experimental data, we show that the change associated
with the resonant neutron scattering peak found in $YBa_2Cu_3O_7$ can quantitatively
account for the condensation energy. We argue that this analysis suggests
a microscopic mechanism for high $T_c$ superconductivity, where antiferromagnetic
exchange energy is saved in the superconducting state through the coupling
to a triplet particle-particle resonance. A review of this collective mode
in the t-J and Hubbard models is given and its role in unifying d-wave
superconductivity and antiferromagnetism into SO(5) symmetry will be shown.
Effective low energy SO(5) theory of the high Tc cuprates is considered
and effect of the fermions is discussed. Possible experimental tests are
reviewed.
Host: Sankar Das Sarma
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