Consensed Matter Seminar Announcement Prof. Oleg Sushkov University of New South Wales " Theory of Incommensurate Magnetic Correlations Across the Insulator-Superconductor Transition in Underdoped La2-XSRxCuO" Date: Thursday, January 13, 2005 Time: 4:10 pm 416 Physics Abstract: The main feature in the elastic neutron scattering of La$_{2-x}$Sr$_x$CuO$_4$ is the existence of incommensurate peaks with positions that jump from 45$^\circ$ to 0$^\circ$ at 5\% doping. We show that the spiral state of the $t-t'-t''-J$ model with realistic parameters describes this data perfectly. We explain why in the insulator the peak is at 45$^\circ$ while it switches to 0$^\circ$ precisely at the insulator-metal transition. The calculated positions of the peaks are in agreement with the data in both phases. The dc hopping conductivity in the insulating phase is anisotropic because of the spin spiral. The calculated anisotropy also agrees with experimental data.

E-Mail: sushkov@phys.unsw.edu.au
Web Page: unsw.edu.au