Magnetic and Raman response properties in La2CuO4 Complex Behavior in Correlated Electron Systems Lorentz Center – 08/01 until 08/19 - 2005 Magnetic and Raman response properties in La2CuO4   Marcello Barbosa da Silva Neto Lara Benfatto Vladimir Juricic Cristiane de Morais Smith

Magnetism in the cuprates

NLSM

Unusual magnetic susceptibility anisotropies ASHCROFT & MERMIN A. Lavrov et al. PRL (‘01) Unexpected hierarchy of T=0 susceptibilities!

The field induced mode – FIM Appearance of a second magnetic mode for B || b, and ONLY for that orientation, in (RR) configuration Only ONE magnetic mode for the (ab) and (RL) polarization configurations of the light A. Gozar et al., PRL (‘04)

Magnetic anisotropies Tilting + SO coupling

Generalized nonlinear Sigma Model M.B.Silva Neto, L.Benfatto, V.Juricic and C.Morais-Smith, cond-mat/0502588

Magnetic Susceptibility Traditional UNIFORM susceptibility NEW STAGGERED contribution!!!!

Comparison with experiment

The electric-dipole Hamiltonian Elastic scattering

Electric dipole selection rules One-magnon energy!

The final electric-dipole Hamiltonian a b c a b c or (ab) channel or (cb) channel M.B.Silva Neto and L.Benfatto, cond-mat/0507103

Electric field ALWAYS parallel to the ab plane!!! Raman spectroscopy Backscattering Geometry Electric field ALWAYS parallel to the ab plane!!!

One-magnon Raman Intensity A. Gozar et al., PRL (‘04)

Rotation of spin quantization basis – B||b

The field induced mode - FIM

Hole doping and spirals Hole doping – dipolar frustration of the AF background Anisotropies give robustness to the Neel ground state – DM gap vanishes at 2% - V. Juricic et al. in preparation! Above 2% instability to a spiral phase New periodicity! N.Hasselman et al., PRB (‘04)

Topological defects and transport Doped holes – cores of topological defects Dynamics of defects is dissipative – bath of magnons V.Juricic et al., PRL (‘04)

Conclusions Dzyaloshinskii Moryia interaction accounts for the unusual hierarchy of T=0 susceptibilities and for the anisotropic magnetic response. It is also responsible for the rotation of the spin quantization basis and appearance of the FIM. It gives robustness to the Neel ground state and vanishes at 2% where the ground state becomes a spiral.