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

2. Magnetism in the cuprates

3. NLSM

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

5. 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)

6. Magnetic anisotropies
Tilting +
SO coupling

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

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

9. Comparison with experiment

10. The electric-dipole Hamiltonian
Elastic scattering

11. Electric dipole selection rules
One-magnon energy!

12. 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/

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

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

15. Rotation of spin quantization basis – B||b

16. The field induced mode - FIM

17. 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)

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

19. 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.