Magnetic and Raman response properties in La2CuO4

1
Magnetic and Raman response properties in La2CuO4
Complex Behavior in Correlated Electron
Systems Lorentz Center 08/01 until 08/19 - 2005
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 T0 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/0502588
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
L1
L0
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/0507103
13
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 Bb
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 T0 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.