A Time-Resolved Second Harmonic Generation Study of a Cuprate Mott Antiferromagnet

Here we report a study of the cuprate antiferromagnetic Mott insulator Ba2Cu3O4Cl2 using rotational anisotropy second harmonic generation (RA-SHG), which is sensitive to the underlying lattice and magnetic symmetries of a crystal. Our data reveal a four-fold symmetric RA-SHG pattern above the Neel temperature dominated by electric quadrupole radiation. Below the Neel temperature, a magnetic-dipole SHG process emerges that breaks the four-fold symmetry of the underlying lattice, consistent with earlier reports of a canted antiferromagnetic state. Pump-probe time-resolved SHG experiments reveal that photo-generated carriers, populated by optically exciting the crystal with a photon energy above the Mott gap, rapidly quench the antiferromagnetic order. The far-from-equilibrium dynamics as a function of temperature and pump fluence will be discussed.