  Polarization selectivity of light-field-induced charge localization was
investigated in an organic metal alpha-(BEDT-TTF)2I3 with a triangular lattice.
Dependences of transient reflectivity spectra on polarizations of the 7-fs pump
and probe lights indicate that a short-range charge order (CO) is efficiently
induced from the metallic phase for the pump polarization perpendicular to the
1010-type CO axis. Numerical solution of a time-dependent Schrodinger equation
clarified that the 1010-CO is induced by field-induced re-distribution of
charges cooperating with competing inter-site Coulomb repulsions in the
triangular lattice.
