Spectroscopic study of stripe pattern formation induced by current injection in a charge-transfer complex

A stripe pattern with a spacing of a few micrometers is observed to show up on the crystal surface of a potassium 7,7',8,8'-tetracyanoquinodimethane (K-TCNQ) upon the current-induced local insulator-metal transition. The spatially resolved reflectivity and Raman spectroscopies have shown that the stripe is a consequence of periodic phase separation with alternate dimerized and less-dimerized domains in the TCNQ stacks. The periodic modulation of the electronic state is generated in order to minimize the energy of the lattice strain, arising from the current-induced relaxation of the Peierls distortion.