Linear dichroism of CdSe nanodots: Large anisotropy of the band-gap absorption induced by ground-state dipole moments

We measured the electric field induced linear dichroism for a wide range of sizes of CdSe nanocrystals. Large ground-state dipole moments were observed, especially for the smallest crystals. In these, we found a very large anisotropy of the absorption and most of the dipole strength is along the direction of the ground-state dipole moment. For the anisotropy, we propose a mechanism for intensity borrowing from intraband transitions, induced by the field of the ground-state dipole moment. © 2008 The American Physical Society.