Electric-field-dependent energy structure of quasi-one-dimensional conductor $p$-TaS$_3$

Energy structure of the Peierls gap in orthorhombic TaS₃ is examined by spectral study of photoconduction. The gap edge and energy levels inside the Peierls gap are observed. The amplitude of the energy levels is found to depend on both the temperature and the electric field. The electric field of the order of 1–10 V/cm affects the energy levels and leads to the redistribution of intensity between peaks. The small value of the electric field indicates participation of the collective state in formation of the energy levels inside the Peierls gap.