Electronic states inside the gap of quasi-one-dimensional conductor NbS_3(I)

TL;DR

This study investigates the electronic states within the energy gap of NbS_3(I), revealing spectral features and continuous states that suggest the presence of defect-related and midgap states affecting photoconductivity.

Contribution

The paper provides new spectral data on in-gap states of NbS_3(I) and links specific features to stacking faults and midgap states, advancing understanding of its electronic structure.

Findings

Identified a peak at 0.6 eV near midgap with field-dependent amplitude

Observed a peak at 0.9 eV attributed to stacking faults

Detected continuous states between 0.6-0.8 eV causing bleaching effects

Abstract

The photoconductivity spectra of NbS_3 (phase I) crystals are studied. A drop of photoconductivity corresponding to the Peierls gap edge is observed. Reproducible spectral features are found at energies smaller the energy gap value. The first one is a peak at the energy 0.6 eV that is close to the midgap one. It has a threshold-like dependence of the amplitude on the electrical field applied. Another feature is a peak at the energy 0.9 eV near to the edge of the gap. We ascribe the origin of this peak to the stacking faults. The third one are continuous states between these peaks at energies 0.6-0.8 eV. We observed bleaching of the photoconductivity even below zero at this energies in the high electric field (700 V/cm) and under additional illumination applied.