Photoconduction in the Peierls conductor monoclinic TaS$_3$

TL;DR

This study investigates photoconduction in monoclinic TaS$_3$, revealing temperature-dependent activation energy, a shift in recombination mechanisms, and a detailed electric-field response, with spectral analysis confirming a Peierls gap of 0.18 eV.

Contribution

It provides the first detailed analysis of photoconduction peculiarities in monoclinic TaS$_3$, highlighting new mechanisms and spectral properties distinct from orthorhombic samples.

Findings

Photoconduction observed below 70 K with strong sample dependence.

Recombination mechanism shifts from linear to collisional at low temperatures.

Spectral analysis determines the Peierls gap as 0.18 eV.

Abstract

Photoconduction in the monoclinic phase of quasi-one-dimensional conductor TaS$_3$ has been observed at $T < 70$~K. It was studied jointly with low-temperature ohmic and non-linear dark conduction. The strong sample quality dependence of both photoconduction and dark conduction at this temperature region has been observed. Together with a similarity of the main features of the photoconduction characteristic of both monoclinic ({\it m-}TaS$_3$) and orthorhombic ({\it o-}TaS$_3$) samples the following new peculiarities of photoconduction in {\it m-}TaS$_3$ were found: 1) the dependence of the activation energy of photoconduction on temperature, $T$, 2) the change of the recombination mechanism from the linear type to the collisional one at low $T$ with a sample quality growth, 3) the existence of a fine structure of the electric-field dependence of photoconduction. Spectral study gives the Peierls energy gap value $2\Delta ^*= 0.18$~eV.