Photoconduction in the Peierls conductor monoclinic TaS3

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 (m-TaS 3 ) and orthorhombic (o-TaS 3 ) samples the following new peculiarities of photoconduction in 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∆ * = 0.18 eV.

Charge-density waves physics revealed by photoconduction

“…The first photoconduction spectra measurements gave evidences of existence of relatively narrow peaks in o-TaS 3 [7], the amplitude of some of them being dependent on a relatively small electric field E ∼ 10 − 100 V/cm [7,8].. Somewhat similar peaks were also found in NbS 3 (I) in the middle of the optical gap at 0.6 eV and near the temperature-dependent edge at 0.9 eV [8] and quite recently in m-TaS 3 [5]. Similar peaks are also observed in the bolometric spectra of o-TaS 3 [17,18].…”

“…[9]) and monoclinic modifications of TaS 3 (Fig. 2, see also [5]). Qualitatively, such a complex behavior corresponds to the competition between at least two physical mechanisms working in opposite directions.…”

“…As the LEDemitted light power is controlled by the current flowing through the LED, the light intensity control is also simple. This method was widely used for investigation of the temperature and time evolution of the photoconduction current in q-1D conductors [2,3,4,5].…”

Tunable charge density wave in TiS 3 nanoribbons

“…Here, we use the maxima from the derivative curve. [29] to estimate the transition temperature of 29, 53, and 103 K in the 50 nm ∼ 60 nm-thick nanoribbon, which are similar to that of the bulk crystals. [23] Instead of showing a cusp, one observes a broadened maximum, which is consequence of fluctuations caused by the 2D dimensionality.…”