Evidence of Collective Charge Transport in the Ohmic Regime ofo−TaS3in the Charge-Density-Wave State by a Photoconduction Study

Abstract

Using photoconduction techniques, we demonstrate that the low-temperature Ohmic conduction of o-TaS3 is not provided by band motion or hopping of single-particle excitations-electrons and holes excited over the Peierls gap. Instead, the low-temperature Ohmic conduction is mostly provided by collective excitations having an activation energy much less than the Peierls gap value and shunting the contribution of electrons and holes responsible for photoconduction.

Charge density wave soliton liquid

“…Solitons have been expected to exist in the commensurate CDW of an o-TaS 3 system from electrical transport and optical excitation experiments [2,3]. The existence of a fractional 2π/M phase soliton (with a fractional charge 2e/M) is predicted in commensurate CDW systems with commensurability M, where M = 4 for o-TaS 3 systems.…”

“…Phase solitons have been expected in the one-dimensional CDW system of orthorhombic tantalum trisulfide (o-TaS 3 ) crystals to explain the CDW transport properties [2][3][4], and the Aharonov-Bohm interference in o-TaS 3 rings [5,6]. In addition, the coexistence of commensurate and incommensurate CDWs in o-TaS 3 crystals was observed below the Peierls transition temperature T P = 218 K by X-ray diffraction [7].…”

Optical selection of a multiple phase order in the charge density wave condensateo-TaS3using a spectrally resolved nonequilibrium measurement

“…At lower temperatures than T CDW / 2, several remarkable changes occur; a deviation from the activation law in linear conductivity, and the appearances of the second threshold, subgap structure, and new resonance, respectively, in nonlinear conductivity, 9 tunneling spectroscopy, 17 and dielectric spectroscopy. [11][12][13]18 In the similar temperature region, a splitting of satellite peak was also observed in a synchrotron x-ray measurement, 19 suggesting a coexistence of different CDW phases. The dielectric measurement provides evidence of two glass transitions at T ϳ 40 and ϳ10 K.…”

“…I, below T CDW / 2, the appearance of a new ordered phase has been suggested in various spectroscopic measurements. [11][12][13][14][15][16][17][18][19] For example, interlayer tunneling spectroscopy clearly indicates the existence of subgap states ͑amplitude soliton states͒ inside the CDW gap for NbSe 3 and TaS 3 . 17 Therefore the oscillatory resonances are associated with the optical transitions from the states formed by the commensurability.…”

“…[8][9][10][11][12][13][14][15][16][17][18][19][20] Below the phase-transition temperature ͑T CDW ͒, a Peierls gap opens at the Fermi level, resulting in a change of the conductivity from metallic to semiconducting. At lower temperatures than T CDW / 2, several remarkable changes occur; a deviation from the activation law in linear conductivity, and the appearances of the second threshold, subgap structure, and new resonance, respectively, in nonlinear conductivity, 9 tunneling spectroscopy, 17 and dielectric spectroscopy.…”