Evidence for a stress-induced incommensurate-to-commensurate charge-density-wave transition inTaS3

Abstract

We have measured the nonlinear conductivity, the thermopower, and the narrow-band noise in TaS3 as a function of elastic strain e along the chain axis. Both the thermopower and the chargedensity-wave (CDW) conductivity are dependent on the temperature and c. history of the sample. There are indications that the CDW becomes commensurate at @=0. 5%, where (at most temperatures) (1) there is a maximum in the threshold field for nonlinear conductivity, (2) there are anomalies in the thermopower and resistance, and (3) the narrow-band noise disappears.

Quantization of states and strain-induced transformation of charge-density waves in the quasi-one-dimensional conductorTaS3

“…2 shows typical strain dependence of conductivity of a TaS 3 sample at T=123 K for relatively low values of . In agreement with [3,4,5] the conductivity grows with ; the average slope of the curves ("gauge factor" of TaS 3 ), dln/d~100, also agrees with the previous studies. The obvious feature of the dependence is the hysteresis.…”

“…The quasi one-dimensional conductors, which are well-known firstly owing to the non-linear charge-density wave (CDW) transport [1], show also unique properties, which, to wide extent, can be called mechanical, namely: strain-induced features in conduction and thermopower [2,3,4,5,6], anomalous elastic [7,8,9,10,11,12,13,14], thermal-expansive [15] and electromechanical properties [16,17,18,19,20]. In particular, we can mention the abrupt changes in non-linear and linear transport under uniaxial stretch [3,4,5,6] accompanied with a feature in the stress-strain relation [14], drop of the Young modulus [7,8,9,11,12] and shear modulus [9,10,12,13] on the CDW depinning, hysteresis in thermal expansion [15], large electric-field-induced deformations (uniform [16] and non-uniform [17,18,19]). Generally speaking, all these features demonstrate interplay of the CDW and pristine-lattice properties.…”

“…The most detailed mechanics-related studies have been performed for TaS 3 [3][4][5][6][7][8][9][10][11][13][14][15][16][17][18][19][20][21], a typical Peierls quasi one-dimensional conductor with CDW forming at T P =220 K [1]. For this compound an integral picture of the lattice-CDW interplay has been arranged.…”

“…For this compound an integral picture of the lattice-CDW interplay has been arranged. The basic point of this picture is that under uniaxial stretch the q-vector (namely, its longitudinal component) reduces; at a critical stretch,  c , q achieves 4-fold commensurability with the lattice, i.e., shows a lock-in transition; at > c it is supposed to reduce further [3,4,5,6]. This inference has been based on a number of experiments: pronounced features in conductivity (both linear and non-linear) and thermopower are observed around = c .…”

Wide-temperature-range dielectric response of the charge-density-wave systemTaS3

“…In the same temperature range the stress dependence of the linear conductivity disappears. 24 By adding that the thermopower changes sign 25,26 at 70 K and the shear compliance has been shown to decrease substantially 27 below 50 K, we have exhausted the phenomena pointing to the change of the CDW properties around 70 K (ϷT P /3).…”