Strain-induced transformation of charge-density waves and mechanical anomalies in the quasi one-dimensional conductors TaS_3 and K_{0.3}MoO_3

TL;DR

This study investigates how strain affects charge-density waves and mechanical properties in quasi-one-dimensional conductors TaS_3 and K_{0.3}MoO_3, revealing strain-induced CDW transformations and anomalies in their conductivity and elasticity.

Contribution

It provides new insights into the strain dependence of charge-density wave wave vectors and mechanical anomalies, challenging traditional lock-in transition models.

Findings

Strain causes hysteresis in conductivity of TaS_3 and K_{0.3}MoO_3.

Nano-sized TaS_3 shows step-like changes in conductivity related to wave vector quantization.

The charge-density wave wave vector increases with sample expansion, contrary to traditional expectations.

Abstract

We report studies of low-field conductivity, sigma, of the orthorhombic TaS_3 samples as a function of strain, epsilon. In the Peierls state the sigma(epsilon) dependencies show hysteresis. A similar hysteresis loop is observed for K_{0.3}MoO_3. For nano-sized TaS_3 samples the sigma(epsilon) curves show step-like changes associated with the "quantization" of the wave vector, q, of the charge-density wave (CDW). The dependences clearly reveal the change of the q-vector with strain. In contrast with the traditional concept, q is found to increase with sample expansion. This means that the stretch-induced anomalies cannot be explained by the transition of the CDW to fourfold commensurability with the pristine lattice (lock-in transition). Alternatively, we suppose, that at the critical stretch a CDW with larger amplitude and modified q-vector forms. Further, the models describing metastable length states and drop of the Young modulus on CDW depinning in terms of longitudinal CDW strain, require reconsideration. Presumably, transverse effects should be taken into account.