Hysteresis in thermal expansion of the quasi 1-dimensional conductor TaS3: Coupling of the underlying and the electronic crystals

An interferometer-based setup for measurements of length of needle-like samples is developed, and thermal expansion of o-TaS3 crystals is studied. Below the Peierls transition the temperature hysteresis of length L is observed, the width of the hysteresis loop $\delta L/L$ being up to $5\times 10^{-5}$. Curiously, $L(T)$ changes so that it is in front of its equilibrium value. The hysteresis loop couples with that of conductivity. With lowering T the charge-density waves' (CDW) elastic modulus grows and at 100 K becomes comparable with that of the lattice Yl. The results justify the assumption about the strain dependence of the CDW wave vector and clarify the nature of the anomalies of Yl which occur on the CDW depinning. In particular, Yl, is expected to show a strong drop in the static regime, if measured at sufficiently small sample elongation $(\delta L/L < 10^{ -5}) $.