1/f noise in a one-dimensional charge density wave system

– The current noise in a classical one-dimensional charge density wave system is studied in the weak pinning regime by solving the overdamped equation of motion numerically. At low temperatures and just above the zero-temperature depinning threshold, the power spectrum of the current noise S(f) was found to scale with frequency f as S(f) ∼ f−γ , where γ ≈ 1, suggesting the existence of flicker noise. Our result is in agreement with experimental findings for quasi–one-dimensional charge density wave systems and provides the first evidence of 1/f behavior obtained from first principles. Introduction. – The noise in any system is characterized in terms of the shape of its spectral power density S(f), which may be measured directly in experiments. If S(f) ∼ f−γ and γ ≈ 1, then such a noise is referred to as 1/f or flicker noise. Its existence has attracted the attention of researchers from various branches of the natural sciences for many years. As for physical systems, 1/f noise has been observed as fluctuations in the currents of diodes, vacuum tubes and transistors, the resistance of carbon microphones, metallic thin films and semiconductors [1–3], the magnetization in spin glasses [4] and in many other systems. Despite a substantial amount of experimental and theoretical effort, a unique underlying mechanism for the flicker noise remains unknown and still poses an open question as to its universal origins [5–7]. However, there is now increasing evidence that the non-trivial exponent, at least in electronic systems, may come from equilibrium dynamics in the presence of disorder [8] when energy barriers exceed the typical thermal energy. 1/f noise in charge density wave (CDW) systems [9] has been studied mainly in NbSe3 and TaS3 materials [8]. The first experiment was done on a bulk NbSe3 sample by Richard et al. [10] who found γ ∼ 0.8. Studying transport properties of the quasi–one-dimensional CDW material TaS3 at low temperatures, Zaitsev-Zotov [11] observed that slightly above the depinning threshold of the driving electric field, the exponent γ for the current noise is equal to γ ≈ 1.2.