Exceptionally Slow, Long-Range, and Non-Gaussian Critical Fluctuations Dominate the Charge Density Wave Transition.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Phase Transitions

Background:

• Quasi-one-dimensional (TaSe_{4})_{2}I exhibits a well-known charge-density wave (CDW) transition near 263 K.
• CDW critical fluctuations are coupled to normal carriers, influencing resistance noise.

Purpose of the Study:

• To investigate the relationship between resistance noise and critical fluctuations of the CDW order parameter in (TaSe_{4})_{2}I.
• To demonstrate that resistance noise can quantitatively probe CDW critical phenomena.

Main Methods:

• Analysis of resistance noise measurements near the CDW transition temperature.
• Characterization of noise variance and relaxation time as a function of reduced temperature (ϵ).
• Investigation of the fluctuation distribution and its deviation from Gaussian behavior.

Main Results:

• Critical fluctuations of the CDW order parameter dominate low-frequency resistance noise over a wide temperature window (ϵ≈±0.1).
• Observed critical opalescence and critical slowing down phenomena.
• Demonstrated quantitative extraction of critical exponents from resistance noise.
• Identified a crossover from mean-field to fluctuation-dominated regimes with anomalously low critical exponents (|ϵ|≲0.02).
• Observed non-Gaussian fluctuation distributions, indicating a breakdown of the central limit theorem.

Conclusions:

• The quasi-one-dimensional nature of (TaSe_{4})_{2}I plays a crucial role in the observed large-magnitude critical fluctuations and the crossover behavior.
• Resistance noise serves as a powerful tool to study critical phenomena in CDW systems.
• The findings highlight the importance of dimensionality in controlling phase transitions.