Long-wavelength fluctuations and dimensionality crossover in confined liquids

Jing Yang; Yan-Wei Li; Massimo Pica Ciamarra

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arXiv · 2107.12225

Long-wavelength fluctuations and dimensionality crossover in confined liquids

Jing Yang·Yan-Wei Li·Massimo Pica Ciamarra

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Abstract

The phase behavior of liquids confined in a slit geometry does not reveal a crossover from a three to a two-dimensional behavior as the gap size decreases. Indeed, the prototypical two-dimensional hexatic phase only occurs in liquids confined to a monolayer. Here, we demonstrate that the dimensionality crossover is apparent in the lateral size dependence of the relaxation dynamics of confined liquids, developing a Debye model for the density of vibrational states of confined systems and performing extensive numerical simulations. In confined systems, Mermin-Wagner fluctuations enhance the amplitude of vibrational motion or Debye-Waller factor by a quantity scaling as the inverse gap width and proportional to the logarithm of the aspect ratio, as a clear signature of a two-dimensional behaviour. As the temperature or lateral system size increases, the crossover to a size-independent relaxation dynamics occurs when structural relaxation takes place before the vibrational modes with the longest wavelength develop.

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Jing Yang, Yan-Wei Li, Massimo Pica Ciamarra. 2021-07-26. Long-wavelength fluctuations and dimensionality crossover in confined liquids. https://arxiv.org/abs/2107.12225

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