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Edited by Eric R. Weeks, Emory University, Atlanta, GA, and accepted by Editorial Board Member Pablo G. Debenedetti October 1, 2019 (received for review May 30, 2019)
Significance
Long-wavelength elastic modes, which have an infinitesimal energy cost, destroy the long-range translational order of 2D solids at finite temperatures. Here we demonstrate that these long-wavelength fluctuations also influence the dynamical properties of 2D systems in their normal liquid regimes. Hence, long-wavelength fluctuations make 2- and 3D molecular particulate systems behave differently from high- to very low-temperature regimes.
Abstract
In 2-dimensional systems at finite temperature, long-wavelength Mermin–Wagner fluctuations prevent the existence of translational long-range order. Their dynamical signature, which is the divergence of the vibrational amplitude with the system size, also affects disordered solids, and it washes out the transient solid-like response generally exhibited by liquids cooled below their melting temperatures. Through a combined numerical and experimental investigation, here we show that long-wavelength fluctuations are also relevant at high temperature, where the liquid dynamics do not reveal a transient solid-like response. In this regime, these fluctuations induce an unusual but ubiquitous decoupling between long-time diffusion coefficient D and structural relaxation time τ, where
Footnotes
- ↵1To whom correspondence may be addressed. Email: massimo{at}ntu.edu.sg.
Author contributions: K.Z., T.G.M., and M.P.C. designed research; Y.-W.L., C.K.M., Z.-Y.S., and R.G. performed research; and Y.-W.L., K.Z., T.G.M., and M.P.C. wrote the paper.
The authors declare no competing interest.
This article is a PNAS Direct Submission. E.R.W. is a guest editor invited by the Editorial Board.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1909319116/-/DCSupplemental.
Published under the PNAS license.
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Long-wavelength fluctuations and anomalous dynamics in 2-dimensional liquids
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